An intense deep blue that can break to pinks and violets under certain conditions.
Cobalt Oxide is an inhalation hazard and dermal contact irritant.It can cause conjunctivitis-like symptoms, rhinitis (inflammation of the nasal membrane) and irritation of the skin if protective measures aren’t taken.If the dust or firing fumes are inhaled they can result in cobalt poisoning and symptoms that include coughing, weight loss, respiratory hypersensitivity, dyspnoea, diffuse nodular fibrosis, decreased lung function and goitre.It has a carcinogen rating of 2B (possible carcinogen in humans).
It is recommended that Cobalt Oxide not be used on functionalware as an oxide wash or in a glaze that may leech.High gloss glazes help in binding otherwise toxic minerals, but there are concerns that some glazes will allow significant amounts of leeching, particularly if used with anything acidic (for example, a bowl holding a citrus fruit salad – especially if the fruit is left sitting in it for any length of time).This comes down to the specific glaze recipe, so I can only advise you to research your glazes and be aware of any leeching concerns before using them yourself or selling them as functionalware.
Cobalt, if ingested, can cause abdominal pain, diarrhoea, nausea, vomiting and polycythemia.
Cobalt Oxide gives a stronger colour than Cobalt Carbonate but has larger, coarser particles which can cause a grainy mottled effect.The exact composition will vary depending on supplier, but generally Cobalt Oxide is on average 1.4x stronger than Cobalt Carbonate.
Alumina = Green Chrome and Copper = Blue/Green-Blue/Green Chrome and Manganese = Blue-Black/Black Barium = Blue-Green Manganese and Selenium = Yellow Manganese = Slate Blue/Purple Manganese and Iron = Strong Black Rutile = Mottled and textured Blues with streaks Magnesium and Tin = Pink/Lilac Magnesium = Blue-Violet/Blue mottled with Red/Purple (with precise temperature control)