Shivering is a ceramic glaze defect that results in tiny flakes of glaze peeling off edges of ceramic ware. It happens because the thermal expansion of the body is too much higher than the glaze.
Conclusion. To summarize, it's possible to glaze fire pottery twice or even multiple times. Fired pottery can be glazed several times to add textures, accents, and effects, and multiple firings are possible.
If your glaze has some clay but less than 10%, I would add 1% bentonite. This should be enough to keep your glaze suspended and prevent hard-panning. If you're mixing a new glaze with little to no clay in it, you can add the bentonite to your recipe to start out with.
If the glaze is too thick or the cracking is severe, please wash all the glaze off your pot, let it dry at least overnight, and try to glaze again another day.
Underglazes contain a small amount of gum, which makes it easier to control when painting them onto your ceramics. Apply two to three coats. Make sure you wipe off any glaze from the base of your piece before setting it aside to dry.
It happens because the thermal expansion of the clay body is incompatible with the glaze or underglaze (e.g. the bisque and glaze shrink or expand at different rates). Most things expand when hot and shrink/contract when cool. A clay body and glaze fuse together during firing.
Glaze crazing or glaze crackle is a network of lines or cracks in the fired glazed surface. It happens when a glaze is under tension. A craze pattern can develop immediately after removal from the kiln or years later.
Some potters will put their glazed ware straight into the kiln and fire it immediately. However, glaze contains water, and this is absorbed by bisque ware when glaze is applied. Ideally, leave your pottery overnight after glazing to allow this water to evaporate. Or add a pre-heat to your firing schedule.
The heavy particles, light particles and water must be mixed together really well so the glaze becomes homogenized. This means that every inch of the glaze bucket has the exact same composition.
Prepare the glaze according to the directions on the recipe. Allow the glaze to cool before applying it to the cake. The glaze should be the consistency of corn syrup. Test the consistency by taking a spoonful from the bowl and drizzle back into the glaze; the drizzled glaze should leave a trail.
Epsom salt additions can be invaluable for glazes, its enables creating a thixotropic (gelled) slurry that applies evenly, holds in place and goes on in the right thickness on porous or dense bisque ware. When the slurry has a sympathetic specific gravity, about 2g per gallon of epsom salts should gel it.
Using Wax Resist Over Glaze
Use Wax over glaze to create patterns when layering glazes. Let your wax dry for several hours (when applied over glaze) before layering a second glaze. Often it is best to apply wax the day before you will dip the second glaze. Cover the wax jar so it doesn't dry out.
Use Less Food Gel to Color the Icing
The more gel I added the more I asked myself, “Why does royal icing bleed?” Once the gel is added to the icing, the colors begin to darken. It continues to darken even after you pipe it onto your cookies. So it makes sense to use less gel and therefore you will have less bleeding.
Overfiring results in glazes that begin to run. The glaze coat may be thinner at the top of the pot and thicker at the bottom. Glaze may even run off the pot and drip onto the kiln shelf or other pots. Seriously overfired pots may show pinholing and pitting as the glaze reaches evaporation temperature.
Typically, three coats are applied. Each dries slowly, hardening as it does so (the glazes contain binders). This provides a stable base for the next one.
One technique you may not have used is multiple firings. Some people fire a single piece 3, 4 or even more times until they get exactly what they like. The only rule in multiple firings is that you can't re-fire at a hotter temperature than a previous firing, or you will burn off the lower temperature glaze..
Your glaze should be the consistency of heavy whipping cream, thick but not too viscous. If you find that your glaze is too thick, try adding small amounts of water slowly, until it reaches the proper consistency. While adding water to your glaze, be sure you are stirring it constantly.
Dip Glazing is the process of dipping pottery in a glaze for three to five seconds. It's the fastest way to glaze ceramics with even layers, but potters also use it to create a base for other finishing techniques.
So, can you brush on dipping glaze? Yes, you technically can, but it may not produce the ideal results. Commercially prepared brushing glaze contains additives like CMC gum (brushing medium) that helps you brush the glaze on clay, while most dipping glazes are free from it.
Once you have applied glaze to your pot it is immediately ready for the glaze firing, but leaving it on a shelf for a few weeks until you're ready to bring it in is fine too.
As a general rule of thumb, for 1 lb of dry glaze powder, use 11 ounces of water for dipping glaze, 8 ounces of water for spraying glaze, or 7 ounces of water for brushing glaze. Or, 25 lbs makes about 3 gallons. This is only a starting point.
Another advantage is that you won't risk messing up your design when you apply the clear glaze. However, you can apply the clear glaze right over the top of the underglaze without a firing between. This is best done if you applied your underglaze to bisque, because greenware can absorb glaze and crack.
Temperature and humidity changes which causes the glaze to crack. It can be caused by moisture getting into the glaze and forcing cracks in the glaze. It can be caused by being bumped or knocked repeatedly, causing small cracks in the glaze.
When a glaze cracks as it dries on a pot, it usually means that the glaze is shrinking too much. This is normally caused by having too much plastic material (ball clay) in the glaze. If this is the problem, it should exist from the beginning (not appear two months later).
Crazing is due to a thermal expansion mismatch between body and glaze. As a piece of ware is heated and cooled during normal use, it expands and contracts. An incompatible clay and glaze usually means the glaze either immediately or eventually fails by crazing or shivering (the former being more common).