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PIGMENTS

Miscellaneous

• Family: None
• Region: None
• Mined At: Unspecified
• Raw Mineral: Yes
• Generic: No

Notes

(Richard Willis)

Pigments are coloring additives for clays and glazes. They are usually calcinated before use in order to burn off gases, corrosives, and physical water, affording more reliable and stronger colorants. Calcinating temperatures vary greatly for compositions formulated with clays and/or silicas, but around 650ºC is normally sufficient for metal oxides alone. The idea is to burn the pigment without melting it, and the higher the temperature of a pre-melt burning the better. Pigments are added to clay and g laze formulas in small percentages, very rarely exceeding 6% in either dry or molecular weights. For example, 0.5-4% of cobalt will turn most any glaze blue at any temperature. Since crude, uncalcinated, pigments weigh more than cooked ones their “correct” percentage will vary substantially. see pigmented wares in PART I
common metal oxides used as ceramic pigments see also colorants
chrome — Cr₂O₃ — yellows, greens, reds
cobalt — CoO — blues
copper — CuO — blues, greens, reds
iron — Fe₂O₃ — yellows, browns, reddish-browns, greens
manganese — MnO — browns, yellows, purples
nickel — NiO — browns, khakis, blues, metallic greys
vanadium — V₂O₃ — yellows, blues, greens
recipes
blues:
— “delft” minium 20, CoO 25, kaolin 55, calcinate at cone 9
— “oriental” minium 20, CoCO₃ 20, Al₂O₃ 70, quartz 6, calcinate at cone 9
— “Sèvres” Cornwall 80, CoO 20, calcinate at cone 04
— “delft” Al₂O₃ 40, CoPO₄ 30, calcinate at cone 04
greens:
— quartz 85, CrO 15, calcinate at cone 9
— CrO 85, NiO 10, Al₂O₃ 5, calcinate at cone 9
— kaolin 30, CuO 15, calcinate at cone 04
— silica 85, CuO 15, calcinate at cone 04
— kaolin 70, silica 24, NiO 6, calcinate at cone 04
— sod/pot feldspar 15, silica 15, ZnO 15, KNO₃ 10, boric acid 20, CrO 25, CoO 0.01%, calcinate at cone 9
yellows:
— min. 55, ZnO 25, K₂H₂Sb₂O₇, 4H₂O 20, calcinate at cone 04
— Pb(NO₃)₂ 73, Sb 33, NaCl 100, Al₂O₃ 13, calcinate at cone 04
— kaolin 15, ZnO 50, FeSO₄ 30, K₂Cr₂O₇ 5, calcinate at cone 04
blacks
— FeO 42, CrO 43, MnO 5, CoCO₃ 18, calcinate at cone 04
— FeO 40, CrO 40, CoO 10, kaolin 30, calcinate at cone 04
— FeO 44, CrO 44, MnO 10, CoO 2, calcinate at cone 9
— CrO 25, CoO 10, Al₂O₃ 25, FeO 30, MnO 15, calcinate at cone 9
— CoO 25, NiO 10, CrO 30, MnO 15, colcothar 25, calcinate at cone 04
reds:
— SnO 41, crete 28, silica 28, K₂Cr₂O₇ 3, calcinate at 9
— ZnO 40, kaolin 25, FeSO₄ 30, CrO 5, calcinate at cone 9
— Al₂O₃ 15, FeCr 21, CuCr 27, MnO 7, calcinate at cone 9
“China red”:
#1 — SnO 50, crete 25, K₂Cr₂ 3, calcinate at cone 04;
#2 — CrO 40, pot/sod feldspar 60, calcinate at cone 9 then mix with 20% kaolin then mill four hours
— recipe: 25 parts #1 and 75 parts #2: mix, then mill 4 hours

Authors

• Richard Willis (Owner)

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