I have finally finished one research assignment (which I will be posting details of very soon) so before I start the next very huge research assignment for my ceramic history class, I thought I would take a breath and catch up on all the post I have been wanting to do and have had no time for.
So here goes, this one is from at least a month ago. As part of my glaze class we were to find clay in our local area and test it. We were told that good places to find clay are the curves of stream and rivers where the clay has been deposited after traveling all the way down from higher ground and become secondary (terracotta) type clay. And since I live in the valley in Mountain ranges, I am in a perfect spot to go find some clay, and I did. Just across the road in fact, there is a stream called sassafras creek where I collected some clay from the creek bank.
As well as finding clay, I found pretty little pictures everywhere.
Then I drove down the road to where I had seen bright red clay on the side of the road. We had just had a huge down pour of rain and it had washed clean the clay that lines the drainage next to the street. Perfect.
I bagged up all my collections and also ended up collecting clay from the park down the road that was an amazing bright red colour and this is what I ended up testing. We did minimal processing of the clay that was to be tested, just pulled out the sticks and rocks in the clay, then mixed it up with a little water into a thick cake mixture type consistency and left it on a cloth and newspaper to dry out a bit. This made sure the clay was all combined and stuck together in order for us to cut it into bars to test, with out it all crumbling apart. After if was dried to a soft leather hard, it was cut into bars. We were testing the shrinkage, by marking out a 10 cm mark on the bars at the wet, soft leather hard stage. Then these were to be measured after bisque firing to 1000 degrees celsius, and then again after being fired to stoneware approx. 1280 degrees celsius. Because this is a terra-cotta type clay that doesn’t usually withstand stoneware temperatures and could melt and fuse to the kiln shelf, the bars need to be placed on another piece of scrap stoneware clay to protect the shelves. We also weighed the bars at these stages. Hopefully if the clay fires nicely, I might start using it for some special MOUNTAIN pottery products. Straight from nature, there isn’t anything better.
I will post the results of the firing and test shortly, keep a look out.