Silicon carbide is a tough and resilient ceramic material. It has long been utilized in corrosion-resistant containers and pipelines in the petrochemical industry. Furthermore, silicon carbide is widely used as an abrasive in grinding wheels, cutting tools, and water jet cutters; in addition, its combination of high hardness, rigidity, and low thermal expansion make it an indispensable refractory material.
Crater & Foam Glazes
Crater glazes offer cone 6 oxidation an exciting textural option with their bubbly textures. Silicon carbide adds depth by taking up oxygen in the melt and combining it with carbon to form gases of decomposition that form bubbles in the glaze surface. Since there are various sizes of silicon carbide grits, it is crucial that they match up perfectly with your intended glaze texture; otherwise it will produce unwanted craters on its surface.
Plaster-based materials (like plaster ) can act as a potency source of bubbles in ceramic glazes, contributing to their discoloration.
This chemical chemistry includes high amounts of boron and zinc which makes it highly fluid, but its high level of inertness (LOI) also produces significant gases of decomposition which when released at the wrong time create a perfect storm of conditions that could lead to blisters. A drop and soak firing schedule could help alleviate this issue.
This chart compares the loss on ignition of six commonly used raw materials used to make ceramic glazes. It serves as a useful reminder that certain materials exhibit early melting characteristics while others tend to gasser more slowly – this may cause issues in glazes as early melters can overlap with late gassers and trap bubbles, potentially leading to blisters, crawling, pinholes etc. Switching out for low LOI ball clays may help alleviate some issues associated with such glazes.
Lava Glazes
Silicon carbide ceramic is an extremely hard, nonoxide material commonly employed in thermally and mechanically demanding products due to its superior heat resistance, low expansion rate and strength characteristics. Silicon carbide can be found in applications including abrasives and wear resistant materials; its hardness also lends itself to use in refractories for hardness. Crater glazes may utilize it due to its ability to decrease metallic oxides during oxidation firings while simultaneously aiding color development during color firing processes.
“Lava” or “fat lava” glaze recipes in ceramics usually refer to thick lava-like finishes, which feature vibrant colors as well as textural qualities in high cone 6 oxidation firings. Silicon carbide as a grit in these glazes is most effective at producing this effect; other grits may produce similar results but won’t do it as efficiently as SiC.
Lava glazes are ideal for adding texture to ware, as they can be applied easily by brush. Color Strokes or other designs will dry matt unless using CSP01 Gloss Medium; for best results fire to cone 06. Lava glazes should also be fired slowly at lower temperatures to prevent over-bubbling of their surfaces during firing.
Reduction Glazes
Silicon carbide powder creates the blistered surfaces seen in some “crater” glaze recipes and can add unique textures to sculpture ceramic art. These effects can be achieved either via oxidation or reduction firings (though reduction requires clay body reduction to avoid gas bubbles in the finished work), with carbon from SiC particles acting as a reduction agent during an oxidation firing and helping reduce metallic oxides such as iron and copper oxides – an effect especially helpful when copper glazes are fired under reduced conditions for jin opalescence when copper glazes are fired under reduced conditions!
Celadon glazes are traditionally fired under reduced conditions to achieve their striking blue colors, and X-ray photoelectron spectroscopy and scanning electron microscopy have revealed that the addition of tin oxide and silicon carbide as auxiliary reductants may help ease some of the stringent requirements necessary for celadon coloring. However, excessive use can increase redox reactions which leads to porosity and dark carbon deposits on glaze surfaces resulting in porosity or dark carbon deposits on surfaces.
Tested on celadons with various concentrations of tin oxide and silicon carbide, adding reductants significantly altered brightness values of glazes with stronger structural colors such as blue-green hues. When tested without such reductants present, yellowish-green hues dominated; their presence assisted in creating stronger structural colors while simultaneously increasing transparency.
Glaze Texture
Silicon carbide can also be used to craft lava glazes that add textural interest to pottery pieces, often combined with other frits to produce varied textures. Lava glazes tend to bubble and blister easily but still make great textural surfaces for decorative tiles or bases on sculpture pieces.
Glaze chemistry may appear complex at first glance, but is actually quite straightforward. Traditional ceramic base glazes all contain similar compounds; understanding their basic chemistry is key to understanding glaze physics and solving issues such as crazing, blistering, pinholing, gelling, settling, clouding, leaching leaching crawling scratching or color loss.
Boron blue, caused by low levels of alumina oxide content in glazes (alumina is the hardest oxide in glass), can be avoided by altering your recipe with different components – either changing from kaolin to calcined alumina – chemically equivalent yet their particle physics are vastly different; or substituting different frits for one oxide with equal chemical formula but unique particle distribution characteristics within the melt – something which necessitates looking at glazes as collections of particles rather than simply recipes!