Final Report and Recommendations for development of the Silver filter workshop – Yemen

GTZ-Integrated Water Resources Management, (IWRM) is involved in projects concerned with water management in Yemen. This project’s involvement with traditional Yemeni potters began to encourage the production of irrigation pots as a tool to reduce the amount of water used in farming in water poor Yemen. At the same time there was interest in the introduction of Ceramic Water Filters. (CWF) 500 water filters had been imported into the southern Shabwa Province with very good acceptance amongst the recipients. (These 500 filters were produced at workshops originally set up by Potters For Peace for IDE Cambodia.) It was felt that a combination of CWF, irrigation pots, with traditional and non-traditional pottery could diversify and strengthen the income of a potter family of potters willing to enter into a relationship with GTZ was identified before my arrival.

The Salman pottery workshop in Sana’a Yemen is located in a rural area of the city. This workshop entered into a relationship with GTZ earlier this year. Mr. Richard Boni working for GTZ has coordinated this relationship along with Mr. Michael Klingler of GTZ Integrated Water Resources Management. The Salman family lives at the workshop and includes Ali Saleh Said Salman, Ali’s father-Saleh Said Salman, Ali’s brother- Muntesar Saleh Said Salman, cousin Tewfik Ali Yahya Azizzi, Selam Sale Said Salman Ali’s mother- Fatimah Ali Mahdi and Ali’s wife.

Some months before my arrival, a catenary arched downdraft kiln approximately 120 cubic feet in size (4 cubic meters) was designed and built for the workshop by Bernd Pfannkuchen through assistance by GTZ-(IWRM Yemen . The kiln is propane fired, which was considered the fuel of choice, because of the high cost of wood and charcoal. The size of the kiln reflects the need to accommodate tanoors, traditional Arab ovens, which are a substantial part of the production of the workshop. These ovens are made in a number of different sizes, the largest of which can be almost one meter in height and 50cm in diameter. When I worked in the pottery, the potters were in the midst of filling an order of tanoors as a partial repayment of loans advanced for the construction of the kiln and the purchase of the land.

The construction of the pottery workshop and compound is cement blocks with corrugated sheet metal roofing. When I arrived in early April the kiln had only been fired a few times.

The main production at the workshop is traditional Yemeni unglazed earthenware pots. The clay is mostly unrefined and prepared quickly by wetting the clay and foot wedging on the floor of the workshop. The pottery produces ware by coil and smear method, forming on plywood batts, which are set on platforms, usually old car tire rims. The potters form by walking around the developing forms (usually backward) while manipulating the clay in a series of deft processes akin to using a potter’s wheel: coiling and smearing until the basic form is begun, then paddling with a wooden form, drawing and evening the walls of the pot- next the form is thinned and drawn up and finally smoothing with a wet cloth. These potters are masters of this method of forming. They work as a family unit, father and sons sharing in all of the work. .

The production of ceramic water filters required changes throughout the workshop beginning from the clay preparation. Traditionally, clay is trucked in from the mine and deposited in an area adjacent to the workshop and left uncovered and open to the elements.

Normally clay for CWF must be dried and screened and put in sacks or otherwise covered to reduce variation caused by moisture. In Sana’a the dryness of the desert doesn’t seem to be much of a problem. Even on days when it rained, most of the moisture in the clay had evaporated within a couple of hours. Despite this, I feel it is important that the clay be carefully screened and sacked. Clay for traditional ware is not screened. The potters understand that the filters require screened clay but they may not yet see that this also affects the characteristics of the finished ware. Clay that is finer due to screening will form pots which are denser and therefore have less thermal shock qualities. For most pieces this doesn’t cause a problem but it may for tanoors. Not being familiar with the day to day use of a tanoor oven used in a traditional Yemeni kitchen, I do not know to what extent this will be a problem.

Before my arrival in Yemen instructions were sent to the pottery to prepare 50 sacks of screened clay and a large quantity of dried sawdust. A large cement block soaking tank was made for the flow testing of filters and colloidal silver was purchased for the treatment of fired filters. A log of activities was prepared as work progressed.

Upon my arrival in Yemen, Richard Boni and I spent more than a week modifying an existing mechanical press for forming ceramic filters from clay. After the press was prepared, the moulds were attached, and it was delivered to the pottery. The inability to find a clay mixer of an appropriate design meant that it was necessary to prepare the clay/sawdust mix by hand using plastic mixing buckets.

The screened dry clay and sawdust were first weighed using a gram scale and then dry mixed. The blended dry materials were then wet mixed, lightly wedged, and weighed again into 9kg batches.

Each of the filters was formed using the new press. The female mould was lined with a plastic bag and the male mould was also covered with a bag. These plastic bags act as separators and allow the filters to be released cleanly from the moulds. The 9 kg. Charge of the clay/sawdust mix was pressed into the bottom of the female mould and it was raised into position. A hydraulic jack was set into position on the press and the female mould was pressed up with20 tons of pressure. The top of the press frame is hammered with a rubber mallet to release the filters. Once the pressure was released, the female mould was lowered and the plastic liner was removed from the female mould. Next the inside of the now accessible new filter was fettled to smooth and correct any imperfections. The filter in the female mould is now raised again on the press and an ejector rod is placed into position and the new filter is ejected from the female mould by lowering it on the press. Finally the new filter is removed from the press. Each filter was carefully dried by loosening the remaining plastic bag from against the outside of the newly formed filter. The filters were carefully monitored to prevent them from drying too quickly in the arid desert air by keeping them loosely covered with plastic and then after uncovering them, by turning them upside down if the lips dry too quickly. Drying took 4 to 5 days.

