John Britt's Snowflake Crackle - The cone 6 oxidation glazes

[George Lewter]

John had a great article in the Nov. 2011 issue of Ceramics Monthly which was excerpted and republished on the Ceramic Arts Daily Website as "Crazy Beautiful Crazing: Uncovering the mysteries of Snowflake Crackle Glazes" Click Here to go to the online article. I contacted John Britt and he said it was OK to reprint the recipes here so our interested members can carry the conversation forward.

Here are the recipes.

Recipe Name:  Original Snowflake Crackle
Cone:  6/7     Color:  Translucent     Firing:  Oxidation     Surface:  Glossy

Amount     Ingredient

  4.26          Magnesium Carbonate

 89.36          Nepheline Syenite

  6.38          Ball Clay--Old Mine #4
100         Total

Additives

2.00          Bentonite 

The glazes seem to work best on dark brown bodies.  Use only small amounts of colorants, as a lot will kill the crazing.

 

Recipe Name:  Snowflake Crackle #4
Cone:  6/7     Color:  Translucent    Firing:  Oxidation     Surface:  Glossy

Amount     Ingredient

   7.86 Talc

   5.77 Ferro Frit 3124

 86.37 Nepheline Syenite

100 Total

Additives

   2.00 Bentonite

   0.20 Copper carbonate for Turquoise

 

Recipe Name:  Snowflake Crackle #8
Cone:  6/7     Color:  Translucent    Firing:  Oxidation     Surface:  Glossy

Amount     Ingredient

   3.94 Magnesium Carbonate

   7.41 Ferro Frit 3124

  82.74 Nepheline Syenite

   5.91 Ball Clay--Old Mine #4

100 Total

Additives

   2.00 Bentonite

   0.20 Copper carb for turquoise

   0.50 Superpax for white

   0.066 Cobalt carbonate for blue

   0.50 Degussa stain 239416 for yellow

   0.50 Red iron oxide for rust red

 

[Penny Berglund]

Thanks! I will keep testing. I will see what I can get in the broad area I call local and will post results. I think you are right about the clay. I was very careful with the bisque fire.

Norm Stuart said:

I can't guarantee we've tried Snowflake with all of these clays, but these are our combined clay orders over the past five years.

WC 371	Big Pot Clay 60 mesh sand
WC 373	Dark Brown Clay -- fine sand
WC 376	L.B. Blend Clay 60 mesh sand
WC 381	Big White Clay with grog & sand
WC 384	Dave's Porcelain
WC 398	WS-4 gray/white with fine sand
WC 429	RSMC Red Clay
WC 894	Half & Half SC
WC-353	Paper Clay Cone 10
WC-370	Amador Cone 10 - densifies nicely at Cone 6
WC-390	Laguna Red
WC-391	B-3 Brown Black
WC-395	Porcelain Five
WC-400	Morrocan Sand
WC-402	Half n Half - pinholes with Ferro 5301
WC-412	Stoney White - new
WC-423	Greystone - contains magnesium or zinc which turns some blue and green glazes brown
WC-436	B Mix 5 with Grog
WC-438	Red B-Mix with grog   Easy Dry
WC-841	Danish White Clay
WC-842	Danish White Clay -- fine sand
WC-851	52 Buff
WC-861	Haggi Porcelain
WC-866	Electric Brown
WC-886	B Mix with Grog Paper - extremely problematic blistering, order only WC-353

Penny Berglund said:

I will try another clay body. I will also ask my supplier what they think. I am getting good crackle even where it is thin which would mean I won't have to go so nuts with the thicker glaze layer.

Is there a Laguna clay body that has worked for you with this glaze? IMCO? I can get clay at Clay Art Center in Tacoma, and I will be in Seattle next week and can get the clay bodies that Seattle Pottery Supply makes up as well. Since I am in the gorge now, it is also possible to make a trip to Portland to try what Georgies makes up.

Penny

[Penny Berglund]

I contacted John Britt, and other than trying other clay bodies, he had no suggestions. I did find it interesting that the worst problems were on the outsides/undersides of the pieces. Any idea about why that would be?

Penny

[Norm Stuart]

Snowflake glazes, like high-magnesium crawl glazes, have a tendency to fall off ware before it's melted in places where gravity does not favor it remaining in place.

Fire a bowl upside-down and you'll most likely discover the snowflake glaze is fine on the outside of the bowl but the glaze coating is thin and spotty on the upside-down inside of the bowl.

I experience the same problem with two layer oil-spot glazes where you place a runny top coat over an iron-rich base glaze. But in this instance the runny top glaze slides off after it's melted. Gravity is one of those laws or something like that.

[Penny Berglund]

I will try this next test go round. It would make sense with the large bubbles I got at times. But it still doesn't explain the pinholes prevalent on the undersides of pieces that had an even glaze surface and no bubbled lava effects.

[JC]

About that Snowflake crackle #4, I used that on several clay bodies and found I got a much better, more predictable result by spraying it on rather than dipping. It tends to settle very quickly and the talc/nepheline combo tends to clump when dipped.

Very nice finish when sprayed though.