Note: This article is from Jesse Wiseman Hull’s website, now archived here.

Monday, January 28th, 2008

A glaze recipe is almost always listed as a “percentage or batch formula”, adding up to 100. Every once in a while you’ll run across something that is slightly off (I was shown one adding up to 98.63% recently) -but that’s uncommon.

As stated in my post “Getting Started with Crystalline Glazes“, when people ask me for a crystalline glaze recipe (^9-10), I offer them this to start with:

Frit 3110: **50** %

Zinc Oxide: **25** %

Silica: **25** %

**50** + **25** + **25** = **100** %

The above would technically be referred to as a *percentage formula* . If you wanted to make a small test, you’d probably just want to mix up 100 grams.

This would then be called a 100 gram *batch formula* :

Frit 3110: **50** grams +

Zinc Oxide: **25** grams +

Silica: **25** grams

= **100** grams

Ok, so say you find that the glaze works, and you want to mix up 600 grams to test further…

Look at the above formula again, like this:

Frit 3110: 50 (x 1) = **50**

Zinc Oxide: 25 (x 1) = **25**

Silica: 25 (x 1) = **25**

= **100** , right?

So for **600** grams:

Frit 3110: 50 (x 6) = **300** +

Zinc Oxide: 25 (x 6) = **150** +

Silica: 25 (x 6) = **150**

= **600** grams

For **800** grams, multiply each part by **8** ,

for **950** grams, multiply each part by **9.5** ,

and for **1000** grams, multiply by **10** .

In John Britt’s book “Complete Guide to High Fire Glazes”, I list an *Alkaline Base* Recipe:

Frit 3110: **51**

Calcined Zinc Oxide: **23**

Silica: **22**

Grolleg Kaolin: **2.5**

Alumina Hydrate: **1.5**

= **100** %

The above formula is called a *base glaze* . Base glazes typically come out clear or white. To this you can add colorants, modifiers, binders, etc. These are *not* usually listed as part of the formula, but you’d still multiply each one by the same number, to get an equal proportion in the glaze.

For **750** grams…

Frit 3110: 51 (x 7.5) = **382.5** grams

Calcined Zinc Oxide: 23 (x 7.5) = **172.5** grams

Silica: 22 (x 7.5) = **165** grams

Grolleg Kaolin: 2.5 (x 7.5) = **18.75** grams

Alumina Hydrate: 1.5 (x 7.5) = **11.25** grams

To get the dark blue glaze pictured on pg. 137 of Britt’s book, add:

Cobalt Oxide: 3 (x 7.5) = **22.5** grams

Manganese Dioxide: 3 (x 7.5) = **22.5** grams

Red Iron Oxide: 3 (x 7.5) = **22.5** grams

Bentonite (or CMC as a binder): 1 (x 7.5) = **7.5** grams

So you have **750** grams of the base + **75** grams of colorant and binder = **825** grams.

Now you can use that result to calculate how much water to add.