Botz Glaze FAQ

How often should I apply BOTZ glazes ?

In general, 2 – 3 layers, except for the two transparent glazes (BOTZ 9102 and BOTZ 9106) and the two crackle glazes (BOTZ 9351 and BOTZ 9352). Apply only a thin layer of the latter, i.e., without dilution or 1 – 2 times slightly diluted. For red colours and gold glaze, rather apply 3 times, see question 5.

How long is the shelf life of BOTZ glazes ?

After the purchase from the dealer, the glazes will have an average shelf life of 2 – 3 years, some even distinctly longer. Good storage conditions, i.e., no extreme temperature variations, no frost, no heat will extend the shelf life. Solidified glazes can be stirred with water to become spreadable again.
Tip: thoroughly clean the container edge after use, add some water to the container, stir in with next use.

What is the biscuit firing temperature ?

The first firing (biscuit firing) traditionally was fired at 900° to approx. 960°C. For powder glazes, a porous biscuit ware was important so that the mixed powder glaze could adhere roughly to the biscuit ware. However, BOTZ Flüssigglasur can be applied very well to ware biscuit fired at distinctly higher temperatures as it contains a glue which helps the glaze to adhere firmly. Advantage of a biscuit firing temperature of approx. 1020 – 1050°C: with a high biscuit firing temperature, the clay´s gassing process has been concluded to the greatest extent and the glaze will not be “disturbed” by clay gases in the 2nd firing, i.e., there will be less bubbles and craters. Some BOTZ users fire stoneware clay in the first firing at approx. 1220 – 1250 °C, thus the clay is sealed and frostproof and then, they use BOTZ Flüssigglasuren for the earthenware range at 1050°C.

Can I mix BOTZ glazes with each other ?

Very beautiful results can be achieved when you apply one glaze on top of the other. Mixing the glazes into each other in the earthenware range will not yield exciting results with all of them. Well suited are opaque glazes without effect and in particular also BOTZ Steinzeug (see also Notes under Tips Steinzeug).

Red will not turn red, Gold will not turn gold, what happened ?

Red and gold colours in ceramics often are very sensitive. Very stable are red BOTZ colours (BOTZ 9601 – BOTZ 9605) and BOTZ Gold (BOTZ 9541) when you observe the following 3 rules:

1. Apply a thick layer
2. Fire at low temperature (i.e., up to 1040°C)
3.Admit oxygen to the kiln, or do not set the ware too close inside the kiln so that air can circulate easily.

For Lava (BOTZ 9606) and Korale (BOTZ 9607), you can fire at a higher temperature, however, carefully observe the oxygen supply. White edges are part of the appearance with these glazes.

Can I overglaze already fired glazes again ?

Most of the time, this works pretty good, if you, for example, applied a thin layer and wish to apply the same glaze again. The drying time on fired glaze, of course, is longer than on unglazed biscuit ware. If you wish to apply a different colour over a fired glaze, the result is not quite foreseeable, but often exciting. For good adhesion, you can heat the fired ceramics again to 60 – 100 °C prior to renewed glazing.

Some BOTZ glazes smell during firing, will toxic gases escape ?

It is important to know that each firing, i.e., also a biscuit firing, produces harmful gases in the ceramics.You should exhaust these fumes with an exhaust air system (e.g., see or provide for good ventilation and aeration in the firing chamber and, if possible not work inside the firing chamber during firing. The sometimes intense smell of BOTZ glazes (approx. between 200 – 300°C) is no more dangerous than inodourlessly firing glazes. Interpret it as a hint for insufficient ventilation. The bad smell annoyance during firing will decrease if you let the glazes dry thoroughly before firing.

Are BOTZ glazes "food-safe"?

The term "food-safe" does not exist in the ceramics industry. It is important to use only lead-free and, if possible, only completely non-toxic glazes for dishes and drinking vessels. Some glazes are not acid-stable, i.e., if contacted by light acids, substances of contents may be dissolved from the fired glaze. Although all BOTZ liquid glazes are non-toxic, we recommend for safety's sake for dishes and drinking vessels only those glazes which are particularly resistant and marked by the "recommended for tableware" pictograph. For reasons of hygiene, this does not include, e.g., effect glazes or mat glazes as food residues may be taken up here.

Is there an optimum firing curve for BOTZ glazes ?

You can fire BOTZ Flüssigglasuren (earthenware) very well with the firing curves already pre-programmed in the control system, they do not require any specific firing curve to be entered. If you do your own settings, heat up to a temperature of approx. 600°C with approx. 100°C per hour, then apply full load until the maximum temperature of 1020 – 1060 °C has been reached, with a soak of 10 – 20 min. All samples in the catalogue were fired at 1050 °C with a 15 minute soak (except for Red and Gold, see question 5). Please note that a kiln frequently fires at higher temperatures in the upper range than in the lower range.

Stoneware glazes are to be fired with the same heating speed up to 1220 – 1280°C with 10 – 30 minutes soak, ideal is a final temperature of 1250°C.

Can I order from you directly ?

BOTZ Flüssigglasuren are distributed exclusively through specialized dealers for ceramics needs, craftwork shops and mailorder businesses. We would be pleased to give you the name of a dealer near you.

Are BOTZ glazes frost-proof ?

Frost-proofness is primarily determined by the clay rather than by the glaze. If the clay has been "sintered", i.e., it is sealed and cannot absorb water, it is perennial. Please ask your clay supplier for the sintering temperature of your clay. Liquid glazes can be applied also on highly biscuit fired ware, see also Question 3.

Are there any safety data sheets for BOTZ glazes ?

Most of the dealers have a CD-ROM with all BOTZ safety data sheets and can give you a printout of the requested data. Or contact us directly, we will be glad to be of assistance and send you the requested safety data sheets.

My glaze has run off strongly during firing, what is the reason ?

Our program includes some glazes which are intended to run off (see pictographs in the catalogue); in this case, just apply a thin layer to the lower area of your object. If, however, other glazes run off, the layer could be too thick or the temperature too high. Perhaps, you should verify the actually achieved kiln temperature by means of melting cones.