Silicon Carbide (SiC) is an extremely hard nonoxide ceramic used in an array of thermally and mechanically demanding products, including abrasives and wear resistant materials as well as refractories. Due to its hardness, SiC finds use as an abrasive; wear resistance material; and as a refractory.
SiC is also widely utilized in crater and foam glazes. The carbon released by SiC particles acts to decrease metallic oxides like iron and copper oxides and facilitate color development during oxidation firings.
Lava or Crater Glazes
Lava glazes (also referred to as fat lava glazes) can add textural interest to your pottery pieces by way of beautiful silicon carbide powder craters in these glazes, creating dynamic visual textures. Their flexibility enables you to customize the look for each of your pieces.
Lava or crater glazes can be easily created by adding silica grit to copper earthenware glaze during its melt phase and firing it at cone 06 oxidation with a 20-minute hold time. For best results, coarse grit like 400 to 800 is best as this will avoid filling all glaze spaces completely and leaving razor sharp edges behind on your craters.
West German pottery makers made use of this technique during mid century. It proved an extension of Bauhaus design concepts, creating affordable decorative ceramics in tune with sixties art styles – particularly its use with space exploration themes like space ships or Sputnik shapes. Lava glaze surfaces provided the ideal surface to achieve this look!
Silicon carbide (SiC) is an extremely durable nonoxide ceramic that serves multiple purposes. Found naturally as the extremely rare mineral moissanite, SiC can also be made synthetically for use as abrasives and wear-resistant mechanical parts, in high temperature applications due to its low thermal expansion rates, excellent strength characteristics, as well as in electrical components for its conductivity properties.
Blistering Glazes
Silicon carbide powder creates the blistered surfaces seen in some so-called “crater glazes” by creating an air bubble effect, providing decorative ceramic art texture for decorative work. When adding this powder to a glaze recipe, however, its presence should be tested carefully to avoid too many bubbles breaking off and leaving sharp surfaces behind; should this happen, either more SiC powder may need to be reduced or the recipe changed altogether.
SiC particles containing carbon act as a reduction agent during oxidation firings of stoneware, helping reduce metallic oxides such as iron and copper oxides that would otherwise hinder color development in copper glazes. They are also helpful in producing reduction effects for celadons by lowering melting points of silica particles.
This glaze can be very fluid. To reduce its fluidity, using frit without alumina is beneficial; however, high ratios of CaO/Na2O to boron may also contribute. In hydrocarbon-fueled kilns this problem often manifests as uneven cooling. Testing for flow and lowering peak temperature to make glaze more viscous may help. A thinner glaze may even help with pinholing as less air pockets form into bare spots on pottery surface.
Foam Glazes
Foam ceramics are porous materials with uniform three-dimensional network structures that exhibit high porosity, low relative density and select permeability to liquid and gas media, providing outstanding thermal shock resistance, energy absorption capabilities, pressure resistance resistance as well as chemical functions and mechanical properties. Foam ceramics are widely utilized for applications relating to metal solution purification, casting metallurgy transport energy chemicals machinery national defense industries etc.
Silicon carbide (SiC) is used in ceramic glaze recipes as an effective means of producing bubbling, textured finishes in cone 6 oxidation firings. When heated up, SiC releases vapors which cause surface tension within the glaze to increase and bubbles to form; other ceramic glaze grits may achieve similar effects, however SiC remains by far the best choice if that’s what you’re after.
This work focuses on creating and characterizing various ceramic glazes containing SiC powder. These glazes are composed of combinations of industrial wastes, frits and commercial natural raw materials like float glass, granite and lime-shale (a byproduct from oil shale production in Sao Mateus do Sul, Parana). Results demonstrate that by choosing an optimal ratio between wastes and natural raw materials for production of glazes it is possible to obtain both transparent and opaque glazes with excellent chemical resistance, abrasion resistance hardness color coupling properties between porcelain stoneware tile supports.
Reduction Glazes
Reduced glazes produce toasty clay bodies and copper reds while oxidized ones create soothing celadons that display vibrant glaze chemistry. Different shutoff cones offer unique effects that give potters vibrant results that show off bold glaze chemistry; yet one type of firing cannot easily be replicated: reduction atmosphere that gives glazes their natural, unfinished appearance. Reducing is possible both gas and electric kilns but requires careful balance of ingredients in order to avoid shuddering glass or etching glaze surfaces.
Silicon carbide plays an essential part in this process by producing gases at the top end of a kiln that produce gases which create the effect of a volcano or volcanic crater on the glaze surface. This effect can be accomplished with just one easy recipe, and looks particularly striking on crystalline glazes.
Celadon glazes are one of the oldest color glazes in China and are traditionally fired under reduced conditions to achieve their elegant blue colors (see images here). We investigated their appearance, chromaticity and microstructure with or without SiC using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), producing blue structural colors from those using SiC compared with weaker amorphous coloring using tin oxide as an auxiliary reducing agent (see image here).