Miracle of miracles - finally got a full day in the studio - started late morning and went back after dinner and worked till 8 o'clock. I got a lot of various things done - threw a couple of items, trimmed test tiles, sorted three bowls of test tiles; and pulled the one with the slips I want to re-test with a light amber glaze over, as well as a couple of honey and amber test tiles. Then I got the old test batches out to reconstitute today, got a stoneware buff clay ground down, mixed and sieved to test as a yellowish tan slip, made push handles for one of the texture slabs that I missed, and a lot of cleanup to boot!
Going through the various test tiles I found a nice deep caramel glaze using 10% Turkish Burnt umber that I've had for years. Unfortunately, I only have a tiny bit left and no one seems to sell Turkish Burn umber unless I want to order a 50 lb bag from India. I'll keep searching but so far, no luck.
I like the glaze a lot, other than some tiny black specks, but I'll re-sieve it in a 200 mesh sieve and see if that makes a difference. I also want to weight out another test batch with the other burnt umber I have on hand which is a totally different color than the Turkish, which is a deep rich, reddish brown, as opposed to the greyish colored regular burnt umber. I can't imagine that the currently available material would give me that rich color; but all will be revealed when I can get around to testing it.
This morning I back engineered the material to get a recipe to see if I could make my own Burnt umber in a pinch; but realized immediately that it would be a waste of time and energy.. If the greyish one is weaker, I can only add a bit more iron to get the right color. Burnt Umber is basically a mixture of iron oxide, some manganese with small amounts of calcium, magnesium alumina and silica. Come to think of it, I can probably just add 5.39 red iron and 1.15 % manganese carb since those represent how much I would get if I added 10% burnt umber. One more test added to the "to do" list for another day. Today is going to be dedicated to dealing with reconstituting those colored slips, getting them mixed and sieved and on to test tiles.
Time to stop multi-tasking and get back to eating my oatmeal after I remove the blob that just fell on my shirt!