Randy McCall on tue 19 oct 10
Here is a response that I got from Robert Harris that he shared with me abo=
=3D
ut Chrome Reds. I found it extremely helpful and thought it should also be=
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share with ClayArt.
To expand on John's post - it turns them green if you don't
simultaneously increase the Tin Oxide. By increasing both the chrome
and tin a more intense shade (or more saturated at any rate) colour
will be produced. By altering the ratio of chrome to tin you will
alter the colour. Less chrome=3D2C more tin will be pinker=3D2C more chrom=
e
less tin will be mare maroon (at least that's what I'd call it). As a
general rule of thumb you want the chrome:tin ratio to be between
about 1:10 to 1:20. YMMV. Obviously base glaze is also tremendously
important.
It occurred to me that I also should have mentioned
that a good starting point for chrome:tin pinks is in the range of
0.25 - 0.5% chrome and the corresponding amount (2.5-10%) of tin. If
you're going to do a line blend I wouldn't bother going above 0.7%
chrome. For a real "pink" you would want to be on the low end of the
chrome and the high end of the tin. For a deep dark red=3D2C pick the
other end of the spectrum. I would hasten to add that these deep reds
can almost turn brownish - if this is a problem you might want to
think about changing the base glaze.
=3D20
In addition=3D2C the tin is still going to do its job as an opacifier=3D2C =
so
the light pinks are always going to be opaque. The deep reds don't
have quite as much problem=3D2C but in general are not "translucent"
either.
=3D20
The other thing to mention is that chrome is notoriously unstable at
higher temperatures and volatilizes off the pot. If you're firing at
cone 10 you will often lose the pink completely. Even at cone 6=3D2C if
you use tin in any of your whites you will be prone to get pink
flashes=3D2C especially if their on the same shelf.
Thanks to Robert Harris
=3D
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