DARV
A deflocculant supplied ready-mixed as a liquid · A long-chain organic polymer rather than a small inorganic ion · A forgiving casting window, and a long set in the mould · Distinctly alkaline, which is the condition the polymer needs to work
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Darvan 7 is a deflocculant supplied ready-mixed as a liquid, a solution of a sodium polymethacrylate polymer in water. It lets a casting slip carry a high load of solids and still pour.
Darvan 7 keeps clay particles mutually repelled, so a slip can stay fluid at a solids loading it could not otherwise hold. A slip made with it is slow to thicken on standing, castware can sit in the mould a long while without cracking, and the plaster takes up very little of the polymer, so scrap will usually go back to slip on water alone. Casting bodies commonly take a fraction of a percent, measured against the dry weight of the body, and up to about one.
