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ficus.ceramica

Sodium silicate as a post-firing sealant

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I recently read that you can use sodium silicate as a post-firing sealant for raw clay, in the same way that it's used to seal concrete, as "water glass".  I use cone 6 porcelain, and I love leaving the bare clay as a design technique, but there's still a good chance that the exposed clay will stain with use - esp coffee and tea.  So I am going to try using it to protect against future staining after use, but I wonder if I put it on before the pots go into a luster firing (cone 018), will the sodium silicate molecules bond more completely with the clay body?  Will it eventually wear away with use?  It doesn't stand to reason that it would burn away, since it's not organic, but will it volatilize?  I can't find very much info on this specific use of sodium silicate, either, though I have discovered a mind-blowingly large amount of uses for it in all kinds of industries, as well as just ceramics.

 

Thanks!

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1 hour ago, ficus.ceramica said:

I use cone 6 porcelain, and I love leaving the bare clay as a design technique, but there's still a good chance that the exposed clay will stain with use - esp coffee and tea. 

Nope, it shouldn't stain if it's fired to vitrification. I've got some brown clay bowls and mugs that are in daily use, zero staining on the outside parts which I left unglazed. On a side note, if you do leave part of the pots unglazed and part glazed (inside) I would suggest really checking for a very good glaze fit so you don't have dunting issues.

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1 hour ago, ficus.ceramica said:

So I am going to try using it to protect against future staining after use, but I wonder if I put it on before the pots go into a luster firing (cone 018), will the sodium silicate molecules bond more completely with the clay body? 

Short answer:  Yes the “water glass” will react with the clay body.  

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