Tuesday, June 15, 2010

Glaze Making ...

I have a glaze recipe that I worked with at the college lab a semester or two ago. It is a once fire recipe that goes to Cone 1, clear glossy.   I made up a small batch of that today for some sprig beads that I will be firing tomorrow.  Right now I'm waiting for some mugs to dry so I can bisque fire them in the big kiln. The beads, however, will be fired in the smaller kiln.

The first thing when mixing glazes is to always always wear a mask. Here's a disposable mask (N95) that works quite well. I use this type for mixing up small batches (scroll down).

The next thing I use is a gram scale, which I bought at a local ceramic's company. It also measures in ounces as well as something called 'n'. I keep thinking I ought to google that someday... someday.

Glaze recipes are written out in grams. The great thing about that is that if you want a big batch, just add a zero to the end. I was confused about the process of glaze recipes for a long time. For example, when cooking first the garlic and onions are sauteed, the meat added, some spices ... allow time to cook ... add veggies, perhaps some more spices ...allow time to cook ... etc ....

With glaze recipes, you just dump it all together, stir it up, and add in the colorants and water last ... or you can dump it into a small amount of water and add more water later. It is no wonder when looking at glaze recipes I was so confused. I was looking for "add this, stir, add that, let sit ...."   That sort of thing doesn't happen with glazes. Okay ... enough laughing. I do tend to over think some things. ha ha!

In any event, today I mixed up a cone 1 glaze.  Here's the recipe ...

CLEAR GLOSS, Cone 1, Once Fire
feldspar 3134: 61.0
kaolin : 20.5
ball clay : 18.5
add cmc : (1/2 tsp)

Feldspar is mineral composed largely of a linked chain of silica, aluminum, and oxygen elements. Along with quartz, it is the most common mineral on the continents. The word means "field crystal." It is ground up crystal that melts nicely. Kaolin is a white clay, very pure, used in porcelain and ball clay is a type of clay that is very plastic and pliable. It, along with the kaolin, will help the melted feldspar fit the clay. The CMC thickens the glaze so that I can apply it with a brush.

I could add colorants at this point, like rutile or cobalt/copper carbonate and perhaps I will end up doing that later, but right now I'm just after a nice clear glaze to coat some of the white porcelain sprig beads like the one at the beginning of this post. These will be fired at a higher temperature but the look will be about the same.

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