Application
BOTZ brush-on glazes are primarily suitable for 2 – 3 layer brush application. Some colours require thicker or thinner application, please observe the tips on the label on the container. In principle you can also add 20 – 30 % water and immerse or spray
Batt wash
To protect against dripping glaze, batt wash, a kaolin mix is spread directly onto the kiln plate. BOTZ batt wash is already mixed ready for use.
Biscuit firing
The thoroughly dried clay is "biscuit-fired" in an initial firing process in order to harden it and degas it, so that the glazes can later melt out virtually bubble-free. At the same time, the biscuit ware remains porous in order to be able to draw in the glaze. For BOTZ glazes, we recommend biscuit firing at a minimum of 1000°C with a 10 min. HZ = soaking time.
Brush-on glaze
Glaze which has already been mixed as a liquid and is therefore ready for use. The binder also contains suspension agents, dispersion agents and low quantities of preservatives to maintain the glaze's spreadability and stability for a long time.
Cast blanks
These are pottery poured in plaster moulds and can be decorated using glazes or decorative colours.
Ceramics
Ceramics are said to be the oldest material known to mankind. Ceramics can be classified as a collective term for products consisting of anorganic raw materials such as clay and glazes in the different firing areas earthenware, stoneware and porcelain. We distinguish between coarse ceramics (e.g. bricks and structural ceramics) and fine ceramics (crockery and objets d'art)
Coefficient of expansion
The coefficient of expansion describes the expansion behaviour of a mass or a glaze and its contraction when cooling down during the final phase of firing. Abbreviated as AK or WAK = coefficient of heat expansion provided. High AK values indicate a large change in volume. BOTZ products have various normal WAK values.
Decorative colours
These are highly concentrated bonded pigments for fine decor. Specially prepared decorative colours are used for the under-glaze technique (on biscuit-fired ware with a transparent glaze finish), the in-glaze or majolica technique (on the unfired glaze) or the on-glaze technique (on a glaze which has already been fired plus decorative firing).
BOTZ Unidekor is universally suitable for all decorative techniques.
Earthenware
Is often also called stoneware and is ceramics made from coloured clays at a firing range of approx. 1020 – 1100°C. Terms and temperatures in ceramics are traditional and differ often from region to region
Earthenware
is traditionally low fired ceramics with at least one light biscuit ware component which is still porous and can intake water. Therefore it attracts mixed clay glazes. Glazing in the earthenware range of approx. 1020 – 1100°C should seal the biscuit ware partially, but its major function is decorative. Earthenware glazes are considerably more colourful and effective than stoneware glazes but do not have such a strong connection with the clay. BOTZ brush-on glazes also adhere to higher biscuit-fired earthenware.
Engobes
Coloured, liquid clay applied thinly to the leather hard clay and then either biscuit-fired and transparently overglazed or fired unglazed up to its end temperature using weld penetration. BOTZ engobes can be applied to all clay drying statuses.
Fireclay
Fireclay is added to clays to reduce shrinkage and provide the mass with better stability and is effective against distortion and crack formation. Both fine-grain and coarse fireclay exist. Rotating masses can normally be prepared for better processing without fireclay. Plate clays and raku clays can contain fireclay shares of 40% and more.
Firing auxiliaries
These are highly temperature-resistant materials in the form of blocks or supports as spacers for the various kiln plates or as carrier objects for ceramics such as tile stands or tripods.
Firing service
Specialised dealers for ceramics requirements and several potters provide a firing service. Prices are often calculated according to the weight of the ware and the firing temperature level.
Frost resistance
The clay and not the ceramics determine whether ceramics are frost-resistant. If it is so highly fired that it can no longer intake and water (= lower than approx. 2%), the clay is sintered and the ceramics frost resistant.
Glaze
Mixture of frits, raw materials, pigments, oxides and specks in order to achieve overcoating similar to glass at various temperatures when firing. Industry and trade glazes are predominantly in powder form, brush-on glazes are recommended for school and hobby applications.
Kiln control
Electrical kilns are mostly safely controlled using an electronic control unit which constantly measures and regulates the temperature in the kiln using a thermocouple (temperature sensor). Heating rates for various firing areas (ramps), the end temperature and soaking time can also be set. Gas and wood kilns are in-part still controlled manually. In the Anglo-American world, mechanically controlled kiln sitter kilns are still common.
Lead-free
Lead is added to glazes in order to reduce the melting point and generate certain effects. Lead intake is highly detrimental to human health and must be avoided at all costs. Stirring a lead glaze can cause lead dust, lead odours may occur during firing and light acids can release lead from a glaze which has already been fired. All BOTZ products are technically lead-free
Manganese dioxide
A raw material for manganese oxide which is used for black clays. This frequently results in bubble formation in glazes on black clays. The bubbles are reduced at higher biscuit firing temperatures. Today, black clays with manganese spinels are used to replace manganese dioxide. Here, the glazes melt out virtually bubble-free.
Plaster moulds
Auxiliaries for manufacturing ceramic vessels and objects by moulding or casting (hollow moulds and solid cast moulds). Plaster draws the moisture from the art clay, thus forming a wall.
Porcelain
Highly fired ceramics from approx. 1240 up to 1400°C, also called "white gold". It mainly consists of feldspar, quartz and kaolin and the typical characteristics of the porcelain are its sealing properties and high degree of hardness and transparency. BOTZ Unidekor can be used easily on purchased porcelain if glazed with 9106 and fired at 1080°C.
Raku
is a ceramic firing technique from Japan which is predominantly used outdoors. It describes a special type of clay and the manufacturing process and the consequentially resulting ceramics work. The ceramics are heated fast and the glowing object embedded in organic materials (e.g. wood chippings). Smoke and a reduction process for the glazes generate the typical Raku effects. BOTZ glazes for which this fascinating technique can be employed are marked with the small flame symbol in the catalogue.
Seger cones
These are temperature measurement sticks with a special chemical composition and a defined melting point. Today, they are predominantly produced by the company Orton. Seger cones can also be used in addition to the kiln's thermocouple for precise temperature checking for firing, as the sole temperature measurement equipment (observed through the inspection pipe) or for the mechanical inspection of kiln sitter kilns.
Shrinkage
Clays are subject to dry shrinkage and firing shrinkage, commonly described as total shrinkage. This is provided in percentage figures. In case of increasing temperatures, firing shrinkage is generally higher.
Sintering
Sintering biscuit ware means that melt components cause vitrification and therefore compaction of the biscuit ware, allowing the biscuit ware only to absorb low water quantities. A clay is seen as heavily sintered if its water absorption is lower than approx. 2% following firing.
Stoneware
Stoneware is a sub-area in ceramics relating to heavily sintered objects in the firing range of approx. 1200 – 1300°C. BOTZ stoneware glazes are highly suitable for manufacturing crockery and drinking vessels.
Water absorption
The water absorption of biscuit ware is provided in %. In case of water absorption capability of up to 2 %, it is referred to as dense (sintered) biscuit ware: required for dishwasher and microwave crockery as well as frost-free garden ceramics.