Water and clay

I was reading somewhere the other day about water and throwing. The article was about the notion that too much water is bad for the walls of a pot and weakens it. I immediately began thinking about the various "wives tales" that seem to survive generation to generation without skepticism. This is one. Flat out- you can not use too much water when throwing. But that statement makes one important assumption, that you are using good technique.

The explanation goes like this- the walls of a pot are built as a result of compression or pinching the clay between the fingers or any other relatively narrow point of the hand (I have known potters to use the knuckle or thumb, for instance). This means the compression points must be directly opposed. You can't have compression any other way. In doing this, you assure the wall is as strong as possible (tight) and as such, it just cannot take in water. I suppose you might be forcing a bit of h2o into the surface of the wall in any given pull. But you are also clearing the wall of water as you bring your fingers up (the pull). The wall is always dryer beneath the pull. The key is compression (we will make the distinction between a compression pull and a shaping pull in a later post).

Here is how wall weakness begins- if you lose compression you are stretching (tearing) the wall (in tension) which is literally opening the wall to water penetration. You lose compression by letting the inside contact point migrate above or below the outside. The wall is weakened from the stretching. Water will exacerbate this weakening, but it is not the culprit.

The second important point is that water is used to lubricate. And slippy water is a better lubricant (to a point) than fresh water. So always add water to your water bucket rather than starting over with fresh tap water. Throwing slip is high(er) in solids which do not penetrate the surface of the wall (in fact they align parallel to the wall, which helps lubrication). As the throwing slip loses its ability to "sheet" the wall, add fresh water to it.

Clay is often used to protect surfaces like a cellar wall from exposure to surrounding ground water. The clay is compacted in and around the basement. But another test is easier to carry out. All potters learn very quickly that dry clay sucks up water very fast. Remember the pot that got to dry to trim? Putting green ware in water will leave you with a dissolved wall inside of five minutes if not sooner. Do the same thing with leather hard ware and you find the time it takes to soften is longer. Water moves through clay by capillary action. But you need capillaries. The denser the clay (wet and well wedged) the smaller the capillaries.

So the problem is not directly the water, but losing compression on any given pull. This happens when the fingers are not directly opposed, creating a tension or stretching of the wall as it is "folded" through the fingers. This allows water to infiltrate the wall and the wall to weaken. From a teaching standpoint, the rule is still to use plenty of water. Learning to throw is tough enough without having to fight the drag that dry throwing creates.

Finally, to throw without water is no doubt a virtuoso performance. But I can't help but feel the walls straining between my fingers, torquing at a greater rate than lubed clay and being stretched unmercifully. Having said that, I still am amazed at the skill some possess. I remember the great California potter, Michael Frimkiss demonstrating his dry technique many years ago at Supermud at Penn State. What a touch. But I think he could do it wet as well as he could dry.

Add to this discussion, please. I know there are other variables like grog content and plastic clay content, form, shape and wall structure. The order of wall construction (top/down, axis/out) is another topic very much related to this. Would love to hear them.