Tom Buck on sat 26 aug 00
Halo Jim:
You ask about water content of glaze slurries (slops). As a guide,
for most recipes, not all, a dipping glaze slurry should exhibit a density
of 1.53-1.57 grams/millilitre. A brushing glaze should be denser, with a
density of 1.65-1.67 g/mL; and a spraying glaze should be more watery,
with a density of 1.42-1.45 g/mL.
Since many glaze recipes use feldspars and clays (ball, kaolin,
other), they will exhibit different viscosities according to proportions,
etc. Also, certain materials release charged ions to the water, and these
ions can bring about agglomeration of fine particles so the slurry seems
thicker and denser. Such materials include soda ash (Na+ ions), unwashed
woodash (Na+, K+ others), gerstley borate (Na+, Ca++), borax (Na+).
One should avoid adding more water to gel-like slurries; in fact,
such well suspended glaze mixes will coat a pot better and dry without
blemishes. However, you may need to bisque higher if there is considerable
soluble material in the recipe (to keep solubles out of the pores as much
as possible).
To find the density, tare a measuring cup, draw off 200 mL of well
stirred glaze slurry, and weigh same. for dipping, 305 - 315 grams would
be about right. and so on.
good glazing. bfn. peace. Tom.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
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