Ingredient Amount
Gerstley Borate 26.00
Nepheline Syenite 48.00
Edgar Plastic Kaolin 6.00
Silica (325 mesh) 20.00
Add Amount
Cobalt Oxide 1.00
Light Rutile 4.00
Spanish Red Iron Oxide 2.00


This is the "original" or perhaps more accurately "typical" Floating Blue recipe. The mottling and streaking in the floating effect is produced by the combination of rutile and boron in the glaze.

Published in "Substitutions for Gerstley Borate" by Jeff Zamek, in the Oct 2001 issue of Ceramics Monthly.
One thing to note about Gerstley borate is that is has a tendency to gel in the bucket over time. This can affect application, so it may be best to mix a large batch dry, thoroughly mix it, and then wet-mix only what you'll need at a given time. If it gels, and you mix more water in to thin it out, you'll be applying less actual glaze material with each dip, for example.