Math Tips for Glaze Making

How to Make a Glaze Batch total 100%

First, why would you want to do that?

Glaze recipes/formulas are often written so that the base ingredients total 100, which means the parts represent a percent. If all glazes are written this way, it is easier to compare the ingredients if you are looking for a particular effect from certain fluxes, etc.

If a glaze base does not add up to 100, here are 2 ways to change the numbers and still keep the ingredients in the correct proportion. If your math is correct, the new total should be 100.

EXAMPLE

OLD RECIPE NEW RECIPE
Ingredient A - 85 72
Ingredient B - 16 14
Ingredient C - 12 10
Ingredient D - 5 4
TOTAL . . . 118 New Total 100

The simplest way:
Divide each ingredient amount by the total.

Ingredient A . . . . . 85 ÷ 118 = 72
Ingredient B . . . . . 16 ÷ 118 = 14. (13.5 rounded up)
Ingredient C . . . . . 12 ÷ 118 = 10.
Ingredient D . . . . . . .5 ÷ 118 = 4

If you like to use algebra:

For Ingredient A . . . . . . then repeat for each ingredient

85/118 = 1/100
118A = 85 x 100
118A = 8,500
8,500 ÷ 118 = A
72 = A

How much dry material does it take to make a 5 gallon glaze bucket of liquid glaze?

Potters often use 5 gallon buckets to hold liquid glazes they make themselves.

It's best if buckets are only 3/4 full to allow space for displacement when work is dipped into the glaze.

Here are useful facts to know.

1 pint = 1 pound "the world around"
1 gallon = 8 pounds
1 pound = 453.6 grams

How to figure:

5 gallons x 8 lbs per gal = 40 lbs

40 lbs x 3/4 full = 30 lbs liquid glaze needed.

About 1/2 the 30 lbs finished liquid glaze weight is water, so
15 lbs dry glaze is needed.

15 lbs dry glaze x 453.6 grams per lb = 6,804 grams dry glaze

If you need about 6,800 grams of dry glaze materials,
you can multiply a recipe that adds up to 100 by 60 or 70
to fill a 5 gal bucket 3/4 full.

About 6,800 grams of dry glaze materials
makes a good amount for a 5 gal bucket.

How would you compare costs of commercial glazes to those you make yourself?

1 average glaze batch is 6,800 grams / 15 pounds. Dry materials are ordered more economically in 25-40 pound bags. You will probably use the most common ones in different proportions in more than one glaze.

A 25lb bag of 4 ingredients cost $7-50 each = average $60-80 for 100 lb.
Commercially prepared dry mixes cost $50-60 per 25 lb. bag, or $200-240 per 100 lb.

If each glaze you mix is 15 lbs dry, you could get 6 buckets of liquid glaze out of 100 lbs dry mix; $60-80 ÷ 6 buckets = $10-15 per 4 gal / $3-4 per gal

Commercially prepared liquid glazes run $10-25 per pint / $80-200 per gal

Remember that cost is not the only factor to consider.
Some commercially prepared glazes may function better than ones you make yourself, or may be more consistent. However, you will still need to test the commercial glazes with your particular clay body and firing conditions.