Shivering is the mirror-image defect to crazing. Instead of the glaze cracking under tension, it is compressed so tightly against the clay body that it buckles and flakes away, often starting at rims, edges, or handles where the piece is thinnest and the stress concentrates.
Crazing and shivering come from the same underlying cause: a mismatch between the glaze's and the body's coefficient of thermal expansion (CTE)The fractional amount a material's length changes per degree of temperature change. A small mismatch between a bonded glaze and body layer creates real stress because fired ceramic is brittle., pointed in opposite directions. In crazing, the glaze wants to shrink more than the body allows and ends up in tension. In shivering, the glaze wants to shrink less than the body, so as the body contracts around it on cooling, the glaze is squeezed into compression. Fired ceramic handles compression reasonably well up to a point, but too much of it makes the glaze layer buckle and shear off, usually in sharp, curved flakes rather than a network of cracks.
Because the underlying diagnostic is identical to crazing, the fix is the same toolkit run in reverse: shivering calls for raising the glaze's expansion (or lowering the body's) rather than lowering it. More alkali flux (Na₂O, K₂O) pulls a glaze's expansion up; reducing silica or alumina, or backing off calcium, magnesium, or zinc fluxes in favor of alkalis, has the same effect.
Shivering is not just cosmetic. The flakes it produces are often glass-sharp, and because they tend to let go at rims and edges (exactly where a piece gets handled or put to the mouth), a shivering glaze is generally treated as a functional-ware defect to fix, not just a visual one.
Shivering can be hard to catch immediately after firing, since a glaze under compression does not necessarily flake the moment the kiln cools; flaking sometimes only shows up days, weeks, or even years later, after ordinary handling stress (a knock, a temperature change, a chip starting at an edge) finally releases the built-up stress. A piece that keeps losing small flakes of glaze at the rim or foot well after firing, with no obvious impact damage, is a common way shivering first gets noticed rather than being caught on inspection right out of the kiln.