Once dry, the filters were stacked in the kiln and fired to a target temperature of 900C. Information concerning firing can be found in the two excel documents-‘Sana’a Test Firing Curve’ and ‘April 28th 07 filter firing- Sana a’

Six different clay/sawdust ratios of filters were attempted. The formulations were dried and fired in the kiln. The results of this series of filter tests showed that the following mix produced the best flow rate results:

Mix #1

Formula Batch Wt.

Sana’a Clay- 95% 8550

Sawdust 5% 450

Total 100% 9000gr.

2.4liters of water

See word document – ‘Yemen Ceramic Water Filter Flow Test Results’

The average rate of water flow for this proportion was 2.33liters per hour. It must be remembered however that this flow rate was achieved at a temperature of between 915-923 degrees Celsius. If the temperature is lowered substantially from this, the proportion of sawdust to clay will need to be adjusted. I think that a target of 900 C. probably will not require adjustment however flow testing will determine this.

One Hour Flow test-After forming and firing to a temperature of between 912-923C most filters were soaked in water in the cement tank for more than twenty four hours. The filters were then filled with water and allowed to stand for one hour. The amount of water filtered was measured using a PVC tee shaped gauge. (See photos) The cement soaking tank needs to be kept full of water for a period of time and then rinsed out to clean out the fine silt which will become trapped in the pores of the new filters.

I would recommend that another batch series of filters be formed and tested. This will further refine the flow rates. A minimum of ten filters of Test A, B and C below should be fired and flow tested. Once this test is finalized and the final clay/sawdust proportion is decided upon, the workshop can translate the weight proportions to volume measurements with appropriate sized containers. This should considerably speed up the forming process.

Test A Formula Batch Wt.

Sana’a Clay- 96% 8640

Sawdust 4% 360

Total 100% 9000gr.

2.4liters of water

Test B Formula Batch Wt.

Sana’a Clay- 96.5 8685

Sawdust 3.5% 315

Total 100% 9000gr.

2.4liters of water

Test C Formula Batch Wt.

Sana’a Clay- 97% 8730

Sawdust 3% 270

Total 100% 9000gr.

2.4liters of water

Colloidal Silver Recommendations and Precautions

We conducted a training session on the application of Colloidal Silver (CS) Out of this session I have made a number of recommendations for the workshop

  • A room with shelves should be built for the storage of CS and dipping solution and utensils
  • Containers and Mixing implements should not be used for other purposes
  • CS should be kept in it s original container
  • When not in use CS dipping solution should be kept in a covered container
  • Mixing and application of CS must be done with protective gloves to limit skin contact
  • Clean up of containers and implements will result in contaminated cloth and water, this material should be disposed of in the latrine
  • Two persons should be designated for CS preparation and application
  • The next time that CS is applied to filters the methodology should be reviewed again especially the need to mix the solution properly before dipping
  • CS in the concentrated form used for application to filters can accumulate in the body , care must be taken to prevent contamination of the workshop environment, ground etc. These precautions should be reviewed the next time CS is applied to filters. These precautions should be provided in Arabic

Safety recommendations for the handling of propane

Propane is a not new in Yemen being produced there, but as a fuel for artisan potters it is. The sophistication of the firing system at the Salman workshop is well thought out. Of particular importance is the forethought of including small safety shut off valves on each burner. A problem of the gas system is that the removal and filling of the 16 gas cylinders requires careful monitoring to be certain that there are no leaks at the cylinder valve as well as at the hose clamps.

In a situation like this, where a number of small gas cylinders are teamed together to a manifold, the cylinders cannot be completely discharged because of the speed of gas withdrawal during the firing. The potters are understandably unhappy by the amount of gas remaining that they lose due to this. They have made attempts to withdraw this remaining gas from one cylinder to another. This is not a safe practice and they must be cautioned about this.

For a number of months before my arrival in Yemen attempts were made to locate both a hammer mill for crushing clay and a mixer for preparing the wet clay batches without success. An appropriate mixer design was shared with Nasser machine shop for quotation.

  • An appropriate clay mixer design may be found in the Adobe Acrobat 7.0 Document – clay mixer
  • Filters should be individually numbered tracking number while they are still in the mould This tracking number allows the workshop to better understand the success of the production process and it also allows for the systematic monitoring of the filters in the community. It is essential that the workshop record the sale of filters so that they may be followed. Filters formed for the test series were numbered by using iron oxide. A rubber stamp for numbering filters has been ordered for the workshop.
  • A health monitoring agency must still be identified for the field assessment of filters as soon as filters are ready to be sold. Potters Without Borders requests that GTZ inform us when this relationship is established so that we may assist with questions that may arise from the monitoring process
  • Presence/absence tests (P/A test) from Hach Company of Colorado were identified for the monitoring of filter’s ability to remove bacteria. The use of P/A tests were discussed and Richard Boni conducted the first test of water from a contaminated source to demonstrate the filters ability to eliminate bacteria

Conclusions after set up of the filter workshopThe conclusion of the ceramic water filter training now means that the Salman pottery workshop has the ability to form filters from locally available raw clays. The ability of the workshop to take this new capacity and deliver properly functioning ceramic water filters into the community will require careful follow.The Salman workshop will need support in order to be able to consistently reproduce filters with correct rates of flow. The Salman`s have a strong understanding of ceramic process. As an example within two weeks of first using the new ceramic filter press, the workshop adapted the forming process to simplify and speed up the forming of irrigation pots. Although I discussed the need for consistency in processing of raw materials and in the forming process I feel the workshop will need assistance to maintain this discipline and to make sure that all those being trained in the key processes of, material preparation, forming, firing, flow testing, and colloidal silver application are well prepared as well. Richard Boni has been instrumental in the members of the Salman workshop understanding and accepting these new technologies. His continued involvement in monitoring and assisting the workshop with scientific method is invaluable to the workshops success.A number of extensive studies on similar new ceramic water filter workshops indicate that the production of silver filters in Yemen will result positively impact the health of the end users. Water poor Yemen currently does not have the ability to service outlying communities with piped potable water. CWF is a credible technology that will deliver safe water to at risk communities with little waste. Potable water is produced directly in the homes of users without the need for separate extensive piped systems.

