what to do about devit on slumped dish

[gemhike]

I got devit on a plate which has been fired, then flipped and fired with clear frit, flipped and slumped.  The devit didn’t show up until the slump.  Anyone have suggestions for getting rid of it.  I want it to be food safe.

[Stephen Richard]

This is difficult.  Most methods of removing devit involve either a chemical and tack fuse temperatures, or abrasives and tack fuse temperatures.  So the heating reauires is above the slumping temperature. Although there are some preparations – bendiong glazes – that claim to give a shiny surface at slumping temperatures, I have never found them successful.

It is possible to sandblast (with fine grit) or abrade with 600 grit wet and dry sandpaper, to get rid of the devit.  You then need to use a low slumping temperature (ca. 620C) for a long soak (say 90 mins) to give a satin texture to the surface.

You could coat the surface with a borax solution, flatten it and take it to a tack fuse temp. and re-slump, but this depends on what will happen to the shape when you flatten it again.

Of course, as you now know prevention of devit is better than correction.  The glass needs to be thoroughly cleaned before and after each firing.  My approach is here:

http://glasstips.blogspot.co.uk/2010/08/cleaning-glass.html

Stephen Richard

blogs at: http://www.verrier-glass.blogspot.com/ and  http://www.glasstips.blogspot.com/

[Blackhillstudio]

I have a question about devitrification and I don’t even know if I have it. I am new here and very inexperienced. I am not sure if the proper way to ask another question on this topic is to post a reply or write the author.

my problem is that when I slump a clear glass tray in my mold the horizontal surfaces on the bottom are a bit frosty. I don’t know if this is because of the mold or it is devitrifying. I don’t mind it really, I just wondered if it is a fault that I should correct somehow. The top surface is fine. I am slumping to 1240 f., hold 30 minutes.

Thanks for any thougts,

Brenda

[Author]

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