Copper Red Biaxial

Attempting a Copper Red with "normal" flux ratio of R2O:RO 0.3:0.7. (Most formulas I've seen have higher R2O levels of 0.4:0.6 or more.) Fixed 0.15 B2O, 0.02 SnO2, 0.01 CuO (1% Tin Oxide and 0.35% Copper Carbonate). Fired together to Orton Cone 10 in reduction starting at cone 010 with 30-minute oxidation hold at peak temp. 
This time I'm labeling the X-axis with SiO2:Al2O3 instead of SiO2.  Using the silica:alumina ratio as the axis seems clearer to me.  The Si:Al ratios are 7, 8, 9, 10, and 11.