Sabaidi!

There are a number of factors to consider when producing this variety of clay pot water filter. Please allow me to talk a little about these factors and illustrate some of the aspects we must consider when designing a working filter.

Thickness of filter: This is a crucial factor as there is a trade-off between a thick filter, which will remove more bacteria, but at a very slow flow rate; and a thinner filter that traps fewer bacteria, but allows water to flow faster.

Firing the filter: The thicker a filter is the more difficult it is to fire. Thicker filters must be sun-dried for at least a week before they can be fired. This is to remove all the moisture from the wet clay. Water causes the clay to crack, or even more spectacularly – explode, during firing

Clay-to-coffee ratios: Tony Flynn has found that an approximate 50/50 ratio of coffee-to-clay is good, but that 40/60 and 60/40 combinations have also proven effective. We need to experiment to find the optimal ratio.

Coffee grounds: The coffee grounds in Laos are coarser than those found in Australia. We need to experiment with locally available methods to grind them finer. Ultimately, we are seeking to replace coffee with something that is even more widely available. One step at a time though, we’ll use coffee as that has already been demonstrated to work.

Type of clay: The Lao potting techniques have a few unique characteristics, namely that pottery is fired using rice straw and without a kiln. Pieces are exposed directly to the naked flame, thus experiencing a rapid rise in temperature. The temperature climbs much faster than during a kiln firing. To alleviate the effects of thermal shock, a special mix of pre-fired clay is mixed with the wet clay used to make pieces of pottery. When done by a skilled potter, adding this pre-fired clay, allows the pieces to undergo rapid temperature changes without cracking or exploding.

Adding pre-fired clay may alter the filtration properties of the filters. We will investigate the possibility of producing a filter without pre fired clay. Also, we will determine the impact of pre fired clay on filtration rate, effectiveness, and taste of the filtered water. Steps will be taken to explore methods to reduce any negative impacts the pre fired clay has on the filter characteristics.

Density of the filter: Our discussions with Tony Flynn indicated that the density of the filter is very important in ensuring it functions correctly, as a filter that is too dense will not allow water to pass through. In Laos, pottery pieces are shaped by placing the piece on a wooden anvil and beating it with a paddle. This compacts the pots and may require adaptation to produce a low density filter.

Our approach in effectively implementing the use of these filters in rural Laos and ensuring potable water has a few stages: Firstly, we will experiment with the pottery process and materials to create a filter that reliably removes bacteria. Once we have a working filter we will adjust various aspects to meet the needs of users, such as size, shape, durability and flow rates. Finally, we will simplify and standardise the production process, while seeking to make it as universally applicable as possible. We will also investigate potential alternative materials.