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Porcelain Enamel Firing Flaws

Porcelain enamels enamels firing enamels

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#1 john wood ceramics

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Posted 14 December 2013 - 04:05 PM

I am trying to paint enamels on my cone 6 porcelain with clear glaze. Every time I test fire the enamel crawls or beads in some spots or has a rough texture and in other places is fine or dull. I clean the surface with alcohol before painting and have tried firing at cones 018 , 015 and 014 all with the same results. Any suggestions would be appreciated. Thanks John



#2 JBaymore

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Posted 14 December 2013 - 05:31 PM

John,

 

Overglaze enamels (china paints) can be very "fussy". Application thickness is important for the fired surface qualities. If they are thin applications in the raw form... they do not change. In fact, they look pretty much the same after firing as they do before firing.  Too thick and they will crawl and or run.  Too thin and they tend to be dull and wispy and dry. 

 

We'll likely be able to help more here with a bit more info.

 

Are you using oil based medium or water based medium? Are you using dry paint or already wet mixed paint? Brands? Are you grinding them before application on glass or ceramic glazed plates?

 

Are you using brushes / applicators / containers that are used SOLELY for the china paints?

 

After your alcohol cleaning, is there any danger of finger oils or dust getting on the surfaces?

 

After the enamel is applied, are you protecting it from any geneal studio dust before firing?

 

What is the background glaze recipe/formula?

 

best,

 

.....................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#3 john wood ceramics

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Posted 15 December 2013 - 10:19 AM

Thanks John for your input. Some more technical info: The work is covered after cleaning with alcohol. I am using only enamel dedicated brushes and I am grinding dry enamel on a ceramic tile using water with a bit of gum Arabic as a medium. It is the inconsistency that is troubling . The same color areas next to each other. One is fine the other comes out as beads of glaze not a flat film of even glaze. The glaze I am using is Soda Spar 38,Whiting14, Zinc Oxide 12, OM4 6, Silica 30. The enamels are Josephine Porcelain Paints from Kathy Peterson. See two photos to show problems . Thanks John

 

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