# Applying Underglazes: Brushwork and Layering

Unit: Surface Decoration (Pre-Bisque)
Topic: Applying Underglazes
URL: https://claybook.studio/learn/applying-underglazes-brushwork-and-layering/

# Getting Even Color

The most common problem with underglaze application is uneven coverage: streaky, patchy color that looks amateurish after firing. The fix is almost always technique and patience.

## Brushes and Tools

*   **Flat wash brushes**: Best for covering large areas evenly.
*   **Round detail brushes**: For fine lines, dots, and detailed motifs.
*   **Fan brushes**: For blending and soft gradients.
*   **Sponges**: For stamped textures and soft, dappled coverage.

Use soft-bristle brushes designed for ceramics. Stiff brushes leave obvious brush marks that show after firing.

## The Three-Coat Rule

One coat of underglaze is almost never enough for solid, opaque color. The clay absorbs the first coat rapidly and the color looks thin and washed out.

Apply **three thin coats**, letting each coat dry to touch before adding the next. This builds up consistent, opaque coverage.

*   Alternate brush stroke direction with each coat (horizontal, then vertical, then diagonal) for the most even result.
*   Between coats the surface will look lighter as it dries; this is normal.

## Staying Inside the Lines

On greenware, underglaze bleeds slightly into the porous clay surface. To get crisp edges:

*   Work quickly and do not overbrush the same area.
*   Use a fine round brush with a good tip.
*   Clean up edges with a damp brush or damp sponge while still wet.

## What Happens in the Kiln

During bisque firing, the binders in the underglaze burn away and the color is locked into the clay. The surface will look slightly matte and dull; this is correct. The final glaze coat, applied after bisque, gives it depth and gloss.

## Pro Tip

Test all your underglaze colors on a test tile before committing to a piece. Colors can shift dramatically between the raw state and the final fired result.

## Coverage Control Routine
For each color field:
* Coat 1 thin pass
* Dry to touch
* Coat 2 cross-direction pass
* Coat 3 correction pass

Layer discipline prevents streaking and patchy opacity.

## Dig Deeper

The brown and amber tones in many underglazes come from [manganese dioxide](https://en.wikipedia.org/wiki/Manganese_dioxide), a compound also used in batteries and industrial chemistry. For a wider view of how colored coatings interact with fired clay, the Wikipedia article on [ceramic glaze](https://en.wikipedia.org/wiki/Ceramic_glaze) explains the relationship between underglazes, overglazes, and the glassy surfaces that seal them.

## Check your understanding

### Question 1: How many coats of underglaze are typically needed for solid, opaque coverage?

- [ ] A. One thick coat
- [x] B. Three thin coats
- [ ] C. Two coats only
- [ ] D. As many as possible without drying

Tip: Three thin coats, with each one allowed to dry to the touch before the next is applied.

### Question 2: Why should you test underglaze colors on a test tile before using them on a finished piece?

- [ ] A. To check the underglaze has not gone off
- [x] B. Colors shift in the kiln and testing prevents surprises
- [ ] C. Test tiles use less clay
- [ ] D. It is only required for professional potters

Tip: Colors can shift significantly between raw application and the final fired result, so testing prevents nasty surprises.

### Question 3: After three coats of underglaze on greenware, you see fine cracking in the color layer but not in the clay. What is the safest response?

- [ ] A. Ignore it; the clear glaze will hide the cracks
- [x] B. Lightly scrape back the cracked area and re-apply in thinner coats
- [ ] C. Add a very thick fourth coat to seal the cracks
- [ ] D. Wet the surface heavily to re-dissolve the underglaze

Tip: Hairline cracking in a thick underglaze layer can cause flaking later. It's safer to lightly scrape back and re-apply thinner coats than to ignore it.