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Commercial Underglazes at Cone 10

from: kstevens@ups.edu (Ken Stevens)
Received: Thu, 2 Feb 1995 17:12:13

[Editor's note: Print and view this with a monospaced font such as
Monaco or Courier to ensure that the columns line up properly.
Many of the new zirconium encapsulated colors (reds, oranges, yellows,
and greens) will also work well at cone 10.] TESTS OF DUNCAN UNDERGLAZES at cone 10 in Oxidation & Reduction The order is an Underglaze #, then the name, then the color. If there is just a number and a color, it means I bought it later and didn't walk over to the studio to paw through the boxes of underglaze that I have to get the name. Unfortunately, they keep discontinuing them and adding new ones, so some that were most interesting or unusual are gone. Light Orchid, for example. All tests have underglaze under CACW glaze The starred glazes (*) are colors that worked in reduction with the same glaze. NUMBER NAME OXIDATION REDUCTION (*) D801 White Very white D802 Ivory Flesh colored C101 ArcticWhite White C102 Ivory Pearl Ivory D803 Light Yellow Pale Yellow D804 Bright Yellow Bright Yellow D805 Gold Amber: partly dissolved C103 Lotus Yellow Gone C104 Princess Yellow Soft yellow C105 Sungold Yellow Yellow/green tinge C106 Harvest Gold Rust: partly dissolved C141 Light Yellow Brt light yellow C142 Canary Yellow Brt yellow C143 Yellow-Orange Yellow/gold tinge C171 Butterscotch Warm tan D806 Light Pink Clear light pink D807 Deep Pink Brt pink * D812 Flesh Pale: flesh pink D826 Peach Peachy pink * D827 Dusty Rose Fairly brt pink * C108 Miami Pink Brt pink * C109 Sunset Pink Palest pink C111 Dresden Flesh Gone C112 Light Flesh Light tan C152 Peach Pink-may bubble C169 Peaches 'n Cream Flesh C178 Pecos Pink Lilac pink * D808 Dutch Blue Pale blue D818 Icelandic Blue Light blue D819 Sky Blue Blue/turquoise tinge D829 Navy Blue Harsh dark blue D830 Cambridge Blue Flat medium blue D831 Summer Blue Flat light blue C131 Teal Blue Dark blue green * C134 Stardust Blue Pale blue C135 Lake Blue Medium blue C136 Marlin Blue Royal Blue C147 Delphinium Blue Medium blue-violet C154 Cobalt Navy Blue Very dark blue * C159 Bright Blue Clear royal blue * C163 Danish Blue Dark blue * D820 Teal Flat turquoise * D832 Dark Teal Tealy blue * C132 Fiesta Turquoise Turquoise C133 Turquoise Pale turquoise C148 Deep Turquoise Dark turquoise C161 Blue Green Flat turquoise C174 Kentucky Bluegrass Dark teal * *C179 Teal * *C180 Flat turquoise D810 Pea Green Mud D811 Forest Green Dark mud D821 Victorian Green Light green * D833 Bright Green Medium green * C126 Spring Green Light green-blue C127 Fern Green Mud C128 Everglade Green Mud C129 Forest Green Grey green C150 Medium Green Light green C153 Avacado Textured green C158 Bright Green Bright green * D813 Brown Milk chocolate D814 Walnut Brown Dark brown D823 Ginger Brown Rough tan D825 Mocha Cream Palest pink C115 Bamboo Brown Tan C116 Aztec Brown Tan C117 Walnut Brown Dark brown C120 Samoa Taupe Pale blue grey C155 Light Brown Pale amber C156 Medium Brown Tan C157 Darkest Brown Very dark brown C175 Pale peach D815 Grey Pale blue D816 Black Textured black * D824 Glacier Grey Pale blue C118 Cobalt Crystal Blk Black * C119 Charcoal Blue grey C!21 Temple Grey Grey blue C122 Moonstone Grey Grey C164 Ice Grey Gone C165 Black Charcoal *- C173 Cobblestone Greenish grey D817 Lavender Lilac * D828 Light Orchid Bright lilac * C137 Regency Purple Light blue C139 Orchid Light lilac C146 Purple Dark blue C160 Deep Purple Darker blue C176 Greyed blue C177 Pale blue C172 Plum Blossom Grey blue C138 Wisteria Light blue C140 Morocco Red Light maroon C144 Burnt Orange Rust C145 Indian Red Pale tan C151 Rose Light purple-pink C170 Apricot Preserves Light tan C181 Mottled black A few other underglazes were also tested. None worked in reduction, but the results were interesting, nevertheless. Artex Underglazes #29 Cherry Red Maroon #46 Melon Maroon #28 Royal Purple Purple Harrison Bell Underglaze #10.722 Deep Coral Red orange The glaze referred to above has the following formula: CACW Whiting 23.5 Silica 34.0 EPK 18.0 Custer Feldspar 24.5 All of the firings were to cone ten either in an electric kiln for the oxidation or a gas kiln for reduction with the glaze sent over the underglaze. Actually, they were glazed with three different glazes, but this set gave the best results. There were some interesting tests with chun clear (the version in Carlton's (Ball) book. We have used chun at times, but not routinely. It is a much more active glaze than the CACW, and there is sometimes considerable interaction between underglaze and chun. While CACW merely covers them, chun sometimes actively dissolves them and lends some nice visual texture. The third glaze tried did not work at all (a version of PV clear that I got from John Blough at Mt. Sac up near Pomona.) Here are the formulas of all three glazes: 1. CACW 2. PV Clear (from John Blough) Whiting 23.5 PV Clay 50 Silica 34.0 Gerstley Borate 50 EPK 18.0 Custer 24.5 3. Chun (F.C. Ball) Original #s Custer 42.6 144 EPK 14.8 5 Silica 26.6 90 Whiting 2.7 9 Gerstley Borate 8.9 30 Dolomite 8.9 30 Zinc Oxide 1.8 6 Barium Carbonate 4.4 15 Tin Oxide 2.7 9 Again, all are fired to cone 10 in both oxidation and reduction EXCEPT the tin was omitted in the Chun, as it was originally added to promote red by re-reducing copper that was oxidized during cooling (in gas reduction firing.) This glaze makes a great dark blue on porcelain when fired in oxidation with 1/2% cobalt oxide and 2 1/2% red iron. A little oxidation on cooling can get little platelets of tin coming out of solution that are colored sort of yellow-gold by iron oxide. Of course if it happens too much, or is cooled too quickly, none of this happens. Know thy kiln, is the watchword here. If you know a place that meets the conditions, it's worth trying for it! Now you probably have more information than you want. Save the wheat, chuck the chaff! Ken



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