Do you have questions about the optimal firing temperature or the use of BOTZ glazes? We're more than happy to help. Here you will find a compilation of the most frequently asked questions. If you have individual questions, please send us an email to We look forward to your message.

The most frequently asked questions

We recommend applying the Botz glazes 2-3 times unless otherwise stated in the instructions on the tin. For example, the two transparent glazes (9102 and 9106) and the two craquelé glazes (9351 and 9352) are applied only once undiluted or slightly diluted once or twice. Red shades should generally be applied more like 3 coats to ensure an intense colour. For a better application, you can dilute the BOTZ glazes with a little water.

After your purchase from us, the glazes last an average of 2-3 years - some even much longer. Good storage conditions, ie no large temperature fluctuations (no frost, no heat) extend the storage time. Thickened glazes can be stirred with water so that they are spreadable again.

Tip : clean the rim of the can well after use, put some water in the can and only stir it in the next time you use it, or pull cling film over the edge of the lid, which also counteracts drying out.

The first firing (bisque firing) was traditionally between 850°C and 900°C. A porous body was important for powder glazes so that the mixed powder glaze adhered to the body. However, BOTZ glazes can be applied very well to higher-biscuited goods, as they contain an adhesive that allows the glaze to adhere firmly. Advantage of a baking temperature of approx. 950°C : at a high baking temperature, the outgassing process of the clay is largely complete and the glaze is not "disturbed" by clay gases in the second firing, ie there are fewer bubbles and craters.

You can get very nice results by applying one glaze to another. Stirring the glazes together in the earthenware area does not always produce exciting results. Opaque glazes without an effect are well suited (e.g. the matt glazes 9107, 9108, 9487-9491 and 9612) and BOTZ stoneware in particular (see information under tips on stoneware in the current BOTZ catalogue).

Red and gold tones in ceramics are often sensitive. BOTZ red tones (9601 – 9605) and BOTZ gold (9541) are very stable if you observe 3 rules of conduct:

1) apply thickly, 2) burn low (ie up to 1040°C) 3) allow oxygen in the kiln, or do not place too tightly in the kiln so that the air can circulate well.

With lava (9606) and coral (9607) you can burn higher (optimal 1050°C), but you have to pay attention to the oxygen supply. White edges are part of the appearance of these glazes, a very insensitive red is 9611 lacquer red.

This usually works very well, especially if you e.g. B. applied too thinly and then want to apply the same glaze again. The drying time on fired glaze is of course longer than on unglazed body. If you want to apply a different color over a fired glaze, the result is unpredictable but often exciting. For good adhesion, you can reheat the fired ceramic to 60 - 100°C before glazing again.

It is very important to know that every firing in the ceramic, ie also a biscuit firing, gives off gases that are harmful to health. You should discharge these exhaust gases with an exhaust air system (e.g. at ) or ensure good ventilation in the combustion chamber and avoid working in the combustion chamber during the fire if possible. The sometimes strong smell of BOTZ glazes (approx. between 200 - 300°C) is no more dangerous than glazes that burn without smell. Use the smell as an indication of insufficient ventilation. The odor load during firing decreases if you allow the glaze to dry thoroughly before firing.

The term "food-safe" does not exist in ceramics. It is fundamentally important not to use any glazes containing lead and, if possible, only to use glazes that are completely label-free for eating and drinking utensils. We subject our glazes to an acid and alkali test according to the DIN standard. Those glazes that pass the test receive the pictogram "Recommended for crockery and tableware" - so you're on the safe side. Some glazes are not acid-stable, ie ingredients in the burned glaze can be dissolved in contact with light acids. Therefore, to be on the safe side, we do not recommend using these colors for the inside of eating and drinking utensils. For reasons of hygiene, effect glazes or matt glazes, for example, belong to this group because food residues could also be deposited here.

You can fire BOTZ liquid glazes (earthenware) very well with the firing curves that are usually already pre-programmed in the control, they do not require a special firing curve to be entered. If you set it yourself: heat up to approx. 600°C at approx. 150°C per hour, then full load up to the maximum temperature of 1020 – 1060°C with a holding time of 10 – 20 minutes.

All samples in the BOTZ catalog are fired at 1050°C with a holding time of 15 minutes (with the exception of red and gold). Please note that a stove often burns higher at the top than at the bottom.

Stoneware glazes are to be fired at the same heating rate up to 1220 - 1280°C with a holding time of 10 - 30 minutes, a final temperature of 1250°C is optimal here.

The frost resistance is not primarily determined by the glaze, but by the tone. When the clay is 'sintered', meaning it's dense and can't absorb any more water, it's hardy. Please ask your clay supplier for the sintering temperature of your clay.

We have some glazes in our program that should run (see pictograms in the catalogue), so please only glaze the lower area of ​​your object very thinly. But if other glazes run off, it could be because the application was too thick or because the temperature was too high. You may want to check the oven temperature actually reached using Seger cones (or Orton cones). We recommend protecting the oven plates with a release agent (e.g. BOTZ release agent item no. 90108).