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David Snair Crystalline Glazed Pots


Babs

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Babs:

I have seen Mr. Snairs work before; he actually reminds me of Derek Clarkson out of England. Peter Frolich out of Austria also does these types of crystals. Bill Powell from Australia also grows some mean crystals.. Diane Creber out of Canada wrote a book on crystalline glaze: she likewise likes long soak/ramp holds. Susan Bunzl from Germany....

 

Learning how to manipulate crystalline glaze is the toughest part; of a tough glaze to master. Those you show are cone 10 firings, with a primary ramp hold of 4 hours minimum. Glaze thickness is what is causing crystals to grow around the foot, and towards the bottom of the piece. Tiles typically have 0.50 grams of glaze per square inch, and vertical pieces run a minimum of 0.60 up to 0.90 grams per square inch. When the glaze pools, like it has on the one piece: a solid field of crystals will grow. In a typical cone 10 firing, roughly one third of the glaze ends up in the catcher; which is part of the calculation of the amount of glaze applied.The top piece he purposely left part of the upper piece thin in glaze application; creating the "bare" spot. The bottom piece he used the typically distribution of glaze. In glaze application: the upper 1/3rd of the piece receives 40% of the glaze, the middle third 30-35% of the glaze, and the bottom third 25%. You have to calculate glaze run when you apply the glaze.

 

I would also go as far as to say he is using Cerox 506 zinc: which was discontinued over a year ago. Cerox 506 was the only French processed zinc that could withstand a cone 10 firing: the other zincs would vaporize long before the peak hold. If you compare the crystals on pieces from Europe, to those made in America: you will see distinct differences in crystal size and field clarity. The silica and zinc sold in Europe is much purer, and a slightly different chemistry; which produces much cleaner, and larger crystals.

 

Nerd

Note: small additions of iron will produce a silver tint in the crystals, and small additions of magnesium will produce a gold tint.

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I put this up for those who have contacted me in PM, about possibly exploring crystalline glazes. ZNO is used to control size and population.

 

ZNO levels

 

Tile 1: 25% ZNO         Tile 2: 26% ZNO       Tile 3 27% ZNO (left side)  When you drop below 25%, crystal develop becomes seriously hindered. In the typical standard recipe of: 50% frit, 25% ZNO, and 25% silica: as you adjust the zinc, you make the balancing adjustment to the silica. Frit usually does not move unless glaze flow is being manipulated. Silica can be dropped down to 18%, without much hindrance in crystal development. Silica is adjusted to help resolve crazing issues.

 

Titanium Dioxide is the primary seeding agent:

 

Baby Blue

 
This B&W shows titanium in the nucleus of the crystals. As little as 0.25% can be used; but amounts are used to help control crystal population. Recipes with more than 2% typically involve compensating for TiO2 lost in glaze run-off. Recipes above 4% and upwards of 10% are used for opacity and colorant effects. Titanium is highly reactive when used in a 3rd reduction fire to convert color fields: producing a purple field. 
 
Nerd
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