True Cone 10 Zinc Crystal glazes have fascinated potters for the last hundred years. One major advance, digital controllers, put Crystal glazes in reach of any potter. In this short article, I will outline the basics and give some recipes.
Clay: use a smooth, white clay for cone 10; such as New Mexico Clay' s Domestic, CK-mix, or any cone 10 porcelain. Try making plates or tiles at first, as crystal glazes are VERY runny*. If you wish to make a vase you must throw a little dish to fire your pot on; after bisquing, glue the dish and the vase together with alumina hydrate.
The glaze: After trying many different glazes, I recommend one based on Ferro Frit 3110. Herbert Sanders book on Glazes for Special Effects (sadly, out of print) lists this as Glaze #3.
Notice that this glaze is very high in Zinc and contains no Alumina. The excessive amount of Zinc crystallizes into Zinc Orthosilicate crystals in the glaze, the same way sugar when super saturated in water will turn into rock candy. Low alumina allows the necessary fluidity* that the crystals need to be able to grow.
For color add these oxides to base glaze:
Cobalt Carbonate .75% to 1% for dark blue crystals with a lighter background.
Iron Oxide 4% for brown crystals.
Nickel Oxide Green 4% for blue green crystals on brown background.
Manganese Dioxide 1% to 4% for lavender on tan.
Uranium Oxide 6% to 10% for yellows and golds.
Praseodymium Oxide for white with yellow edges.
Apply the glaze by spraying onto bisque, as it contains no clay and is horrible to brush on. Try layering the glazes, as opposed to mixing the oxides, for interesting varied colors.
Firing: In general fire to cone 10, cool the kiln to 2000 degrees and hold for 3 to 5 hours in-between 2000 and 1800 degrees.
With a digital kiln a firing would go like this:
Ramp 1: rate 250°, to 1000° no hold.
Ramp 2: rate 500°, to 2320° hold 15 minutes. (00.15)
Ramp 3: rate 500° (to 9999 to cool faster), to 2000° hold for 03.00 hours.
Ramp 4: rate 500°, to 1800° hold for 01.00 hours.
Let cool, no peeking!
*These glazes are very runny. A catch plate is a base you throw that matches the bottom of the pot, it is then glued onto the bottom of the pot with a mixture of alumina hydrate and elmers glue. After firing the catch plate is removed and the bottom is ground to a nice finish. That is why I just made plates and bowls, not vases.
The Sandia Mountains - Plate by Brant Palley Cone 10 crystal glazes 1988
Regular Price: $20.00
Sale Price $17.00 Per Pint
A glossy pale green glaze like the melon it’s named for. Breaks across textured surfaces and develops a peachy float when thick. Great for layering with other glazes as a base or top coat. Beautiful on any color of clay. Good at cone 5, more fluid a
On a previously fired glaze surface paint as you would watercolors.
Clean up with water. Fire to cone 017 1400F
Includes 4 strips of 6-colors
Concentrated on-glaze color pigments, firing temperature 750-850 degrees C
No grinding required, just apply with a brush or pen
Open the cover to use, can be used for DIY ceramic painting.
Regular Price: $10,745.00
Sale Price $9,133.25 Per Kiln
POWER - DURABILITY - EASE.
1 kiln in stock today!
The Skutt Oval was designed with 3 main objectives in mind: make it powerful
enough to handle heavy loads (18.5 cu. ft. that's as much room as two 1027's
and a 1018 kiln! ) Make it durable enough to withstand the rigorous
demands of high volume production and make it easy to operate and maintain.
Powerful - At
23,600 Watts the KM1627 Oval is one of the most powerful kilns on the market
giving you the freedom to fire as fast or slow as you want to Cone 10
Durability - Due to
their enormous spans oval kilns have a history of cracking lids and slabs. Skutt
solved this problem by introducing the first fiber lid oval kiln with a fiber
insert in the base. The electrical components and wiring are industrial quality
to minimize downtime and boost performance. NOW FEATURES SOLID STATE RELAYS.
Ease - The light
fiber lid coupled with our innovative lid brace design make opening and closing
the kiln a one handed operation. The touchpad has been moved higher for easy
access to programming. Like all Skutt kilns the new ovals are sectional making
them easy to move, repair and disassemble for loading large pieces. The entire
kiln can be assembled and disassembled in less then 10 minutes using only a
screwdriver. Our new busbar element connection design makes changing elements a
Regular Price:$0.69$0.69 Per Pound
The clay is smooth, softer and because it has a little texture easier to work with . It looks like porcelain in the bag and after throwing it has just a hint of texture.
It is our most popular clay with schools and teachers because it is very soft and easy to use. It is excellent for all types of modeling projects and compatible with all MAYCO glazes.
FIRE TO CONE 04 BISQUE, O6 GLAZE FOR BEST RESULTS.
Now with Hydrated Magnesium Silicate !