As a simple base line; start with: 25% native clay, 20% silica, and 55% Nep SY. (8.58 total alkali - molar)
The color is very nice. You could use Nerd's suggestion but do a test in increments of 5% of the silica and Neph Sy.
Begin with 5 silica and 10 NS and increase. You may have to test again to get the right ratio, Texture is determine by the ratio between the silica and the clay.
The best answer is probably "try it and see"... but would doing the same with Custer Feldspar, instead of NS, be an option worth trying ? (I already have some Custer on-hand, and would have to go buy some NS to try it.)
- D.M.Ernst likes this