Glazes make up one of the most important part in the pottery making process. A finishing touch on the canvas you have just made with clay, and a protector against its daily toils as a functional pot. Glazes have as many different characteristics as do the people who make them; they can be glossy, matt, transparent or crystalline. They can also run, pool, break, drip, crackle, craze, and layer; the possibilities are endless! A lot of folks enjoy shopping for their glaze, picking up a tried and true bottle, of their favorite Amaco’s Potter’s Choice Chun Pum, or one of Mayco’s Stoke and Coat line. While some people, enjoy the challenge of creating something completely their own. These folks, roll up their sleeves and take off the potter’s hat, and don the Chemist’s lab coat (and respirator!). Making your own glazes can seem like a step out into the unknown, and with the numerous recipes available online, who can decide which one to pick, or how even to read the formula? If you’re itching to try your own recipe but don’t know quite where to start, I’d like to offer this simple “how to” in order to demystify the process and help you feel a little more comfortable breaking out the scales. For this installment, we will just cover how to read the recipe itself.
Things you’ll need:
- A recipe!
- A calculator
If you do a quick internet search, you will find a plethora of glaze recipes, but finding out which ones are reliable is another matter. After much research, I believe that Tony Hansen’s online database, Www.Digitalfire.com is the most reliable, comprehensive, and informative glaze website. If you have awhile to study the in depths of glazes, this is a great place to start. On Tony’s site, he has a number of “starter glazes”, or glazes that offer a good foundation on which to begin study and experimentation. For our purposes we will use the famous “5×20” glaze.
The name 5×20 comes from the 5 different oxides in the glaze, and each oxide takes up 20% of the whole recipe. This glaze was developed because of its simplicity, and because of how well it works with stains, and the above recipe will form a very glossy, hard, transparent clear glaze.
You see here the classic glaze recipe. Each recipe consists of multiple naturally occurring raw materials which are made up of different oxides that have properties needed to form a glaze. In different proportions these are mixed together to get a desired effect.
To make things easy on the glaze maker, who may want to make a large or small batch, each recipe is based on percentages.
For example, each “20” listed above means 20% of the whole of the glaze, so the glaze maker will just need to determine how much glaze they would like to make and then break it down by percentages to determine how much raw materials to weigh out. All of the materials together should add up to be 100% of the glaze.
Let’s assume you want to begin with a small batch just to test this glaze out and see how it works with your clay and you decide 1000 grams is a good starting point.
1000 grams is then going to be your overall weight for all the raw materials listed in the glaze recipe. Now we will break down the weight of each material.
If each ingredient in the glaze takes up 20% of the 1000 gram glaze, then all we have to do is multiply .20×1000 to find out the weight of each ingredient. Wollastonite at 20% of 1000 would be 200 grams, and too Frit 3134 would also be 200 grams and so on throughout the recipe. That’s it! A simple as that! Some recipes will have more precise percentages, but the process is the same no matter if you want 100 grams, or 10,000 grams of glaze.
Now that you have all of your weights, you may be wondering how to order your materials. For all us ‘Muricans, most stores sell in pounds, so you’ll need to just a little more math to figure out how much to order. There are 454.59 grams per US pound. It is wise to always order a little extra than you may need in case of mishaps. So what we do now, is divide 200 grams by 453.59 grams to determine how many pounds it weighs. 200/453.59=0.4409 lbs or just under 1/2 a lb. There you go! Glaze recipes do not need to be confusing, but rather very simple.
One thing to note, in most recipes there will be additions after the 100% base recipe. These are normally colorants or glaze modifiers and can be added the exact same way as the other materials. I hope this brief explanation helped understand the basics of reading a glaze formula and gets you on the way to creating your own beautiful and custom pieces of art.