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Darvan #811 Soda Silica N Brand

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I made a trip to Standard for some supplies. I had to pick up some Darvan and Sodium silicate.

The lady in the store ask me why I was purchasing both, and she said they were exactly the same, just a different brand.

What are your thoughts?

I was thinking it was a little harder to over dose slip with Darvan. My recipe uses both.

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2 products that do similar things to clay/slip/glaze, but are chemically completely different. Sodium silicate is just that, Darvan 7 is a long chain polyacrylic acid. Whereas Darvan 811 is a short chain polymer, with a low molecular weight, less appropriate for glaze, more so for clay and slip. A polymer that you would probably not be able to recreate without an advanced chemistry degree and a lab.

My experience with them is that Darvan created a more stable slurry and is much less caustic to both you and mold hydrocal/plaster. However, as John says above, if you are applying it to stretch clay and get a cracked effect, Sodium Silicate is the one to use. Both are inexpensive and easy to purchase from any well stocked pottery supplier. If you are in Philadelphia, where Standard is, you can get Darvan at the Ceramic Shop which I believe is on on Amber Street. Or order online from the Ceramic Shop, Axner, Clay King, Bailey, etc.

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I would like to keep my molds in good shape as long as possible.

No Sodium carbonate when using Darvan, Darvan 7 sounds like the way to go for healthy molds.

 

Long chain, short chain...could you dumb that down

Why is the seven better than the 811?

 

Do you guys use Barium Carbonate in your slip?

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Long chain and short chain refers to the molecule length of the polymer. It reflects the molecular weight. I think the difference between the two is that Darvan 7 is appropriate for glaze and clay, whereas Darvan 811 is more appropriate for use with clay and slip. I only use Darvan 7, and really like the slip that I make when using it.

I learned the difference between the two when I was researching which one to use. One is not superior to the other, though I would say that for deflocculation they are both superior to Sodium silicate and soda ash, it just depends what you're using it for.

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