Iron Oxide- Yellow (50# Bag)

This is one of the many raw colors of iron oxide powder. It is an iron hydroxide. Yellow ochre clay contains yellow iron oxide. In ceramics, red iron oxide is most commonly used in glazes and clay bodies, but black is also used. Yellow is the least color-stable form. Yellow iron oxide is a synthetic material of very fine particle size (but not as fine as black or red). All forms of iron normally produce red coloration when fired in clay bodies in oxidation.

Actual yellow iron oxides are around 85% Fe₂O₃ and about 12% LOI with some impurities (e.g. SiO₂, CaO).

Theoretically, any form of iron could be used to source Fe in the fired ceramic product (of course they lose different amounts of volatiles on firing so they cannot be substituted gram-for-gram). However, in practice, this is not the case. Yellow iron, in our tests, for example, does not stain a glaze but it does stain a clay body. The reason is not apparent.

Yellow iron is not as fluffy and light as black, but more than red. It does not agglomerate as badly as red, but more than black. It is coarser in particle size and can leave some lighter colored residue on a 325 mesh screen (up to 8% in one specimen we tested whereas the others left zero).

Like other forms of iron, this is never used pure, it is always part of a recipe (a glaze, engobe or body).

Yellow iron is also used in paints, enamels, concrete colorants, plastics, rubber, and paper where permanent yellow is required. It has excellent hiding power, absorbs ultraviolet light, is compatible with a broad range of vehicles, disperses well in aqueous and solvent systems, and does not contain heavy metals.

One process of manufacture involves precipitation of ferric oxyhydroxide followed by purification through washing, drying and milling.