local clays

I use a lot of local clay and am will probably write about it lot...

I live in a really clay rich area on the eastern shore of Mobile Bay.  There are so many exposed deposits of usable clay that really need little more than wedging to be a passable working body. In the 1800's there were dozens of kilns dotting the beaches and bluffs along the wooded shore where the clay banks tumbled into the water and were cut cleanly by spring fed streams. 

There are quite a few different working and firing qualities to our local clay, but the one common thread is that they are all unusually high in silica.  This is normally not a problem and most clays do really well without any additives.  However, I have run into problems with spalling and dunting with one very tight and white clay (with ocher and rosy iron marbling) from a west mobile mine.  I now add about 10 percent felspar and a little ball clay to most of the local clays to help bring some of that cristobalite into a less dangerous form of silica.