After the successful firing of filters, Richard and I went into the commercial areas of Sana’a and were able to find a plastic receptacle which fit the filters. Since then a second filter has been identified. The Salman workshop is also developing a receptacle made out of clay similar in design to traditional Yemeni water containers. Developing a number of receptacles at various prices will encourage the acceptance of CWF. GTZ has arranged for the translation of the cleaning protocols for the filters. Other CWF workshops have contracted plastic receptacles with both instructions and logo imprinted directly in the body of the plastic in so doing they create professional approach to the marketplace and speed up acceptance.

  • Production Forms for water filters-to follow
  • A computer assisted design(CAD) for a mechanical screen to prepare sawdust will follow

Download Document 49kb: burt-cohen-potters-without-borders-yemen-final-report-a.doc

GTZ Yemen Ceramic Water Filter Flow Test Results

GTZ Yemen Ceramic Water Filter Flow Test Results


6 -#1 Mix Filters 2.33 liters/hour average

10 – #2 Mix filters all more then 3.5 liters per hour

9- # 3 Mix Filters- All more then 3.5 liters/hour

1-#4 Mix Filter- More then 3.5 liters per hour

No # 5 Mix filters survived the forming process –due to fragility

4 -#6filters- All more then 3.5 liters/hour

Total Filters Flow Tested-30

Filters formed- 48

One Hour Flow test-After forming and firing to a temperature of between 912-923C most filters were soaked in water for more than twenty four hours. The filters were then filled with water and allowed to stand for one hour. The amount of water filtered was measured using a pvc tee shaped gauge which was set on the filters. (See photos)

Mix #1

Formula Batch Wt.

Sana’a Clay- 95% 8550

Sawdust 5% 450

100% 9000gr.

Of 6- Mix #1 Filters


2.5 liters

2.5 liters

2 liters

2 liters

2.5 liters

Flow Test-2.33 liters/hour average

Mix 2– 5% More clay then 50/50 Proportion

Formula Batch Wt.

Sana’a Clay- 90% 8100

Sawdust 10 900

100% 9000gr.

Flow test

Of 10- Mix#2 filters- All filters were more then 3.5 liters per hour

Mix 3– 50/50 Proportion by Volume

Formula Batch Wt.

Sana’a Clay- 85.6% 8127

Sawdust 14.4 1372

100% 9499gr.

3.5 liters water (estimated)

Flow test

Of 9- Mix #3 Filters- All filters were more than 3.5 liters/hour

Mix 4 – 5% Less clay then 50/50 Proportion

Formula Batch Wt.

Sana’a Clay- 80% 7136

Sawdust 20% 1784

  1. 8920

Flow Test

Only 1- Mix# 4 filter emerged from the mold intact, because of fragility-( One filter broke during flow testing) This filter was more than 3.5 liter/hour

Mix #5

Formula Batch Wt.

Sana’a Clay- 75% 6750

Sawdust 25% 2250

100% 9000gr

Flow Test-

No Mix#5 filters survived the forming process

Mix #6

Formula Batch Wt.

Sana’a Clay- 92.5% 8325

Sawdust 7.5% 675

100% 9000gr.

Flow test

Of 4 –Mix# 6 filters-all were more than 3.5 liters/hour

Download full document 34kb: yemen-ceramic-water-filter-flow-test-results.docyemen-ceramic-water-filter-flow-test-results.doc

April 28th 2007 filter firing Yemen GTZ

Time Description Door Bottom Door Top Chimney Side

Kiln On 4 corner burners

60 93 122

1:00 Damper at 10 cm 69 93 128

1:22 6 burners (2 more near to the door)

1:30 Damper @ 15 cm 93 118 156

111 133 170

173 195 248

3:35 Smoke beginning to generate from filters 187 209 265

3:40 Heavy smoke

208 230 307

4:23 smoke reduced 228 245 337

4:26 8 Burners Damper@ 24 cm

4:38 Damper @ 27 cm 293 295 388

5:00 10 Burners 345 317 415

347 401 448

5:22 12 Burners (2 on low)

