4 types of underglazes potters should know
There are 4 categories of underglaze. Let get to know them so you know which one is best for your ceramic work.
- Low fire underglaze offers colorful vivid colors with firing temperatures between 950 - 1150 °C. Prepare 80 - 95% pigments such as stains with low firing temperature mixed with 10 - 20% kaolin. Some pigments with high heat resistances can be added with frits, normally borax frits because they are lead free while the colour response is not affected. The underglaze is fired at low firing temperature. It is used to decorate white earthenware, dolomite and bone china.
- High fire underglaze has a limited variety of cone from 1200 - 1400 °C. Prepare stains with high firing temperature mixed with kaolin at the portion of 80 - 95% stains: 10 - 20% feldspar. The glaze will be mixed with additives such as gum solution and glycerin which will make it easier to pain. Do not mix the glaze with the pigment to reduce heat resistance because there are chemicals in the glaze that will have reaction to the pigment. Underglaze is available in powder and liquid. It is normally go through single firing.
- Specialty underglaze is not popular compared to the first two categories. It requires low firing temperatures from 500 - 800 °C. Its effect is not consistent. Potter has to be very careful when preparing solutions which are mostly hazardous. The coloring solutions are fluid and easy to evaporate.
- Other underglazes Underglaze chalk crayons and pencils are popular among students and potters. They are ideals for decorating ceramics and easy to use compared with watercolor painting. The underglaze chalk crayons are suited for personal creation. They are not appropriate for industrious production because they can be easily erased. Sometimes the pigments can fall in the glaze which will result in defect.