Here’s a Podcast I did at NCECA! Check it out if you’ve got some time.
Not exactly Oil Spots in the truest sense, these two variations were concocted and tested along with the rest of my oilspots glazes. Both of these recipes utilize some local dolomitic limestone I found and incorporated into the recipes. If you want to re-create these, using a mix of 1/2 and 1/2 Dolomite and Limestone will get you very close.
Here’s one that’s a bit of a kitchen sink: Lots of iron, manganese, cobalt, and copper.
Interesting rabbit hole on these guys can be found here: Getty.edu
Here’s my Lava Oil spot firing schedule, which always looked best fired in a neutral/oxidation atmosphere in a gas kiln.
You might notice that this one has a significant addition of Cobalt, half and half Custer (Potash) and F4 (Soda) Feldspars, calcined talc, and 2% Manganese. Typical that I changed too many things to give a really useful side-by-side comparison. But I suppose when I’m coming up with new variations, that’s always been my style.
Some observations on this one:
Cobalt goes a long way and pretty dramatically alters an oilspot. With a .25%-.5% addition you get a nice shift from brown and russet glaze matrix to a darker solid black glass. Beyond 1% you can get some really nice silvery qualities to the spots. The drawback is that the more you add, the more refractory the glaze tends to get – and the longer it takes for the glazes to heal.
“I have not failed. I’ve just found 10,000 ways that won’t work.” – Thomas A. Edison
Just spent a bit of time inputting this old recipe into Glazy.org. Pretty Sweet!