Sodium Silicate 140tW 25kg

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• Sodium Silicate Na2SiO2 is the most popular deflocculant used in casting slips, and has been so for many years.
• It is nearly always used with soda ash - when used alone it can make a slip stringy and thixotropic.
• It is effective, reliable and inexpensive but attacks the plaster in moulds much more than more modern deflocculants and it is easier to over-deflocculate a slip with sodium silicate.
• Sodium dispex (345921) is a possible alternative which avoids problems of brittle and soft casts associated with sodium silicate and soda ash.
• As long as Sodium Silicate is not allowed to dry out, the shelf life is indefinite. If it does dry out and crystallises it can be redispersed in hot water but the dilution will need to be adjusted by trial and error.

Which "Twaddle"?

A degree Twaddle (∩┐╜Tw) is a unit measuring the specific gravity of liquids denser than water. 1 degree Twaddle represents a difference in specific gravity of 0.005 or 1/200. The difference between the grades is the concentration of sodium silicate: 75Tw (346011) is like thin water and 140TW (346021) is similar consistency to treacle. Your recipe should specify which Twaddle to use but if it doesn't a general rule of thumb is 75Tw with Bone China and Terracotta (including terra sigillata), 140Tw with everything else. 140Tw differs in chemical composition to 75Tw so it cannot be 'watered down' and used as a direct replacement. 140TW can be thinned by gently warming to aid addition to slip.

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