The Slow Start That Saves Everything

Candling is the practice of holding the kiln at a very low temperature (typically 80–120°C (175–250°F)) for an extended period at the beginning of a firing. It is a safety measure, and it is one of the most important habits in ceramics.

Why Candle?

Even pots that appear completely bone dry can retain trace amounts of atmospheric moisture absorbed from a humid studio. Bone-dry clay is also still physically porous, and in a humid environment, it re-absorbs water from the air over time.

When candling:

• The kiln heats slowly, giving any remaining moisture time to evaporate gently as water vapor rather than steam.
• The heat moves evenly through thick sections without building up the pressure that causes explosions.
• It acts as an insurance policy, especially valuable for thick-walled pieces, large forms, and any work that was rushed in drying.

How Long to Candle?

The standard recommendation:

• Thin-walled pieces (mugs, bowls): 1–2 hours of candling at 80–100°C.
• Medium pieces (vases, larger bowls): 2–3 hours.
• Thick pieces (sculpture, large vessels): 3–6 hours or more.

If you are unsure, err on the side of longer. Candling adds a little time to the total firing but costs almost nothing in electricity and prevents the catastrophic loss of an entire kiln load.

Candling Decision Guide

Choose duration by highest-risk piece:

• If one thick piece is present, candle for thick-piece timing
• If humidity is high, add extra hold time
• If unsure, extend rather than shorten

Candling time is cheap compared to load failure.

Go Deeper

Candling is the gentlest phase of a process that eventually leads to sintering, where clay particles permanently fuse together at higher temperatures. The Wikipedia article on kilns explains how different kiln designs manage the slow temperature ramps that make candling effective.