|Monthly Tech-Tip |
Modified: 2022-10-13 21:48:31
Cone 8-9 - Spodumene, talc variant
|Ferro Frit 3110||50.00|
From Crystal Glazes Book 1 by Fara Shimbo, page 141.
Maturing Cone: 8-9, though works well at 7 and even 6. Crystal number: Lots.
Rate Of Growth: 1-1.5 cm diameter per hour, tiles or vessels.
Crystal Color: Very, very white with much internal structure.
Crystal Shape: Much like hemimorphite, often with frilly ends.
Ground Color: Colorless transparent on both tiles and vessels.
Crazing: Minimal on vessels; more on tiles.
Color Response: Great, but crystals colored with copper are likely to be quite transparent. Manganese shares this effect to an extent.
Seeding properties: Very good.
So far, my favorite glaze for obtaining nickel-blue crystals on a transparent amber ground (via the addition of 3% nickel oxide). Generally fires from cones 8 to 9 but when nickel is used, otherwise to cone 10.
Due to low titania in this glaze, crystals colored with less than 4% copper carbonate are likely to be transparent and difficult to see.
One can get gorgeous dark steel blue crystals on a honey or amber colored ground. I developed Celestite from this glaze to have a glaze that was slightly higher in lithium than Base 5, specifically for use with copper turquoises.
Fa's Base 5 has more zinc and less silica than Celestite, and many people have reported to me good results firing this glaze as low as cone 5. Recommended firing is to take the kiln to temperature, hold five minutes at peak, then drop 50°C and start a slow ramp downwards to 1000°C over about an hour and a half. I've never done this myself but I've seen several beautiful pieces done this way.
A tile made with Fa’s Base 5 and 3% Nickel Oxide. Reduction does not affect this glaze very much. If anything, the colors will be slightly muted.
Fa's Number Five
Four-step to 2318F
Shimbo Crystal Celestite Schedule
Five-step schedule by Fara Shimbo
Crystalline Glaze Forum
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|By Tony Hansen|
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