Clay Pottery Process
what makes pottery aquarium safe?
What makes pottery aquarium safe? How do I know if two different types of clays can be blended together?
I am in the process of starting up a small business. I make aquarium ornaments and other decorative pieces out of earthenware. I want to add some color to my work without glaze. I'm considering using two or more types of clay in a single piece. How do i know if two clays can be blended into a single piece? I know it has something to do with the shrinkage rates and grog %. But where do I get this information and exactly how close do two types of clay have to be to be workable together. Also how do I know if a particular clay is aquarium safe. The supplier came right out and told me the first type of clay I used was safe but they aren't being nearly as helpful now for some reason. How do I know if the clay will hold up in water? How do I know if it will affect water chemistry?
As far as I know you can always ad pigments into your clay to get the look you want without mixing two different clay types. Most clays will mix fine but you will have to do a full mix and not layered or ribboned if the grit is too different in size from one another. You can test to see by doing a double layer peice and firing it and then water testing it to see what happens. If it comes all apart then the clays are too different without full mixing.
And as long as your peices are fired you won't have any problems with the water. (Been there done that!) If you don't plan on using glaze then firing should take out any harmful chemicals that might be in the clay. (If you use glaze use a non-leaded type) You can also test this if you really want by making a few peices and adding fish from Wal-Mart.
Hope this helps! 
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