417 401 457

438 480 465

6:41 All burners on low 474 518 481

504 536 501

7:00 Increase two burners either side of the door 509 537 509

539 575 530

7:32 Increase ten more burners 554 588 543

8:00 Increase ten burners again slightly more 610 646 602

8:22 Damper @ 24 cm 650 684 639

8:40 Increase 8 burners on chimney side to full on 675 708 684

9:00 Increase 4 burners on door side to full 712 744 717

9:12 All burners on full 729 763 738

750 779 755

9:45 Increased pressure on gas manifold by kiln 784 813 784

9:58 Switched propane cylinder bank to +pressure 798 830 804

10:05 Cone 013 down 012 bending

10:10 Cone011 Bending 832 862 836

10:12 Cone 011 @ 3 o clock

10:14 Cone 011 down 844 874 845

10:16 Open damper to 22 cm 848 877

865 891 867

871 897 874

10:35 Begin Soaking period 874 899 878

10:40 All Cones except 09 down -reduce pressure 877 901 881

10:52 increase pressure slightly to maintain pressure 880 903 885

upper Cone 09 @ 3 o clock

11:00 ` 883 906 888

885 906 890

880 902 886

11:39 Kiln Off

Notes on the Sana’a, Yemen filter firing April 28th, 2007
The firing of the ceramic filters followed a firing of tanoor ovens by two days insuring that the kiln was well dried.
In firing the filters I was particularly concerned that all of the sawdust would be completely burned out so that trapped carbon would not cause a problem with the filters. This is necessary so that the finished filter be as strong as possible and so that flow rates not be effected by carbon in the filter body. Care must be taken in the stacking of the filters in the kiln to separate the filters using spacers so that heat can infiltrate throughout the setting. Filters should not stacked bottom to bottom without spacers as well. The filters staked on the floor of the kiln should be stacked on top of brick to elevate them. Another thermocouple was installed near the floor of the door to monitor the difference in temperature between the floor and the upper part of the kiln. It is recommended that monitoring of the temperature advance is done with a combination pyrometer, Orton temperature cones and draw trials.

A warm up period with a target temperature of 300 Celsius in the first 4 hours proved adequate to insure both moisture and carbon was not trapped.
After the warm up, an advance of 100 C per hour was desired up until a target temperature of 900 C. In practice we took longer to advance in temperature due to the amount of smoke which was generated by the burning out of the sawdust . At target temperature the firing was soaked for one hour. I had intended to soak for a longer period as per advice by other filter technicians, but after discussion with Bernd Pfannkuchen the kiln designer, and through evaluation of the draw trials* at the target temperature I decided that one hour soaking was adequate. An examination of the finished filters showed that there was no trapped carbon. The original recommendation of a longer soaking period is based on the use of the Mani kiln which is using solid fuels (wood) whereas the Sana’a catenary kiln fires with Propane under oxidizing conditions. Having the designer of the kiln to assist in the filter firing was a real advantage. Bernd gave advice and the kiln design proved very versatile. It is noteworthy that the Orton cones and the pyrometers showed less then one cone differential in temperature throughout the kiln.
*The draw trials were made from the same mix of clay and sawdust and formed into rings. These trials were positioned in the kiln on two levels near the floor and withdrawn through the ports in the door. These rings were then examined for residual carbon as well as for strength.

Potters Without Borders Newsletter No.1

Issue No.1 – April 2007
P.O. Box 1006 Enderby, B.C. V0E 1B0 – CANADA

The Ceramic Water Filter

Greetings friends;

This is the first issue of the Potters Without Borders newsletter! A lot has happened since we started working towards the creation of this organization, and now we have the time to write about it.

Our first meeting was back in the spring of 2006, Reg Kienast, Joan Crebo, Don Pegg, Kai Morrill and Burt Cohen were there. The name of Potters Without Borders (PWB) was born, and along with the help of our other roaming board members Nicole Reidmuller in Vancouver and Samantha Sherer in Toronto we were able to lay the foundation for this new non-profit association.
A lot of brainstorming went on during that meeting to try and figure out what kinds of things were going to get into as an organization. Although we are still open to pretty much anything, this past year we have participated in projects principally related to fundraising and the development of Ceramic Water Filters and the technology involved in their production.

Fundraising efforts have been incredible. Last year we raised over $3500 with the help of private donations and a few dedicated volunteers.
It began in July of 2006 with the “Footprints” exhibition at the Roundhouse Community Arts Centre in Vancouver BC, where various ceramic artists auctioned original artworks in support of Potters For Peace and Potters Without Borders.
Shortly after, a group was put together to set up an information booth at the August, Komasket Music Festival in Vernon BC, the festival lasted for three days. This was the debut of the PWB raw cotton T-shirts, beautifully designed by Bill and Claire, members from up in Wells BC. The Ceramic Water Filter (CWF) display was well received and prompted many interesting discussions as well as garnering a few new members.
The booth worked so well we were then invited to present at the Roots and Blues festival in Salmon Arm BC, another three day event which was a great success. We sold piles of shirts and brochures, I couldn’t believe how many interested folks would wander up to have a chat, we might have to go back!
The March Silent Auction at the Shooglenifty dance and concert in Salmon Arm BC, was a great success. We want to thank the incredible artists who donated their beautiful works to this event, we raised over $1000!
This year we will have further opportunities to raise money in support of the kinds of projects you’ll read about below, and also to explore new possibilities in other areas.

Last August PWB sent Burt Cohen (one of PWB’s directors) off to Calgary AB to meet with the members of the Centre for Affordable Water and Sanitation Technology (CAWST). Here we were able to help compare the various benefits of various methods of water sanitation and learn more about where our CWF technology fits into the big picture. Some important contacts were made and much information exchanged.

Burt also worked as a technical adviser to the Colombian Ceramic organization Artierra during February and March of this year. This assignment was undertaken through the generous support of the organization Canadian Executive Services Overseas (CESO) and their Colombian counterpart FICITEC, as a part of their Volunteer Assistance Program. Burt worked with seven pottery workshops in various aspects of production including kiln firing, clay, glazes, and forming processes. At the same time he was doing groundwork for a new CWF production workshop in Colombia to be sponsored by Oxfam, thanks Burt.

