What makes a glaze reactive
A reactive glaze contains materials that move, crystallise or pool during firing. Iron, titanium and rutile are common; so are deliberately coarse particle sizes. At 1230C the glaze is a fluid, and its final surface depends on how thickly it was applied, how the piece sat in the kiln, and where it was relative to the flame path.
The result is a surface that breaks from one colour to another across a single plate — darker where the glaze pools in a curve, lighter where it thins over a rim.
Why buyers either love it or hate it
Reactive glaze is the fastest route to a premium, artisan-positioned range. It signals handcraft without requiring hand painting on every piece, which keeps the unit cost within reach of mid-market retail.
The complication is specification. A buyer who approves a photograph is approving one specific break pattern. Production will deliver a distribution of patterns, all within the process, none of them identical to the photo.
Writing a tolerance you can enforce
This is the part worth getting right during sampling. A workable specification has three components:
- An approved sample set, not a photo. Sign off three to five physical pieces that represent the acceptable range of variation — the lightest and darkest extremes included.
- A colour range, not a colour. Define the acceptable band, ideally with Pantone references for both ends.
- A coverage rule. State whether pooling, crazing or pinholes are acceptable, and at what density.
With those three fixed, QC can inspect against a standard instead of an opinion.
Reactive glaze versus the alternatives
| Technique | Variation | Unit cost | Best for |
|---|---|---|---|
| Reactive glaze | High | Mid | Premium and artisan ranges |
| Solid colour glaze | Very low | Low | Volume basics and matched sets |
| Hand painting | Highest | High | Statement pieces, gift ranges |
| Silk-screen | None | Low | Logos and repeatable graphics |
| Decal | None | Mid | Full-colour artwork, fine detail |
Most ranges mix two: a reactive body for the hero bowl, solid glaze for the plates that must match across reorders.
Practical notes for reorders
Reactive glaze is sensitive to raw material batches. Keep a retained physical sample from every production run — it is the only reliable reference when comparing a reorder two seasons later.
If colour consistency across reorders is commercially critical, say so at briefing stage. We can shift the formula toward a more stable glaze, trading some variation for repeatability.
Frequently asked questions
Is reactive glaze food safe?
Yes. Reactive glazes fired at 1230C are food safe when formulated and tested for the intended use. Testing requirements vary by market — tell us the destination and we will confirm.
Will two production runs match?
They will sit within the agreed range, not match each other piece for piece. Retain a physical sample from each run as your reference.
Can the effect be reproduced in a decal?
No. A decal is a printed image under or over glaze; it cannot reproduce the depth of a reactive break. Use decal for graphic patterns, reactive glaze for surface character.
Conclusion
Reactive glaze is not a defect and not a shortcut — it is a specification choice. Buyers who treat it that way get the premium look without the disputes. Buyers who approve it from a photograph spend the first production run arguing about what the sample meant.
Approve physical pieces, write down the range, and the rest follows.