Don't want to mess up? Read this! Common Mistakes from BOTZ Unidekor Users and How to Fix Them

by Chanicha T

 

Have you heard that in the world of ceramics, "the kiln is the true score-cutter"? Because sometimes, a beautifully drawn piece in its raw state comes out of the kiln with frustrating problems, such as faded colors, glaze crawling, or blurred designs.

But to prevent your work from "failing" before it shines, Pottery Clay has compiled the 5 most common mistakes potters make when using BOTZ Unidekor, along with their causes and step-by-step solutions.

1. Faded or missing colors after firing

Have you ever painted a vibrant, clear color, only for it to come out of the kiln faded and almost blending into the clay body?

The common cause is applying the color too thinly. Because BOTZ Unidekor is highly concentrated, if too much water is added or the brushstrokes are too thin, there won't be enough pigment to cover the surface of the piece. Although this color set can withstand temperatures up to 1250°C, some color shades (especially warm tones like red, pink, and orange) may start to degrade or lose their vibrancy when fired at very high stoneware temperatures.

Here's how to fix it:

  • Apply 2-3 layers of color, waiting for each layer to dry before applying the next, to achieve the correct pigment thickness.
  • If firing at temperatures of 1200°C or higher, it is recommended to conduct a test firing for each specific color shade beforehand to observe any changes in color.

 

2. Glaze crawling in the painted area

This problem is evident after glaze firing, where the clear glaze retracts from the decorated areas, leaving dull, exposed spots on the surface.

There are two common causes:

  1. Too thick application of color creating a dusty layer. If the color is applied too thickly, the pigment forms a thick, dusty layer that prevents the clear glaze from adhering to the clay body underneath.
  2. Surface contamination from grease or dust. Bisque ware with clay dust or oil from hands can prevent color and glaze from adhering to the surface.

Here's how to fix it:

  • Always use a clean, damp cloth to wipe dust off bisque ware before applying color.
  • Apply color smoothly, avoiding lumps. If too much is applied, gently brush off the excess powder with a clean brush before glazing.

 

3. Blurred colors and melting, imprecise lines

You intended to draw sharp, minimalist lines, but after firing, the lines are blurred, the edges have melted and spread, or they've run, distorting their shape.

There are two common causes:

  1. Glaze reacting with color. Some clear glaze formulas have a high flux content, which causes the pigment to migrate and flow with the glaze at high kiln temperatures.
  2. Over-soaking at high temperatures. Prolonged soaking causes the color and glaze to melt and blend excessively.

Here's how to fix it:

  • Choose clear glazes specifically labeled "non-running" or glazes designed for painted designs, such as BOTZ's own clear glazes.
  • Avoid using glazes with high zinc content (zinc-free glaze) with certain color shades, as zinc often reacts to change or blur colors.

 

4. Air bubbles or pinholes on the glazed surface

The ceramic surface exhibits small pinholes or exploded air bubbles where color was applied.

There are two common causes:

  1. Color or clay is still damp. Glazing and firing the piece while the applied Unidekor color is not completely dry. Trapped moisture then pushes its way out during firing.
  2. Gases in the color cannot escape in time. Raw pigments release gases at lower temperatures, but if the clear glaze melts and seals the surface too quickly, these gases become trapped and form bubbles.

Here's how to fix it:

  • After applying color, allow it to dry completely for at least a few hours or overnight before applying glaze.
  • Slow down the firing program in the 100–600°C range to allow all moisture and gases to evaporate before the glaze begins to seal the surface.

 

5. Color peeling off the clay body after firing

Upon opening the kiln, the Unidekor color has flaked off like peeling house paint, coming off in chips.

The common cause is incompatible shrinkage. The type of clay used and the Unidekor color have vastly different shrinkage rates when exposed to heat. This often occurs with certain types of high-vitreous clays or clays that shrink significantly.

Here's how to fix it:

  • Always perform glaze tests beforehand. This is the best way to check the compatibility of "clay + color + glaze."
  • If you encounter this issue with your current clay body, try using the in-glaze method (glazing first and then painting on the raw glaze) to help the glaze adhere and integrate the color better with the ceramic surface.

Ceramic work is an art that requires observation and learning from mistakes. These problems are natural for all potters. If you follow the correct steps: wipe dust off the piece > apply an appropriate thickness of color > let it dry completely > choose the right clear glaze 

If you are new to BOTZ Unidekor, don't conclude that a color is "difficult to use" after only one try. Try adjusting only one variable at a time, and you will understand the behavior of the color more quickly.

If you are looking for help or would like more advice on firing techniques and glaze selection, please visit Pottery Clay to chat and purchase a full range of BOTZ brand products.

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