Since October of last year PWB has put significant effort into improving the design of the Dutch hydraulic filter press. After many weeks of patient laboring and the help of master machinists Art Gavel and Barry Cawston a new model, now referred to as the PWB double scissor press, was born. This press is made from very basic steel materials, using a 20 tonne jack, and two machined aluminum moulds. Thanks to Ben Morrill you can go to the PWB website to see a video of the press in action, as well as various schematics for its reproduction.
The press was put to use right away and the Northfire Pottery studio at O’keefe Ranch in Vernon BC, became a research facility. Engineering students working with Professor Frank Shih from Seattle University came up to produce the first in a series of test batches designed to experiment with CWF production. These students will be continuing their research as part of their senior projects.
The research facility in Vernon will continue to explore various potentials in the creation of Ceramic Water Filters, we are doing our best to publish all of our findings to the PWB website for public perusal.
In April Potters Without Borders will cooperate in the development of a CWF workshop in Sanaa, Yemen. At the request of the German non-governmental organization GTZ we will send a technician to Africa in order to assist in the implementation of a CWF production facility. We will be using the PWB press in a practical in the field situation, very exciting.

We have been making our presence known at the National Council on Education for the Ceramic Arts (NCECA) Confrence in the United States. Sending a representative to this type of international convention has been an important way for our organization to make contacts in all areas of the ceramic industry. These contacts often lead to overseas contracts for PWB. The NCECA website is:
We are also assisting with Gonzaga University’s Department of Engineering in their efforts to develop a CWF filter factory in Benin this year.
Kai Morrill has been in Brazil and is investigating a possible partnership with another ceramics NGO in order to participate in projects for children.

Remember that research results, documents, and articles regarding Ceramic Water Filter (CWF) technology and Potters Without Borders activities are available for reading at, just click on DATABASE to see the articles. If there is anything you think we should include on the website, or in this newsletter, please contact me at

Enjoy springtime!
Kai Morrill

Download PDF:

Potters fired up about clean water

By kristin froneman Morning Star Staff Jan 24 2007
Photo: Lisa vandervelde/morning star

Burt Cohen helps University of Seattle mechanical engineering student Andrew Lybarger create a ceramic water filter.

For the past 15 years, Burt Cohen has entertained visitors by throwing some clay on a wheel and heating up his kiln to make bowls, mugs and plates at his pottery studio at O’Keefe Ranch. However, this past weekend, Cohen opened his studio to work on a project that goes beyond art, one that will affect people’s lives in developing countries that go without clean drinking water.

A group of engineering students from Seattle University were at the ranch to learn about a ceramic water filtration project, and specifically how the filters are made. Found to be an effective method to clean out the four most common water-borne diseases – E. coli, giardia, cholera and cryptosporidium – the filters are part of a global-scale project Cohen has been working on as a founding member and principle director of Potters without Borders.

“The WHO (World Health Organization) has come up with a protocol to deal with problems with water by 50 per cent by 2015,” said Cohen. “In Vancouver, two million people had no access to clean water without going to commercial means. “We are riding on a crest of need. In the last year, we have had many requests to set up ceramic water filter factories around the world.”

Cohen’s involvement withceramic water filtration came after he joined Potters for Peace, an international non-governmental and non-profit organization. His work as a production potter had already taken him around the world. He worked in India and immigrated to the North Okanagan from Japan in the late-’70s. “I came out of the technical side of things. I am trained in small industry and was a kiln builder by trade,” said Cohen. Potters without Borders, which was modelled after Potters for Peace, was founded by Cohen and six other individuals from B.C. a year ago. “There were some things we could do here in Canada that the international organization, which is based in the U.S., could not, including work in Cuba… We have a little more freedom,” said Cohen.

It has been a busy few months for Potters without Borders, which has received a number of requests to develop ceramic water filter manufacturing facilities overseas. “We have an open source philosophy… Anyone can make the filters. We give them the assistance to form a facility,” said Cohen. “We don’t make the filters to send to them. We provide the expertise and cause for the filters to be made there. We also give them the protocol, and assistance and monitor the filters once they are up and running.”

The filters are made from source clay and mixed with a noncombustible material such as sawdust (rice husks have been used in Southeast Asia). All the material is then dried and screened, and put into a mixer with water until it is blended into a plastic consistency. It is then weighed, placed into a mould, and pressed under a heavy weight using a hydraulic press. The finished form is then dried and fired to 850 to 950 degrees Celsius, which Cohen says is cold for ceramics. When the filters emerge, they are float tested and made sure the water travels through them removing the harmful bacteria.

Cohen has developed a research station at his O’Keefe Ranch studio, and has developed relationships with two universities in Washington state, Seattle and Gonzaga in Spokane, to develop and work on aspects of the technology, hence, the weekend workshop with the Seattle students. “Professor Dr. Frank Shih at the Seattle University College of Engineering has been my liaison for this research,” said Cohen. “We have given them a list of our research needs, and they have chosen an area they want to work with. “(The students) are addressing the area of combustible material. And in order for them to do their research, they needed to learn how to form the filters, and that’s why they were here.”

Cohen has also spoken to medical doctor William Duke at the University of Victoria, who had agreed to assess the filters. “He will tell us what we are doing right, and what we are doing wrong.” The members of Potters without Borders, which just received non-profit status from the province, are not compensated for their work, and depend on donations to their foundation. “We’ve been pushed very fast into this the last year. We can use as much material assistance as possible,” said Cohen. Those wanting more information on Potters Without Borders can go to the Web site at A silent auction of mainly pottery will also be held to support the organization during the Salmon Arm Roots and Blues Shooglenifty concert, March 30 at the Salmon Arm Rec Centre.

