Classifications of the Decal Production Process

Table of Contents

Decal definition

Decal classification

on-glaze decal

In-glaze

Under-glaze technique

What’s next

Decal definition

Have you ever wondered how did the custom-made design of bone porcelain produce? What’s the technology involved?

The main way to realize the custom-made design of bone China products, either it’s bone china mugs, or plates, or bowls, is decal technology. Decal, also known as water transfer decals, is a decorative process in which designs are first printed on a special paper pre-coated with water-soluble Glue, then soaked in water, and then transferred to the surface of bone China products. The decal paper consist of 3 layers, the bottom of the paper (also known as paper-based), the middle layer is Sol, and the surface of the cover oil.

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Decal classification

According to the production process, the decal paper production can be classified into three categories, which are on-glaze color, in-glaze color, and under-glaze color.

On-glaze decal

Bone porcelain that made of on-glaze technology is by directly applying the decal paper on the glazed surface, or paint directly on the surface of the bone porcelain, and then fired at 700-850 °C.

Because the firing temperature did not reach the melting temperature of the glaze layer, so the designs remain to stay at the surface and can not sink into the glaze layer,. If you touch with your hands and rub carefully, you will find that the surface of the product has a concave-convex sense, and you can observe uneven height with your eyes. On-glaze color is the main technical methods used in the massive bone porcelain production with its features of bright color, mature technology, easy to operate, and low price.

In-glaze

The firing temperature of the in-glaze technology is higher than that of the on-glaze, which reaches the melting temperature of the product glaze. The Ceramic Pigment sinks into the glaze when the glaze is melted and is covered by the glaze layer after cooling. If you touch the surface of the bone porcelain products, there is no obvious concave-convex feeling, its wear resistance is good, high surface brightness, high product grade, the cost is also relatively high.

The technology for the in-glaze decal is difficult, and the requirements for porcelain, kiln, and paper are strict. The test results of lead and cadmium can meet the requirements of the FDA and California Standard. This is a development direction of the ceramic field since people are paying more and more attention to the safety of the products.

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Under-glaze technique

Under-glaze colored ceramics is a traditional decorative method in China.

All the colors of the products are decorated on the ceramic body and then glaze. After glazing, the products are fired once at a high temperature. Like the in-glaze technology, the surface is covered with the glaze layer, and the surface is bright and smooth, there is almost no sense of elevation. As a result of high firing temperature, the colors are easy to diffusion during the process, making it’s difficult to realize good decorative fine patterns effect, so the patterns used in under-glaze decoration, in general, are relatively simple.

With the color and pattern restrictions, under-glaze technology is unlikely to become the mainstream of the daily porcelain decoration method. Because of the features of high cost, the color is not abundant and the technical difficulty of in-glaze technology when comparing to on-glaze, the lead-free on-glaze decoration is the main development direction of ceramic decoration with no doubt.

What’s next

After the bone porcelain is decorated with the designs, it must be fired in the kiln at a certain temperature to make the designs permanently stay, this process is called decal firing. Different materials require different firing temperatures. After the appropriate temperature fired, the finished products are with bright colors, with patterns or designs stick to the porcelain surface, that’s not easy to scrape.