David Malicky on sat 1 jul 00
i'm experimenting w/ some cone 6 ox copper reds and am running across
some typical problems: pinholing and runniness. i'm using SiC for my
local reduction agent and am getting great reduction - virtually every
test has become red or purple w/ no black spots (its 1000M SiC from Rovin
Ceramics, 734-374-0010, no affiliation). but, the pinholes persist and
only get worse w/ more flux as the runniness increases, resulting in
pooling and longer bubble paths. i am assuming the pinholes are coming
from the CO2 released from the C of the SiC and the O of the CuCO3. good
assumption?
if so, are there other local reduction agents that will grab the O but not
form gas? some thoughts: powders of elemental Si, Fe, Al, Zn, or even Cu
itself. has anyone tried any of these? (the Si idea was mentioned by
digitalfire). i'm guessing its non-trivial as we want the reaction to
occur at cone 6 and not have the Si (e.g.) all consumed before we get
there, or not consumed at all. there's also toxicity and flamablilty (Al,
at least) concerns.
i've also heard bone ash helps absorb the gas, but i don't know how it
could do this as its already appears fully oxidized. any experience w/
this?
fyi, i'm typically using 0.3% CuCarb, 0.33% SiC, and 1.0% Sn. firing is
in a skutt kiln, the 'slow' cone 6 firing schedule (automated), regular
cooling.
also fyi, here's one of the better recipes i'm working on:
+++++++++++++++++++++++++++
+++ Sanders&LaDonna +++
+++++++++++++++++++++++++++
Kona F-4 29
Frit 3110 29
Gerstley borate 10
Wollastonite 3
Dolomite 3
Zinc oxide 3
EPK 3
Flint 20
Tin oxide 0.9
Copper carbonate 0.25
SiC 0.28
Na2O 0.31 Al2O3 0.25 SiO2 3.30
K2O 0.08 B2O3 0.27 SnO2 0.02
MgO 0.05
CaO 0.43
CuO 0.01
ZnO 0.12
Alumina:Silica ratio is 1.00 : 12.97
Neutral:Acid ratio is 1.00 : 6.36
Alkali:Neutral:Acid ratio is 1.00 : 0.52 : 3.32
thanks,
dave
----------------------------------------------------------
David Malicky
Mechanical Engineering Department
Valparaiso University
David.Malicky@valpo.edu
http://diamond.gem.valpo.edu/~dmalicky/
219-464-5062
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