© Copyright 2007 Vernon Morning Star

PWB Front page Potters Guild Newsletter

Attached find the latest newsletter from the BC Potters Guild, just published. They have featured Potters Without Border on the cover. This is quite a boost to out profile in the Province and I have great hope that this will create a lot of interest for us as well as water filter projects. Steel for the new filter press has been ordered and arrives on Friday. Two mechanics, Art Gavel and Barry Cawston have agreed to help machine, assemble and modify the design for our purposes so that we can begin forming filters this month here in the Okanagan. On the 11th I meet with students from Gonzaga University on Spokane who are also going
to be producing filters in preparation for a project in Benin, West Africa.Stay warm


Download newsletter PDF 1.2MB: Nov06PGNL.pdf

Open Letter

Potters Without Borders was formed out of our desire to establish a Canadian organization as a part of an international non-profit network capable of providing socially responsible assistance to pottery groups and individuals. This summer, a group of like minded friends, worked to establish PWB as new non-governmental organization. We provide support to field technicians who respond to direct requests to develop ceramic water filter manufacturing facilities overseas. We also offer technical training and consulting services and facilitate research, development, and commercial application of technology in the field of ceramics in developing countries.

Since our recent beginning, Potters Without Borders has been busy. We were involved in the World Urban Forum and the World Peace Forum in Vancouver in June organized by Nicole Riedmueller.( This has resulted in our developing a Vancouver based chapter. We also had information booths at the Komasket Music Festival in Vernon, BC, as well as the Salmon Arm Roots and Blues Festival this summer in the Okanagan.

We are excited to be involved with research and promotion of ceramic water filters. These filters are a result of a marriage of two known technologies, porous ceramic and colloidal silver. The filters make bacteria free water economically with indigenous materials. A portion of Northfire Pottery workshops at the O´keefe Historic Ranch outside of Vernon, is now used for ceramic water filter research and development. We have now entered into relationships with the engineering faculties of both Seattle University and Gonzaga University in Spokane. In August, we were invited by Derek Baker to conduct ceramic water filter training at The Centre for Affordable Water and Sanitation Technology (CAWST) in Calgary Alberta and exchanged ideas on the promotion of Household Water treatment.

Take a moment and visit our website, there you will find links to our very experienced sister organization, Potters for Peace- as well as information about our work in Guatemala and Nicaragua. Our organization is committed to an open source philosophy; all of our publications are available to any interested parties I hope that you will consider supporting us and becoming involved. Contact us directly at:

Potters Without Borders

Po box 1006

Enderby, BC Canada V0E 1V0


CAWST Conference in Calgary AB

In August of this year Potters Without Borders and Potters For Peace were invited by the Calgary-based Centre for Affordable Water and Sanitation Technology (CAWST) to demonstrate the methods used to produce Microporous Ceramic water filters. Ron Rivera from Potters for Peace and Burt Cohen from Potters Without Borders spent five days discussing and running a workshop on the processes involved. In addition our organizations familiarized each other with the the areas in the world where we work as well all of our local partners to see if there might be ways in which we could cooperate.
CAWST is primarily involved in the training and promotion of bio sand filters, but we are all involved with household water treatment technologies that are working towards similar goals, that of producing safe clean water. During our time in Calgary efforts were made to understand each others approaches and see how we could perhaps integrate the other technologies. While there we formed a number of ceramic water filters using a set of molds supplied by Potters for Peace. Other porous filter techniques were also reviewed.

We were impressed by CAWST´s abilities and effectiveness in promotion, training and experience in the field. They have a mature organization with resources that we hope can help Potters Without Borders to be taken seriously in the field of Household water treatment. Because of our commitment to an open-source philosophy we will share our work with like minded groups like CAWST.


Download document with images: CAWST.doc

USAID Hygiene Improvement Project E-Conference

E-conference 2006 May 12 – 22: Household Water Treatment and Storage
Household water treatment and safe storage (HWTS), together with provision of an improved water supply, adequate sanitation and hand washing promotion are highly effective interventions receiving increased attention of donors and implementers. From May 12-22, HIP held an e-conference that discussed two themes simultaneously on parallel tracks: 1) Household Water Treatment and Safe Storage: What can the poor afford? 2) How do programs promote water treatment and ensure that the government continues to supply improved drinking water sources?

FileHWTS E-Conference Summary
This document synthesizes the e-conference discussions .

POU E-conference Synthesis 5-06.doc (329 kB)

IDEASS filter publication

Innovation for Development and South-South Cooperation (IDEASS Nicaragua)
This is a presentation by Ron Rivera combining many areas of supportive research towards CWF Filtron.
12 pages, useful images, bacteriological test chart, sanitation methods comparison chart, manufacturing process explained.

Download pdf document 308kb : UN filter publication.pdf


August 4, 5 & 6, 2006
Komasket Park, Vernon, BC Canada


We put together an information booth last weekend for presentation at the Komasket Music Festival. Using information gathered from other websites, and CWF (Ceramic Water Filter) documents provided by Burt we made up some full color posters. The entire “Komasket Publicity Package” can be found below for download.

We were able to sell a few “Potters for peace” T-shirts, and add a number of contacts to our E-mail list. Most importantly we connected with many people who are interested in the CWF technology and made our name “Potters Without Borders” known to a new community.

