I finally have been able to make a hard, durable brick. I was lacking a flux that would work in the short firing time frames I am forced to use. Salt and lime didn't work fast enough. But ground up glass dust did. What takes pure clay several days firing to do, I now can do in 1 day!
Old scrap glass from bottles, windows, and television picture tubes is smashed down in my mixer with heavy round stones.
Then I sift the crushed glass down to remove all large pieces
Old scrap glass from bottles, windows, and television picture tubes is smashed down in my mixer with heavy round stones.
Then I sift the crushed glass down to remove all large pieces
before adding it to the clay to press out bricks.
I am using a 50/50 mix of clay and glass.
Then I fire the bricks same as before.
Then I fire the bricks same as before.
The three bricks to the left are regular clay bodies for a control. The forth, sixth, and seventh are 50/50 red field clay and glass. The fifth brick is 50/50 grey streambed clay and glass.
The controls were not vitrified and crumbled easily. The red clay/ glass bricks were solid and passed water absorbtion testing averaging 11% and maintained full strength. The grey streambed clay / glass brick had absorbtion at 22% and split minutes after submersion in a bucket of water.
I attribute the failure of the streambed clay brick to the high level of lime pebbles in the clay mix it was made of. The lime swells as it absorbs water causing fractures in the clay body of the brick. I will work on removing the lime pebbles for the next tests as I really liked the near white look of that brick and would want some of them to hold up for me.
Hello Richard,
ReplyDeleteThank you so much for your comment on my blog, it has been a real joy to hop across to your blog as a result of that, and to discover what you have been up to. I am really impressed with your kilns and furnesses. The aluminum smelter was delightful, with the nice brickwork around the fire place and the round chimney. As a potter, I also had the thought that it might make a raku kiln with very little modification.
I am interested with your brick making, and the tests that you have made with your local clay and various fluxes. The use of waste glass as a flux was great, and looks like it will work out well. I am assuming that your local clay must be quite refractory, possibly a fireclay. I think that our clay here, which is earthenware, would fuse together quite readily at the temperatures you are firing to without the need of an extra flux. It would be interesting to be able to fire a sample of your clay to stoneware temperatures (maybe in a local school kiln??) and see how it performed. It would also be interesting to place a few pyrometric cones in your kiln to see what temperature you were acheiving. The red cones are badly affected by reduction atmosphere in a kiln (as the iron oxide in them turns into a flux under reduction), so if you do try some, do use the non iron bearing Orton cones if you can get them. (I would be tempted to set cone 07, 05, and 03 in your kiln as a starting point.)
I would like to put a link to your site from mine if that is OK with you.
Best Wishes, Peter
Yes Peter you may put a link up. Good to read of your interest in my experiments with natural clays. I will look into getting some cones like you recommended to try and identify my temperatures in the kiln better. Very useful information, thank you. I have since fired the kiln again and had improved outcomes on my red bricks. I will post some of the results in a new entry. Look foward to chatting again,
ReplyDeleteRichard