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Re: native pottery part 2

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iowabow:
I think that adding water was not the simple process but rather a faster process to reduce the shell  to powder. If you just place a burnt shell on a table it will reduce to powder by taking up co2 from the air. This process requires a long time. I figure that if I lived in a fire heated lodge this process would be accelerated. Using water will accelerated the breaking of the shell but it will still need to be dried and CO2 will still need to be taken up. I am still not sure which will be faster. I do know that the water process is more human energy consuming. I have worked out a plan to remove the processed lime. I will stir and pour off the lime material leaving the heavy stuff that did not reduce. This bucket will settle and the water poured back and the process repeated till all reduced material is removed.

iowabow:
With rain coming I changed plans and poured off the fine particles this morning. The heavy material measured three inches in a 5gal bucket. I feel real good about the burn and should have the amount needed to produce the clay in a few days. The clay will take about two week to be ready. So now I will wait and pour off water as it comes to the top in with both clay and lime.

iowabow:
Its a good time to remind folks why the calcium carbonate is added to the clay. It will reduce shrinkage during the making of a pot and this helps prevent cracks that form during drying and this material  acts as a thermal shock absorber reducing the occurrence of cracks during firing. 

sadiejane:
all of the pottery sherds i have found along the missouri river and attributed to the ioway in woodland(iirc) times
have very distinct and visible shell fragments as seen in this piece.

until your post i didnt realize they heated the shell. tho i did understand why they used it.
really am enjoying this post and plan on using yr gathered knowledge to produce some primitive pottery.
thanks!

iowabow:
We should have pottery that looks very similar to the example you posted. The particles in many cases are as follows; very small, the size of sand and maybe a little larger. There was a really good paper I read about a site that was excavated and unfired clay was found. They could tell that the shells had been cooked before it was added to the clay. If you take a shell and hammer it into dust you will spend hours getting it processed (you will have the same product as my process). Using the heat and reducing using a dry method (air) or a wet method (water) should produce the same product...calcium carbonate.

In my process I  kept the heavy material to examine more closely for particle size and so I can compare it to  the lime particles. The picture you posted really seems to support the prefire idea because the particles look very fine and seem more rounded than the pottery I made by crushing the shell rather than burning it for reduction. My first pots had shard like particles because of the hammering. Your photo is great because you can calculate the percent based on the color change (some what), this supports the 20% idea of clay to shell.
I have really expended very little energy in producing the lime and much less than I thought I would with the filtration process.

Filtering the lime...I mixed the shell in a wheel barrel with water (4 gals) and poured off the suspension of material in to a 5 gal bucket located at the right front of the wheel barrel. I then added more water to the mix (about 2 gal) then mixed and poured the contents into an other bucket. I did this one more time with 1.5 gals of water and this was very clear by this point.

Settling the solution.. I went into the house ate and took a shower by the time I returned the lime and the water had separated....then I poured the water off and into the bucket of undissolved shells so I could save it till later. I then combined the two buckets of lime and set it off in a sheltered area.

notes.. I saw a scum on the surface of the water before pouring the water off.. I guessed that it was the surface lime reacting with the air and taking up CO2. These sheet that looked like sheets of ice were poured off with the water as well as minor contaminants floating on the surface, grass, small pieces of burnt wood, and other unidentifiable particles.  Surprisingly I now have what appears to be a rather clean sample of calcium carbonate in a quantity that is useable and required very little work other than the thinking part about what would be the most simple and primitive method of mass production.  This would have been very easy to do during this time period. The only modern equipment were the containers, a rake, and tongs. All of which can be substituted for containers of that time period. I just don't have the village of materials to draw on to demonstrate this with primitive tools. I will however when I start firing this pottery! hehe

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