Burt made a beautiful receptacle for the filter, which prompted many inquiries about the filters availability here in Canada. It seems that the idea of having a countertop water filter is just as appropriate in the Okanagan Valley where clean, healthy drinking water is becoming scarce. Especially as an alternative to bottled water which has become the “norm”, the CWF is a way to have clean water without chlorination. Could we produce a filter here and use the profits elsewhere?

Komasket Publicity Package:

cartoon.jpg : 300kb – Cartoon of Filtron, by Santec, Cuba (Color 8.5×11)
logo1lg.jpg : 1.05mb – PWB logo, (B/W 11×17)
mission.pdf : 13kb – Preliminary mission statement (to be revised), (B/W 11×17)
press poster copy.jpg : 1mb – Glossy poster of filter presses from 5 countries (Color 11×17)
RDI Display.pdf : 241kb – 2 page explination of the entire filter production process with photos of every step taken from the RDI website (Color 8.5×11)

The International Network to Promote Household Water Treatment and Safe Storage

A major burden
Every year there are 1.6 million diarrhoeal deaths related to unsafe water, sanitation, and hygiene—the vast majority among children under 5. More than one billion people lack access to an improved water source.

Link to full article:

Capabilities and Short History of the Filtron Design Ceramic Water Filter (CWF)

The water filter design that is now used in Nicaragua was invented by a Guatemalan chemist, Fernando Mazareigos.   This design was the first that we know of where the capabilities of a ceramic filter were combined with the antimicrobial capabilities of colloidal silver. 

 In 1981, the InterAmerican Bank financed a comparative study to determine which of ten appropriate technology filters best met the following criteria:


 Has a sufficient flow rate for home use

 Is effective at removing bacteria

 Is simple to manufacture

 Can be made with available materials

 Can be made and sold at low cost

 Contributes to economic activity at low-income level

 Ease of distribution

Download Full Document: Capabilities of the Filter.doc

Problems in the Field and Solutions

The most basic of all problems with regard to “filter” use comes from the choice of words. In some information given out by PFP/Filtron, and in studies conducted in the field, clear distinctions were not made between the filter element (the filter that is made of clay and coated with colloidal silver), the receptacle (the plastic bucket or clay receptacle in which the filter element sits), and the complete product called Filtron in this manual…

Download Full Document: Problems in the Field.doc

Potable Water, Purified Water, and Water Treatment Processes

Potable Water can be described as all water used for human consumption that does not pose a health danger and which is microbiologically safe and free of all pathogenic microorganisms and bacteria associated with fecal contamination. In the United States, according to the U.S. Environmental Protection Agency (USEPA) it is water with (0) fecal coliforms, (0) Giardia lamblia, (0) Legionella, (0) enteroviruses. According to the World Health Organization (WHO) Guidelines for Drinking Water Quality (2002), “E.Coli or thermotolerant coliform bacteria must not be detectable in any 100 ml sample.” It can be produced by any method or can be naturally occurring.

Download Full Document: Methods of treatment Point of use.doc

Follow Up Field Report

Report on follow-up training to accompany Filter projects in the field.

Potters for Peace and the Filtron workshop in Nicaragua have produced over 20,000 colloidal silver impregnated ceramic water filters (Filtrons). The majority of these Filtrons were purchased and distributed by non-governmental organizations (NGOs) throughout rural Nicaragua. The Filtron consists of a filter that sits in a clay or plastic receptacle. Though laboratory testing of the ceramic filters showed a consistent 98% to 100% removal of bacteria, field studies revealed bacterial recontamination of water in up to 80% of water sampled from the filter receptacles. This can be largely attribute to bad cleaning practices, incomplete or inaccurate training of NGOs distributing the filters, and a general lack of understanding on the part of both rural health promoters and users about how the filter works, required maintenance, and the nature and origin of waterborne disease.

Download full document: Field report on filters use.doc

Colloidal Silver – Background

Silver has been used as a medicine and preservative by many cultures throughout history The Greeks used silver vessels for water and other liquids to keep them fresh.Silver was used by the Romans to preserve water in storage jars. During war campaigns Alexander the Great boiled and stored water in silver or bronze urns to reduce waterborne disease.

Silver was used as a medicine in the late 1800’s and early 1900’s. Silver, along with other metals was discovered to possess microbicidal properties but silver alone showed both strong microbicidal properties and low or no toxicity to humans. The colloidal state proved to be the most effective form because it lacked the caustic properties of salts (such as silver nitrate) and demonstrated a high level of activity with very low concentrations (oligodynamic). In 1881 silver nitrate was first used for the prevention of gonorrhea. In 1884, the German obstetrician F. Crede administered 1% silver nitrate to the eyes of newborn infants, virtually eliminating the incidence of disease-caused blindness in newborns. When antibiotics came into widespread use in the 1930s, the use of colloidal silver was dropped.
Download full document: Colloidal Silver1.doc

MIT Thinkcycle PFP Filter Evaluation


During the last decade, several projects tackling water treatment for low-income households have likely failed due the utilization of inappropriate technology or deficient monitoring. Our team has used a system that ensures a bi-directional transfer of technology and knowledge for water purification at a household level. Through an innovative methodology design based on an iterative and real-time feedback loop, we have been able to establish solid partnership with key players in the field who have implemented a 6-month monitoring program in order to assess the performance of Potters for Peace ceramic water filters. Microbiological performance of the filter in the filter was promising but did not meet WHO targets. Survey results suggest that periodic training and constant monitoring is essential to ensure the appropriate use and successful implementation of this new technology.

