Common Glaze Problems and How to Fix Them

Even experienced potters get glaze problems. Most come from a handful of causes that are easy to avoid once you know them. Here are the most common issues and what to try.

Crawling

What it looks like: Glaze pulls back into beads, leaving bare patches.

Common causes: Dust or oils on the bisque, glaze applied too thickly, or glaze applied over a dry, dusty surface.

Fix: Wipe bisque with a damp sponge first (see prepping bisque), apply thinner coats, and avoid touching surfaces.

Pinholing

What it looks like: Tiny holes in the glaze surface.

Common causes: Gases escaping from the clay or glaze during firing, or glaze too thin or too thick in places.

Fix: Make sure the bisque is clean, apply even coats, and consider a slower firing or a short hold at peak temperature if your kiln allows.

Running and dripping

What it looks like: Glaze flows down and pools at the bottom or fuses the piece to the shelf.

Common causes: Too much glaze, glaze on the foot, or firing too hot for the glaze.

Fix: Apply thinner coats, wipe the foot clean, and use kiln wash and stilts (see kiln furniture basics).

Crazing

What it looks like: A network of fine cracks in the glaze surface.

Common causes: The glaze and clay body shrink at different rates, so they don't fit.

Fix: Use glaze rated for your clay body and firing range. Crazing can make food or drink pieces unsafe, so don't use crazed pieces for food.

Blistering

What it looks like: Bubbles or craters in the finished glaze.

Common causes: Firing too fast or too hot, or glaze applied too thickly.

Fix: Fire to the cone listed on the label (see firing glazed ceramics) and apply thinner coats.

Color looks different than expected

Common causes: Too few coats, different clay color, or firing temperature. Glaze color in the jar rarely matches the fired result.

Fix: Test on a tile first, follow the recommended number of coats, and fire to the right cone.

Prevent most problems

• Always test new glazes on a scrap tile.
• Use glaze made for your clay body's firing range.
• Keep coats even and not too thick.
• Clean the foot and use kiln wash.

Shop glazes and clear glazes, and see our guide to glazing bisqueware.