Most beginners approach glazing the way they approach painting: pick a colour, brush it on, done. The results are usually disappointing. Uneven coverage, crawling, bare patches, or glaze that runs off the piece and fuses it to the kiln shelf. Glazing is not painting. Understanding what glaze actually is, and what it does in the kiln, changes everything about how you apply it.
What ceramic glaze is ¶
Glaze is a layer of glass-forming minerals applied to the surface of a clay body before firing. At high temperatures, these minerals melt and fuse to the clay surface, forming a glassy layer. The colour of the glaze comes from metal oxides added to the base: iron oxide for browns and greens, cobalt for blue, copper for turquoise and green in oxidation or red in heavy reduction. At Granite Crest Zone, intermediate students mix two glazes from raw materials. Silica, feldspar, whiting, and a colourant. So that they understand what they are working with before they apply it.
Bisque firing and why it matters ¶
Before glazing, a piece is bisque fired to approximately 950°C. This burns off the organic material in the clay and makes the piece hard enough to handle, but still porous enough to absorb the glaze suspension. If you apply glaze to unfired clay (raw glazing), the water in the glaze softens the clay and can cause cracking or warping. Bisque firing is the step that makes consistent glazing possible. At Granite Crest Zone, all beginner pieces are bisque fired between session five and session six, and glazing happens in session seven.
Application methods and their results ¶
The three main application methods are dipping, pouring, and brushing. Dipping gives the most even coverage and is the method we use for most studio pieces. The piece is submerged in a bucket of glaze for three to five seconds, then held upside down to drain. Pouring is used for the inside of tall forms that cannot be dipped easily. Brushing is the least consistent method for beginners because it is hard to apply an even thickness by hand, but it is useful for applying a second glaze over the first in a specific pattern.
Thickness and why it matters ¶
Glaze needs to be applied at a consistent thickness. Typically 1-2 mm for most stoneware glazes. Too thin and the glaze will not melt fully, leaving a dry, rough surface. Too thick and the glaze will run during firing, potentially fusing the piece to the kiln shelf. The thickness of the applied glaze depends on the specific gravity of the glaze suspension (measured with a hydrometer) and the porosity of the bisque piece. At Granite Crest Zone we measure specific gravity for every glaze bucket at the start of each session and adjust with water or dry material as needed.
The foot ring: the one place glaze must not go ¶
Every piece must have its foot ring wiped clean of glaze before it goes into the kiln. If glaze is left on the foot ring, it will melt and fuse the piece permanently to the kiln shelf. This is the single most common mistake beginners make. At Granite Crest Zone we check every piece before loading. If the foot ring is not clean, the piece comes back out for wiping. It takes thirty seconds and saves the piece.
Glazing well is a skill that takes time, but the fundamentals are learnable in a single session if you understand what you are trying to do. The intermediate course at Granite Crest Zone covers glaze chemistry, application, and testing over three dedicated sessions.