Robert Harris on sun 13 may 12
John =3DA0- and everyone else who is interested.
I actually completed my first round of testing about a week ago.
Unfortunately since my firing took an hour and a half longer than usual
and all my other glazes turned out weird I'm assuming that my elements
are in need of replacement (although none of them are actually broken
- they all glow appropriately, and they fired a bisque to 010
perfectly fine).
I did almost exactly what you said, added SiC to normal copper red
recipes. I used 6, 3 from your book, Pete's Red, Pete's Super Red
(which has Spodumene in it), and Tom Coleman's Vegas Red, plus two
other (different) Coleman Red recipes, and a sixth one that I derived
from an analysis of a Yongle red, by Nigel Wood.
Pete's Super Red, and the Vegas Red almost completely burnt out, only
hints of a reddish brown colour at the contours of the test tile.
The Yongle red was probably a bit stiffer than the others (no
Gerstley!), and with 0.15% SiC turned a weird mottled pink, it sort of
had a fractured
honeycomb pattern to the colouration (although the glaze was smooth),
but at 0.3% SiC I got lava effects.
Probably the most successful tests were Pete's Red and one of the Tom
Coleman recipes (from a 1979 Studio Potter issue). However they turned
the classic liver colour of a badly fired/reduced copper red.
Obviously I really need to redo the tests after I've replaced the
elements, but my guess is that the next stage of testing is to do a
proper line blend with SiC.
I would also note that all of my recipes were derived from Custer
rather than a true soda spar. In theory this should only affect the
hue of red rather than anything else, but as soon as it becomes
worthwhile for me to get a delivery from my supplier, I'll get a true
soda spar in to test. (Unfortunately my nearest pottery supply place
is 3 hours away).
As an aside, I have learnt a lot about grit sizes. Probably the best
information is here http://www.alphamaterials.com/grit_chart.htm.
In summary, there are a number of different grit standards and the
actual size (in microns) of the SiC can differ quite significantly
depending on which Standard is used (and which purification method is
used). The biggest take home message for me was the 1500 grit Japanese
stuff they sell for rock tumblers is coarser than 1200 grit in the US
or European standards.
So be careful when getting your SiC.
Robert
On Fri, May 11, 2012 at 7:52 PM, John Britt wr=
=3D
ote:
> There is a great article in Ceramic Review July /August 2010 on silicon
> carbide electric reds by Mike Bailey. =3DA0He lays it all out.
>
> Ed's Red cone 10
>
> 53 Soda Feldspar
> 17 Silica
> 15 Whiting
> =3DA06 =3DA0EPK
> =3DA04 =3DA0Talc
> =3DA05 =3DA0Zinc Oxide
>
> 0.5 Copper carbonate
> 0.3 Silicon Carbide F1200
> 1.0 Tin oxide
>
>
> He varied the firing temp, thickness, type of silicon carbide and tin. It=
=3D
is
> all there!
>
> I have not tried this but would probably just try some standard copper
> red recipes with SiC added. =3DA0(There is no Gerstley borate or frits in=
t=3D
he
> recipe above, which strikes me a weird??)
>
> John Britt Pottery
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