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The one drawback of getting help with glazing the pots is that we don't always notice there's a problem.
Take my green glaze, for instance. I don't use it often, mostly for dragons and dinosaur banks, so I don't always remember that it settles horribly fast. If you don't mix it every few dips, the bulk of the glaze minerals settle into concrete on the bottom of the bucket, leaving just enough in suspension to fool you into thinking everything is fine.* Everything isn't fine.
So Denise glazed fifteen St. Vincent de Paul bowls in what turned out to be an extremely thin coat of green, which came out of the kiln horribly dry and brown.
Under normal circumstances, that'd be it. Gone for the shard pile, or a seconds sale. Glaze only sticks to pots when they're porous; the water is soaked up by the bisque, leaving a coat of glaze on the surface to dry. With already fired pots, the glaze runs off the surface before it has a chance to dry.
Unless.
Some time ago, I had a kiln failure. My bisque kiln didn't shut off on time, kiln sitter jammed, and by the time the cone melted away entirely, the whole load had hit cone five or six. Vitreous, non-porous, not glazeable. Most of it went in the dumpster, but I set aside a bunch of bowls for an experiment.
Thoroughly mix a bucket of glaze. (I used Cookie Monster Blue.) Next to it, on your work surface, set a big clean-up sponge, wet. Stack the pots in a small electric test kiln set on high and preheat for, oh, half an hour. Being careful not to touch the hot brick (or glowing elements), fish out one pot at a time using glazing tongs. Dip in the glaze, which will hiss and boil horribly. Bring out, wait to dry, and dip again. Wipe the bottom of the bowl off on the sponge, then set aside to cool. Continue until you've glazed all your pots, then preheat the next batch. When cool enough to handle, do a more thorough job cleaning up the feet on all your bowls. Fire to cone 10 and donate to Empty Bowls.
You have to use a fairly forgiving glaze, one that'll flow enough to fill bubbles and boils. The second dip will help, but the surface will never be smooth enough to paint/decorate. Hence the donation to Food for Lane County.
These bowls would be re-fires, so I don't want them to go all the way to cone 10, cone 9 is hot enough. Since the green glaze isn't sensitive to oxidation/reduction, I can refire them in my electric kiln at home. I also preheated them in it, programmed the computer to heat up to 450° F. and hold there. (I tried 250°, but it wasn't hot enough to boil off the water before the glaze ran off.) I had one bowl develop cracks from the thermal shock, and a couple that didn't take on enough glaze, but out of 15 bowls, 12 were good to go in the firsts box.
On the left, you can see what the bowls looked like coming out of their first firing, and what they look like after the glaze dip. On right, after the firing.
*(My white glaze also likes to do this, which is why I mix a generous teaspoon of epsom salts into each bucket. Apparently I should have done likewise the last time I mixed up Dragon Green.)
Take my green glaze, for instance. I don't use it often, mostly for dragons and dinosaur banks, so I don't always remember that it settles horribly fast. If you don't mix it every few dips, the bulk of the glaze minerals settle into concrete on the bottom of the bucket, leaving just enough in suspension to fool you into thinking everything is fine.* Everything isn't fine.
So Denise glazed fifteen St. Vincent de Paul bowls in what turned out to be an extremely thin coat of green, which came out of the kiln horribly dry and brown.
Under normal circumstances, that'd be it. Gone for the shard pile, or a seconds sale. Glaze only sticks to pots when they're porous; the water is soaked up by the bisque, leaving a coat of glaze on the surface to dry. With already fired pots, the glaze runs off the surface before it has a chance to dry.
Unless.
Some time ago, I had a kiln failure. My bisque kiln didn't shut off on time, kiln sitter jammed, and by the time the cone melted away entirely, the whole load had hit cone five or six. Vitreous, non-porous, not glazeable. Most of it went in the dumpster, but I set aside a bunch of bowls for an experiment.
Thoroughly mix a bucket of glaze. (I used Cookie Monster Blue.) Next to it, on your work surface, set a big clean-up sponge, wet. Stack the pots in a small electric test kiln set on high and preheat for, oh, half an hour. Being careful not to touch the hot brick (or glowing elements), fish out one pot at a time using glazing tongs. Dip in the glaze, which will hiss and boil horribly. Bring out, wait to dry, and dip again. Wipe the bottom of the bowl off on the sponge, then set aside to cool. Continue until you've glazed all your pots, then preheat the next batch. When cool enough to handle, do a more thorough job cleaning up the feet on all your bowls. Fire to cone 10 and donate to Empty Bowls.
You have to use a fairly forgiving glaze, one that'll flow enough to fill bubbles and boils. The second dip will help, but the surface will never be smooth enough to paint/decorate. Hence the donation to Food for Lane County.
These bowls would be re-fires, so I don't want them to go all the way to cone 10, cone 9 is hot enough. Since the green glaze isn't sensitive to oxidation/reduction, I can refire them in my electric kiln at home. I also preheated them in it, programmed the computer to heat up to 450° F. and hold there. (I tried 250°, but it wasn't hot enough to boil off the water before the glaze ran off.) I had one bowl develop cracks from the thermal shock, and a couple that didn't take on enough glaze, but out of 15 bowls, 12 were good to go in the firsts box.
On the left, you can see what the bowls looked like coming out of their first firing, and what they look like after the glaze dip. On right, after the firing.
*(My white glaze also likes to do this, which is why I mix a generous teaspoon of epsom salts into each bucket. Apparently I should have done likewise the last time I mixed up Dragon Green.)