While mixing up test glazes, I came upon a recipe calling for G-200 Feldspar. Well, hmmm. I have Custer, a potash feldspar. I have Kona F-4, a soda feldspar. As far as I know, for our purposes, there are only potash and soda 'spars. Wrong! G-200 is 75% potash, and 25% soda feldspar. So, I should be able to achieve the same thing by substituting the appropriate proportions of Custer and Kona.
Thanks, Professor Google!
2 hours ago