Download Full Document:  MIT thinkcycle PFP filter evaluation.doc

Water for Health Declared a Human Right

Water for Health Declared a Human Right

GENEVA, Switzerland, December 4, 2002 (ENS) – Safe and secure drinking water is a human right, a United Nations committee has declared formally for the first time. “Water should be treated as a social and cultural good, and not primarily as an economic commodity,” the committee said, siding with those who object to the privatization of water supplies.
The United Nations Committee on Economic, Cultural and Social Rights took the unprecedented step of agreeing on a General Comment on water as a human right, saying, “Water is fundamental for life and health. The human right to water is indispensable for leading a healthy life in human dignity. It is a pre-requisite to the realization of all other human rights.”

General Comment is an interpretation of the provisions of the International Covenant on Economic, Social and Cultural Rights. This one was signed on November 27 as the Committee wound up its three week autumn session. Although the Covenant does not expressly refer to the word “water,” the committee determined that the right to water is “clearly implicit” in the rights contained in two sections of the Covenant. The General Comment means that the 145 countries which have ratified the Covenant “have a constant and continuing duty” to progressively ensure that everyone has access to safe and secure drinking water and sanitation facilities – equitably and without discrimination. “Countries will be required to ‘respect, protect and fulfil’ individuals’ rights to safe drinking water and sanitation,” said World Health Organization (WHO) Director-General Dr. Gro Harlem Brundtland, quoting from the General Comment.
The General Comment specifically recognizes that water, like health, is an essential element for achieving other human rights, such as the rights to adequate food and nutrition, housing and education.
“This is a major boost in efforts to achieve the Millennium Development Goals of halving the number of people without access to water and sanitation by 2015 – two pre-requisites for health,” Dr. Brundtland said. An estimated 1.1 billion of the world’s people, roughly one in six, do not have access to clean drinking water, according to WHO figures. Sanitation progress has also been slow, and some 2.4 billion people, about one in every 2.5 individuals, still do not have access to a safe latrine. Inadequate water and sanitation is “a major cause of poverty and the growing disparity between rich and poor,” WHO said. “The fact that water is now regarded as a basic human right will give all members of the Alliance an effective tool to make a real difference at country level,” said Dr. Brundtland, a physician and former Norwegian prime minister.

The Global Alliance for Vaccines and Immunization is an international coalition of partners. It includes national governments, international organizations such as the United Nations Children’s Fund, the World Health Organization, and the World Bank; philanthropic institutions, such as the Bill and Melinda Gates Children’s Vaccine Program, and the Rockefeller Foundation; the private sector, represented by the International Federation of Pharmaceutical Manufacturers Associations; as well as research and public health institutions.
The General Comment provides a tool for civil society to hold governments accountable for ensuring equitable access to water. It is intended to focus attention and activities on the poor and vulnerable, the committee says.

The General Comment states, “The human right to water entitles everyone to sufficient, affordable, physically accessible, safe and acceptable water for personal and domestic uses.”
“While those uses vary between cultures, an adequate amount of safe water is necessary to prevent death from dehydration, to reduce the risk of water related disease and to provide for consumption, cooking, personal and domestic hygienic requirements,” the text states. “The right to water contains both freedom and entitlements,” the committee states in its Comment. “The freedoms include the right to maintain access to existing water supplies necessary for the right to water; and the right to be free from interference, such as the right to be free from arbitrary disconnections or contamination of water supplies.”

Sufficient water should be obtained in a sustainable manner, the committee said, to ensure that “the right can be realized for present and future generations.”
The formal statement of water and sanitation as a human right is intended as a framework to assist governments in establishing effective policies and strategies that yield “real benefits for health and society,” WHO said. The world health agency associates 3.4 million deaths each year with inadequate water and sanitation. Diseases such as malaria, cholera, dysentery, schistosomiasis, infectious hepatitis and diarrhoea are the killers. Dr. Brundtland estimates that one third of the global burden of disease, in all age groups, can be attributed to environmental risk factors. Over 40 percent of this burden falls on children under five years of age, even though they make up only about 10 percent of the world’s population. The director-general calls this area “an urgent priority for WHO’s work.”

Zamorano Harvard Report

Household Water Filters as part of the Kitchen Improvement Project

(Cocinas Rurales)

PROMESA is a small international health program that has been working to improve the conditions in the Yeguare region of Honduras for the past four years. Currently PROMESA is working on a kitchen improvement project in four small communities (La Ciénega, Las Tablas, Las Agujas, and Rodeo) in the region. This project’s focus is to improve the health status of the families by improving the health standards in the kitchen by offering materials to improve earth stoves, install drains, sinks, install mesh on windows, and install concrete floors. One improvement that was offered to the families in the communities was a household size water filtration system to purify contaminated water. There are a variety of filtration systems; however, it was necessary to find an inexpensive, functional, and long lasting system. One filter that met those requirements was the Filtron.

The Filtron is a ceramic filter that is marketed by Potters for Peace and is one method to decontaminate water that is used for human consumption. The filter works in two ways: as a filter to remove large contaminants such as protozoa, helminthes, etc., and as a disinfectant by using colloidal silver to clean the water of potentially harmful bacteria. The silver is spread on the sides and bottom of the filter. Water passes through the pores that are formed in the manufacturing process. When the water passes through these pores it comes in contact with the colloidal silver, which acts as a bactericide. The filter is an alternative to chlorination, boiling, or using solar energy to decontaminate water (1).

Download full document:Zamorano Harvard report.doc