Clay processing

[Mullins Pottery]

Hello all,

As is happens I live in a desert. All the local earthenware clay I dig up is already dry and mostly free of impurities. Much of the research I've done regarding the processing of clay suggests that after drying the clay one should break up the dry bits into pieces then screen dry then re-hydrate to appropriate consistency. In my process I basically use the blunging process instead of dry screening. Aside from the drying process taking a couple days I cant think of anything that makes this process less viable. I've found this to be quite effective in weeding out the impurities. I'm wondering if there's anything wrong with doing a wet screening as opposed to a dry screening. Any thoughts?

My process is this:

1. Dig up clay

2. Re-hydrate clay

3. Blunge into slurry

4. Pour through screen mesh twice

5. Dry to appropriate consistency on drying table

6. Wedge into logs

8. Bag & age

[Mark C.]

Just as long as you do mind mind dealing with impurities in the wet stage.You may be getting a few organics that hydrate in the wet stage and pass thru the screen. The bottom line is -is the clay turning out ok for your end use???

[Mullins Pottery]

Thanks for the reply Mark. I'm basically just trying to cover all my bases. I hadn't considered the possibility of re-hydrating organics. Thankfully I haven't found any in the clay that I've worked with so far. This clay has been pretty awesome. Great to throw with or handbuild. It dries very nicely for durable workable greenware and fires beautifully at cone 04. I just haven't seen much being said about processing this way and am wanting to avoid any possible pitfalls. 

[Magnolia Mud Research]

The answer to you question resides in the characteristics of what remains on the screen after completing step 4.  If the "lumps" being retained on the screen seem to be stuff that belongs in the final moist clay, crushing them dry MIGHT, but not necessarily will, be the right thing to do.  You can also crush these wet lumps and add the slurry back to the main batch. 

Crushing dry clay is dusty, and requires equipment to do so.  I gather clay from my pond bottoms when they dry out.  Crushing is only done to facilitate storage.  However, small particles blunge more easily than big lumps.  Its a tradeoff. 

I concur with Mark's remarks. 

LT 
 

[Mullins Pottery]

Thanks Magnolia another thing I haven’t considered. I do end up with some left over inorganic material but I’m not sure what it is. It acts similar to clay but it refuses to break down and further with my mixer. I can smush it if I smear it across my hand but even when I place all of this material in a bucket with like 200% water to try to break it down with my mixer it refuses. I’ve fired it both with and without the extra material and I have not noticed and difference. However when I exclude the extra material the clay body is easier to throw. I’ve been wanting to send a sample to a lab to figure out exactly what the material is composed of but have yet to do so.

[PSC]

If the source is really clean screening may not be a problem. Back in college with more time than money i dug my clay from a known pit that area potters had been digging for generations. The clay was very pure coming out of the pit. I'd just hammer it into lumps,  add water to make a slurry, pour off the excess water, and throw it in the clay mixer with a little ball and fire clay and some dry 182 that i ordered from stardard and it made a great throwing clay no screening needed. Now occassionally there would be an iron pyrite in the clay that you would find as you brought up a wall or the kiln would find it and give you an interesting burnout down the side of your pot. Not often enough to make me want to spend time screening tho.