Chris Schafale on fri 22 jan 99
Hi Ron and all,
Tested Ron's cone 6 black recipe. Here are my early results, though
I haven't done all the tests Ron recommends below.
1. Tested on Standard 112 (buff stoneware), Campbell's Warm
Brown stoneware, Campbell's Golden Tan stoneware. Fired in Skutt
1027 with controller, on Slow setting, to cone 5, with witness cone,
cone 5 just touching the shelf. Soaked 15 minutes at top
temperature. Did not measure time from red heat to cone half down.
Results: On all bodies, glaze appears inadequately melted. Surface
is gritty, slightly metallic, quite black. Some evidence of
cracks/incipient crawling
2. Same clays, same kiln. This time fired in an extended firing
(with my frustrating iron reds) with slowed heating and cooling
through the 700-900 C range. Soaked 30 minutes at 1185. Cone
response as above.
Results: Similar to above, but surface appeared slightly more
melted, smoother, crawling now more evident.
3. Tested on Highwater Red Rock (red-brown stoneware) and Campbell's
Red Brown stoneware. Same kiln. Fired on Slow setting to cone 6, 20
minute hold. Witness cones showed cone 5 completely flat, cone 6
just slightly short of full bend.
Results: Similar to #2, perhaps slightly smoother but still gritty
and appearing underfired. No crawling evident on these samples, but
glaze coat may have been thinner.
I haven't done the boil/freeze test yet -- figured I'd wait until I
got the thing to melt. At this point, no signs of crazing or
shivering.
OK, Ron, what next? Also, a question -- I confess I'm not certain
what you mean by "red heat" -- dull red? bright red? If you can
specify a temperature, that would be easier.
Chris
> ----------------------------Original message----------------------------
> Hi Jim,
>
> I am guessing you want it for cone 6 oxidation - if it's for reduction I
> will have to do it again.
>
> This first recipe is just the first of what will probably be several to get
> a stable, durable black at cone 6 oxidation - anyone who wants to do the
> tests will learn something about developing glazes for cone 6. All you have
> to do to get the next in the series is post the results to the list - fired
> with a cone beside it, what kind of clay - how long the firing from red
> heat to cone 6 half down, how long soaked, cone bend plus frozen and dipped
> in boiling water 3 times and report any fit problems.
>
>
> RR c6 black #1 sieve 2 times through 80 mesh. Should be good under and over
> other glazes but when layering - do some testing first to see if running is
> going to be a problem. Many of the glazes we are using are unbalanced and
> when they are melted with a balanced glaze they may over flux it.
>
> -----------------
> F4 SPAR...................22.00
> WHITING...................9.00
> TALC..........................2.00
> F3134........................21.00
> EPK............................17.00
> SILICA......................29.00
> RED IRON OX........10.00
> Cobalt Carb..............1.00
> ----------
> Total......................111.00
>
> FORMULA & ANALYSIS
> ------------------
> *CaO...............0.52.......9.43%
> *MgO..............0.05.......0.62%
> *K2O...............0.04......1.09%
> *Na2O............0.18......3.57%
> Fe2O3.............0.19......9.83%
> TIO2................0.00......0.05%
> *B2O3............0.21......4.69%
> AL2O3............0.32...10.37%
> SiO2...............3.14....60.32%
> P2O5..............0.00......0.02%
>
> RATIO 9.89 - Original ratio is 10.02
> EXPAN 464.53 - Original expansion (my scale) is 461.19
> WEIGHT 312.40
>
> If anyone needs it with a different spar and/or a different frit let me
> know which ones you have. Ferro frit 3124 is not good for this because it
> has too little boron and the alumina will limit the amount of raw clay in
> the bucket. Ferro 3278 or an equivalent will work well.
>
> Substitution frits for Ferro 3134 are: Pemco P-54, Hommel 14, Fusion F-12
> and GF 111.
>
> >----------------------------Original message----------------------------
> >Ron..please do us a favor and alter this glaze to fire at cone 6.. Thanks
>
> 3D Black - cone 10 reduction.
>
> Kona F-4 ........42.23
> Whiting...........11.52
> EPK................6.72
> Flint................32.63
> RIO.................6.14
> Cobalt Carb.....0.77
> ---------
> 100.01
>
>
> Ron Roy
> 93 Pegasus Trail
> Scarborough, Ontario
> Canada M1G 3N8
> Tel: 416-439-2621
> Fax: 416-438-7849
>
> Web page: http://digitalfire.com/education/people/ronroy.htm
>
>
Light One Candle Pottery
Fuquay-Varina, NC
candle@nuteknet.com
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