Ivor and Olive Lewis on tue 28 feb 06
Dear Sylvia Shirley=20
You say....."I do have a book on crystallines, but most of the recipes =
are
for cone 9/10. Does adding 5 percent lithium really work to lower the
temperature without ruining the effects of glaze? I checked the
archives and found a little information, but no recipes".
The lowest Eutectic fusion point in the ZnO-Al2O3-SiO2 System is 1305 =
deg C . That in the ZnO-SiO2 system is about 1470 deg. This goes, in =
some way, to explain the need to fire in the Cone plus 9 region.
If by "Lithium" you mean Lithium Oxide the answer would be "No" (mp =
>1700 deg C)though one of the Lithium bearing minerals (Spodumene, =
Lepidolite or Petalite) might assist, as would Lithium Carbonate with a =
melting point of 723 deg C. But used in anything more that a minute =
fraction that compound can lead to other problems .
By thinking of Zinc Crystalline glazes as being a two component systems =
(The ingredients for the crystals and the ingredients for the glaze =
proper) I have come to the following conclusion.
It is not always explained it books on this topic that the basic glaze, =
used for Zinc Macro Crystalline, decoration needs to have a vigorous =
solvent action to dissolve those ingredients which contribute to the =
growth of Willemite Crystals, that is Zinc Oxide with a melting point of =
1975 deg C and Silica mp 1610 deg C. Lowering the maturity temperature =
of the basic glaze decreases that components ability to dissolve those =
two alien ingredients.
Given the lack of information there seems to be an opening for some =
serious research in this field, though the answer might be to allow a =
longer time at Cone 6 to increase the thermal work done on those more =
traditional recipe ingredients.
No doubt we will get some alternative views.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
William & Susan Schran User on tue 28 feb 06
On 2/27/06 7:52 PM, "Ivor and Olive Lewis" wrote:
> The lowest Eutectic fusion point in the ZnO-Al2O3-SiO2 System is 1305 deg C .
> That in the ZnO-SiO2 system is about 1470 deg. This goes, in some way, to
> explain the need to fire in the Cone plus 9 region.
>
> If by "Lithium" you mean Lithium Oxide the answer would be "No" (mp >1700 deg
> C)though one of the Lithium bearing minerals (Spodumene, Lepidolite or
> Petalite) might assist, as would Lithium Carbonate with a melting point of 723
> deg C. But used in anything more that a minute fraction that compound can lead
> to other problems .
Ivor, hhhmmmmm..... I've been doing crystalline glazes at cone 6 for several
years. I've taught three classes over time involving the process. I have
several students currently doing a supervised study research on this
subject. I sent Sylvia some recipes and firing schedules to try.
Are the crystal formations that same as ^9/10 firing. No. Similar shaped
crystals are formed and some shapes not achieved at ^10 are possible at ^6.
I have started with several ^10 glaze recipes, added 5% lithium and had them
respond very well in a ^6 firing.
Hold temperatures for crystal growth is lower for ^6 than ^10 glazes,
but hold times are similar.
I fire very fast to ^6, usually about 4 hours!
I start the kiln on high!
No hold time at ^6.
Most of my ^6 glazes are composed, at a minimum, of 50% Frit,
usually Ferro Frit 3110.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Ivor and Olive Lewis on wed 1 mar 06
Dear Bill,
Nothing in this game is set in concrete. Opportunity beckons.
I take it the remainder of your Cone 6 recipes is a stoichiometric =
combination of Zinc Oxide and Fine Silica to guarantee the growth of =
Willemite Crystals. And that by Lithium you do not mean the element, but =
one of the many compounds of that element.
May well be that Ferro 3110 has an aggressive solvent action towards =
refractory compounds.
Whatever your recipes I really like your use of coloured backgrounds. =
They bring the crystals into prominent contrast.
Best regards,
Ivor.
William & Susan Schran User on thu 2 mar 06
On 3/1/06 2:23 AM, "Ivor and Olive Lewis" wrote:
> I take it the remainder of your Cone 6 recipes is a stoichiometric combin=
ation
> of Zinc Oxide and Fine Silica to guarantee the growth of Willemite Crysta=
ls.
> And that by Lithium you do not mean the element, but one of the many comp=
ounds
> of that element.
>=20
> May well be that Ferro 3110 has an aggressive solvent action towards
> refractory compounds.
>=20
> Whatever your recipes I really like your use of coloured backgrounds. The=
y
> bring the crystals into prominent contrast.
Ivor,
This is a FYI to add to your knowledge base and perhaps a response which
some sage advice on how you believe this recipe could be improved to produc=
e
better and larger crystals.
The original recipe came from Dan Turnidge. We have fiddled with additional
"crystal enhancers" and have changed the percentage of lithium, continually
altering to see what might happen. We have also varied the percentage ratio=
s
of zinc & silica, but the simple original seems to work best.
^6 Turnidge/MFE crystalline glaze
Ferro Frit 3110 - 50%
Zinc Oxide - 22.5%
Silica - 22.5%
Lithium Carbonate - 5%
Fired to ^6 in 4 to 6 hours.
Kiln turned off, temperature drop to 1000=B0C - 1040=B0C
Held at that range for 4 hours.
Kiln turned off.
The specific colorants used will result in a variety of crystal & backgroun=
d
colors. For example, nickel oxide generally produces and amber background
with electric blue crystals.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
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