Produced from calcined mixtures of tin oxide, lime and chrome oxide in the form of potassium dichromate. Certain colours contain silica and small quantities of other compounds as modifiers.
Pale pink through crimson to maroon and lilac shades. Most chrome-tin based colours are bluish in comparison with manganese and iron-based colours.
Specific Gravity: 3.75 to 4.75
Excellent for firing in an oxidising atmosphere at temperatures up to 1250C.
Overfiring or firing under reducing conditions causes severe fading. Unstable in the presence of zinc oxide.
Suitable for blending with most types of zinc-free ceramic colours. The best color development can be had using glazes produced with high calcia frits (e.g. Ferro 3134).
Since these stains tend to be refractory, crawling of overlying glaze can sometimes happen where a 'dry' underglaze lacking sufficient flux prevents the glaze from gaining a foothold on the body underneath.
Relatively high owing to the relatively high intrinsic cost of tin oxide.
Note: This description is taken from information provided by Blythe Matthey and may or may not apply to stains of this family from other companies.
Best results are obtained with zinc-free lead-containing glazes having a high content of lime and a relatively low content of boron oxide. Care should be taken to prevent contamination of the glaze by metallic or organic dust particles, such as specks of iron or carborundum, which can produce local reducing conditions during firing, bleaching the area surrounding the particles, and resulting in white spots. Close inspection of this defect reveals the dust particle as a black core in the center of the white area. Risks of producing the defect are minimized by the use of lead-containing glazes; the higher the lead content the greater the solvent action of the glaze on the dust particle.
Underglaze Color: Excellent for use under most types of zinc-free or low zinc-content glazes for firing in an oxidizing atmosphere at temperatures up to 1250C.
Not generally used as engobe or body stains. However, special engobes having a high content of lime can be formulated for the production of crimson engobes. Even then, high additions of stain are necessary.
Out Bound Links