Here is a short video explaining how I find variations on a glaze. You can make 39 variations in about 3 hours.

There is an error in something I said at 14:24 - 15:01. I accidently swapped the spodumene for all of the feldspar so it made the range very high. So it was not as high as 0.34 - 0.66 and the spodumene point should not be as high on the Stull chart.