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I am not a safety expert, or a chemist. Do not use this site as a primary source for safety, chemistry or disposal information.



  • Ferrous Chloride - Wikipedia
  • Ferric Chloride - Wikipedia
  • Ferrous Glocunate
    • Ferrous Gluconate
    • This material is used in black olives to keep them black and make the color consistent.
    • It is soluble. Like other iron compounds it is poisonous.
    • Solubility data is hard to find. It appears to be very soluble in hot water. In ph neutral solutions it oxidizes. If what I read is interpreted correctly it is more soluble and less likely to oxidize in mild acids.
    • I have not tried it. I don't know of a good source in quantity although you can buy pills with small amounts in them.
    • 446.139 g/mol -
    • C12H22FeO14·2H2O or C12H22FeO14 -
  • | Iron Sulphate, Copperas
    • Upon exposure to air, it oxidizes to form a corrosive brown-yellow coating of basic ferric sulfate, which is an adduct of ferric oxide and ferric sulfate: 12 FeSO4 + 3 O2 → 4 Fe2(SO4)3 + 2 Fe2O3
    • Solubility Heptahydrate: 15.65 g/100 mL (0 °C), 20.5 g/100 mL (10 °C), 29.51 g/100 mL (25 °C), 39.89 g/100 mL (40.1 °C), 51.35 g/100 mL (54 °C)[4]
    • It can be taken out of solution by Slaked Lime (calcium hydroxide)
    • I have been using Copperas from a local plant nursery. It is cheap and relatively safe, don't eat it. It would be smart to wear gloves because it does not wash off well. It is not great though as it reacts with air and a bunch of the iron drops out of solution. It looks good on raw clay and looks great at times over shino. I have only used it over Archie Bray Shino, a Wirts-like recipe. I have enjoyed it on red clays and white clays from about cone 6 up.Like other solubles do not get it mixed into your glazes.

Because Copperas reacts with air I have been considering a full change to Iron Chloride (Ferric). I have some hesitancy because of its corrosive nature and it now occurs to me because of the chlorine. In a gas kiln there is ample H2O for reaction it seems, but I wonder about what happens in an electric with lots of chlorine. It seems like a potential hazard that I do not have a big enough understanding of. I am not very concerned about one or two pots, but a kiln full might be a problem. Copperas when fresh and allowing the solids to settle makes a wonderful colorant on American shinos. The Iron chloride reacts with sodium carbonate. Although different, my limited testing makes me think that I will enjoy this to. Iron Chloride also appears to react with calcium carbonate. When put over a calcium carbonate glaze it appears to not work like soluble colorants and move towards edges but distribute itself through the glaze. On raw clay the chloride seems to spread out nice. So far I have not seen it favor edges much, it seems to deposit evenly. I am searching for something that would work better

I also have been wondering about using waste Ferric Chloride solution from printmaking. It probably has lots of copper chloride in it. Anything that keeps the copper chloride out of the waste water is probably good. Ferric Chloride solution can be treated with sodium carbonate to drop the copper chloride out of solution as carbonate (I think).

I am not a safety expert, or a chemist. Do not use this site as a primary source for safety, chemistry or disposal information.

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Page last modified on February 04, 2019, at 11:37 AM