OK I have to preface this recipe with a bit about my kiln. I have a little second hand kiln in my basement studio that I love. Its quite quirky like me and yet very reliable. I fire most of my glazes to Cone 6-7 but my kiln fires so fast that I get quite different results from most other kilns. That said, make sure that you test any of my recipes and feel free to tweak the colorants.
Base Gerstley Borate 44%
Add Copper 5%
Cobalt 3% or a bit more for a darker color
Its my easiest glaze to create because there are so few base ingredients. I'll have to post a pic of me with my mask on next time I mix glazes.