C10R TEST TILES

GROUP 3

****NOTE:   Many raw materials used in ceramics are toxic and one should thoroughly acquaint themselves with these materials and their proper handling.  Some glazes, such as those with high barium and high copper content, for example, or other high concentrations of oxides, should not be used for items intended for food, or even anything that someone might inadvertently be able to use to store or serve food. Many glazes may be lacking in their base formulation, the minimum amounts of silica and/or alumina to properly hold the oxides in solution, making for a glaze that may be potentially unstable and potentially harmful when used to serve or store food or liquids.

I highly recommend that functional potters particularly, have their glazes tested for leaching of any potentially toxic materials. The lab at  Alfred University does now for a very reasonable fee (about $15 per test).  You can find information on this in the Clayart archives (see my Links page for a link), or write or call Alfred University directly.

RECIPES

Top row, far left tile is June Perry's Raspberry Copper Red  # 7009 A color on Windsor porcelain. It appears that  this my be able to take a bit more heat -- C 11 starting or even a bit more.

57.87 Custer Feldspar

21.35 Silica

A color, ADD: Copper Carbonate 1%, Tin Oxide 1%, Red Iron Oxide 1%

Top row, second tile from left is June Perry's  #6954 Copper Red on Tom Turner porcelain. This is lighter than the one to the left of it and as you can see.  Combining this glaze and the #7009 raspberry would probably give a good glaze. If anyone tries it, please let me know of your results. I've added the 2% bentonite or macaloid, and 1% more silica to the original. It should not affect the color but the extra tiny bit bentonite or macaloid  may help the application.

  .89 Magnesium carbonate

ADD: Copper Carbonate 1% , Tin oxide 2%, bentonite or macaloid 2%

ADD: Bentonite or Macaloid 2%

Color D, ADD: Copper Carbonate 0.25%, Rutile 1.5%

You can try other versions using other Ferro or similar frits like #3191, #3278, etc.)

Second row from the top, far left tile is June Perry Oribe  # 6695 on Windsor Porcelain. This is not a glaze for functional ware because of the high percentage of copper oxide, which would probably leach out into food. Keep this one strictly for sculptural or decorative pieces, or lower the Copper oxide to 3-4 % and have it tests for copper leaching. The expansion on this is low (6.17), and may not work on some bodies. I've created a second version (see below) to raise the expansion a hair . Version 2 on the right which has a less alumina and silica but still keeps the base within C 10 limits . It has not been tested, so if you test it, any feedback would be appreciated.

                                                                           Version 2 for bit higher expansion of 6.3 Ratio 8.25 (Totals 94)

22.41   Custer Feldspar                                      23.00 Custer Feldspar

33.85  Silica                                                        31.00

ADD: Copper Oxide 5.2%

NOTE: Version 2, untested has EPK lowered to 11 and Silica lowered to 30.  It is still within C10 limits.  

Second row from top, second tile from left is June Perry's Matt Copper #2481 Color D on porcelain clay body. As shown, this glaze is too low in silica and  is definitely not a glaze to use on food, even with extra silica added. It's too high in barium and Copper as well. If you want it to be within C 10 silica limits you need to add 20 more grams of silica. That would still keep it in the matt range. You can also try  substituting the barium sulphate with strontium carbonate, and lower the copper oxide to  3.5-4% Copper oxide for a lighter green. With the lower copper and the strontium substitution and the 20 grams extra  silica, it might be OK for functional work, but should be tested. This glaze is really intended for sculptural, non functional pieces like the outside of decorative jars, vases,etc.

 9.16 Lepidolite

 1.55 Zinc Oxide

Color D, ADD: 8.5 % Copper Oxide

Second row from  the top, third tile from left is June Perry's Mashiko Kaki #2478 Notice that the right side which has a porcelain engobe, the glaze is lighter and more red. The clay body is either Amador or Rod's Body. I've listed a B version for Temmoku. I think this is my version of a Mashiko Kaki from  the book "Oriental Glazes"   

52.17 Cornwall Stone

 5.80 Red Iron Oxide

B Color (For Temmoku) add 10% wood ash.

Second row from the top, far right tile is #2501 Kaki. This is a very beautiful Kaki glaze -- lovely surface and excellent, bright color. The clay body is either Amador or Rod's body. This is a good glaze to use over a clear or light celadon glaze that has had some wax resist stamping or brushing. 

 6.15 Talc

 9.23 Silica

ADD: Red Iron Oxide 6.15%

Third row from the top, far left tile is # 192  C 9-10 Ash glaze on an iron bearing stoneware.

40 Wood Ash

60 Albany Slip Clay

ADD: 5% Red Iron Oxide.

Third row from the top, second tile from the left is also #192 ash glaze (see above for recipe) on a porcelain clay body.

Third row from the top, third tile from the left and far right tile are both  # 3393 is a C9-10 Staley Ash glaze  on Windsor Porcelain.  The darker of the two was fired in a soda/salt firing and the lighter was fired in a regular C10 reduction  gas firing.

50 Albany Slip Clay

 5 Yellow Ochre

Bottom row, far left tile is # 215 C10 Oxidation or Reduction , is J. Bobbs Matt Black one an iron bearing stoneware. This is a lovely  Satin to Semi Gloss black. This glaze is way out of C10 limits. It's too high in KnaO, too low in Alumina and a hair over the silica limit. I would not use it on functional ware meant for food serving or storage; but it would be a nice glaze for the outside of vases, jars, boxes and other decorative pieces.

55.85 Potash Feldspar (I used Kingman but Custer or G-200 should work OK)

15.26 Kaolin

ADD: 2.22% Cobalt oxide, 2.54 Red Iron Oxide

Bottom row, second tile from left is #119  Black Albany slip glaze on a porcelain clay body. This is another beautiful black.  Like many glazes from the 70's this one is out of cone 10 limits. The alumina is in the .7 + range, and the Insight software (my older version) gives the maximum alumina as  .55.  It may be OK because of the high iron content, but always be safe and have glazes tested. 0251

85 Albany Slip (you might try subbing Alberta Slip. If it's not black enough try adding  1-2% more iron)

15 Nepheline Syenite

ADD: Bentonite 2%

Bottom row, third tile from the left is  June Perry's celadon #6924 Color A on Tom Coleman porcelain.  I  used a Craig Martell celadon, which crazed in my tests, as a starting point for this glaze.  As is, I use it as a liner glaze; but you can easily darken the color by the addition a 1/2-1% more iron oxide.  Ratio is 8.1 Expansion is 6.67 This base is within C10 limits.

29.9 G200 Feldspar (can use Custer)

31.69 Silica (I used Amorphous silica, but it may not be necessary )

ADD: Macaloid 1%

Color A: 0.5% Black Iron Oxide 2% Tin

Color B: (for deeper color) 5% Alberta Slip clay, 3% Tin oxide

Bottom row, far right tile is #305 Revised D color on Sasuga Porcelain. The blue line on the upper half of the tile is the result of a single, horizontal brushstroke of cobalt that I applied over the glaze. This is supposed to me a matt glaze and it is definitely not matt! It is a little low in silica and to bring it up to the minimum C10 silica limit, you should add 8 more grams of silica. It will still be in the matt range. All the other ingredients are within C10 limits. There is a bit of crazing on the tile and a bit of running, so the additional silica may solve that problem as well.

62.8  Custer Feldspar (original called for Kingman, but color was warmer with Custer)           

 8.0 Silica

ADD: 5% Rutile

NOTE:  Please feel free to write with questions or feedback on your test results with any of these recipes.                   June Perry

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