Characteristics for Wet Clay

[crazy.loveable.princess]

Hey everyone!

 

I'm kind of new to the art of pot making. I was wondering what the main characteristics of wet clay are. All the research that I've done on the Internet have not answered my question, so could you?

 

Thanks!

crazy.loveable.princess

[Cass]

i can think of quite a few adjectives for wet clay, but what exactly are you trying to figure out?

[crazy.loveable.princess]

i can think of quite a few adjectives for wet clay, but what exactly are you trying to figure out?

 

 

Hey thanks for replying. So what I was looking for was like what makes wet clay wet? Like for leather-hard clay, it is cold to touch, it looks like it is still wet, etc. I'm looking for characteristics like color, texture, etc.

 

Thanks,

crazy.loveable.princess

[neilestrick]

Wetness is simply a matter of how much water is in the clay. The more water there is, the softer the clay will be. Leather hard clay is firm to the touch, but still has water in it. When it is totally dry we call that 'bone dry'. Most moist clay (clay that we make pots and such with) contains somewhere around 15-20% water by weight. When you add a lot of water you get slip (liquid clay).

 

The clays that we use are actually what we call 'clay bodies'. They are a mixture or different types of clays plus silica, binders like feldpars, and textural materials like sand and grog (ground up fire bricks). Each company that mixes and sells clay bodies have their own proprietary formulas/recipes. And just like there are a million ways to make a chocolate chip cookie, there are a million ways to make a brown cone 10 stoneware.

 

Clay bodies are selected based on 3 primary criteria: firing range, color and texture.

1. Firing range: Clay bodies typically fall into 3 firing ranges- low fire (cone 08-03), mid range (cone 4-6) or high fire (cone 9-11). Your clay and glazes should always mature at the same cone.

2. Color- Typically determined by how much iron is present in the clay, as well as firing atmosphere.

3. Texture- Can be really smooth, really rough or anything in between. Clay companies often mix 2 or 3 versions of the same clay body, just with different levels of grit/texture/roughness.

 

Hope this helps.

[Marcia Selsor]

More characteristics include plasticity. not all clays are the same even wet. If you roll a little coil out and twist it into a pig's tail spiral, some clays will break and others will bend easily. That is a plasticity test. Finer particle clays tend to be more plastic. Gritty clays with lots of grog are not plastic.

marcia

[yedrow]

I'll approach it from a little different perspective, not necessarily to add anything, but to give a different view. At first the clay is the wet clay you buy and throw with (unless you are mixing you own). This varies in consistency from mushy and easy to push your fingers into, to stiff and somewhat resistant. Wet clay is easy to center and work with at first, but later on in the making of a pot it becomes difficult because it 'flows' or twists under your hands. Stiffer clay is more difficult to center, but is easier to work with later on in the throwing. This is the clay you throw with.

 

After that it is drying to the point of "leather hard." Nothing happens here, it just dries

 

The clay is leather hard when it gets a consistency somewhat like that of a block of cheddar cheese. It will bend some, but will soon crack or develop cracks. Experience will teach you when it is best to trim work in the leather hard stage. If you start too early you risk deforming your work and digging into it, both by loosing control of the line your tool is making, or by going too deep into the wall. If you trim too late you will have to work harder and worse, you will leave little tears in the clay that could develop into cracks during drying or firing. When the clay is just right the trimmings will hold together well and curl up under your tool like cold butter. Leather hard is the trimming stage.

 

After that the clay is drying to the point of being bone dry. As it dries it will lose its color and the evaporating moisture will make it cool to the touch. If you have questions about a pot, pick it up and touch the bottom. If it is cool it is probably better to let it wait a day or two more, especially if you have thick walls, and if you are new you will.

 

Bone dry is when all of the water is out of the pot [except chemical water]. This is the stage when the clay is ready to be bisque fired.

 

Incidentally, there are four types of water in clay, surface water (the shiny stuff), pore water (the stuff between the particles of clay), bound water (the stuff attached to the particle of clay), and chemical water (the stuff in the molecule Al2O3 2SiO2 2H2O).

 

Joel.