Tags:Glazing Your Pottery,ceramic ware,clay,clay mug,monkeysee,pottery,pottery tutorial,pottery wheel,sculpting,thowing clay
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Hi! I'm Jane Kelham from Manassas Clay and I'm showing you how to make a pot on the wheel.
Our bisque firing is done and now, we’re ready to glaze. It’s now cool enough that I can get my mugs and we’re going to glaze them. I'm going to glaze the mugs. But first, I want to tell you a little bit about glaze. Glaze is a suspension in water of the chemicals used to make glass. There are three major components, the first one is silica or sometimes referred to as flint or it’s powdered sand. This is the glassy part of the glaze. It has a melting temperature of about 3,100 degrees. So it is a much higher meting temperature than the firing temperature we have, so we have to add a second ingredient called the flux. This lowers the melting temperature of the silica and makes a nice shiny finish, but it won’t stick to the pot. So a third ingredient is added to make the glaze stick on the side of the pot, and that is clay.
These three ingredients make a very nice shiny clear glaze. To make a color, we add either carbonates or oxides of metals. Copper makes green, cobalt makes blue, and we can get a whole variation of colors by mixing in the oxides and carbonates. But this is also still a clear glaze. So we add a fourth ingredient called an opacifier which makes the glaze opaque.
Now, we’re going to glaze our mugs. First of all, I'm going to wax the bottom. This is a liquid wax that is an emulsion of wax and water, and you can put it on the bottom so that the glaze doesn’t stick to the bottom of the pot. This conserves glaze and you can make a very nice line. Now, I wax about a quarter of an inch between an eighth and a quarter of an inch up the side because the glaze does become molten during firing, and I don’t want it running down and attaching the pot to the kiln shelf. So after it’s waxed, it’s ready to glaze.
Now I have my glaze here, and what the pot looks like when it’s been glazed and after it’s fired is completely different. I'm going to dip it in about two thirds of the way and let it dry ‘till it is no longer shiny. There are different ways to put glaze on pots besides just dipping. You can paint glaze on, you can airbrush glaze on. This dipping puts a nice even coat and it makes for a very interesting pattering where the glaze overlaps. Now, this is dry. I'm going to dip it back in and cover the area where it didn’t get glazed and again, I'm going to let it dry. And then, I’ll take my sponge and clean that glaze off the bottom. If I left it on, it would act as glue and attach the pot to the kiln shelf.
The glazed pot doesn’t look anything now like what it will be when it’s finished. From the time it is freshly thrown to the time it’s out of the glaze firing, it shrinks almost 12%. After the freshly glazed pots are dry, you make sure the bottom is clean and then they’re ready to put into the glaze kiln. It takes about 12 hours for the glaze firing and another 12 hours for them to cool.