Bruce Girrell on mon 30 may 05
The unity formula that I provided in my first post on this subject was
incorrect.
Here is the post again with the corrected values. Sorry about that.
Does anyone out there happen to know if there is a flux that is
particularly
effective in melting rutile/ilmenite?
I just fired a glaze test series that included varying amounts of rutile
and
ilmenite. The results all show that I am simply not melting the rutile and
ilmenite particles. Examination under a microscope shows that the edges of
the rutile particles are not even being attacked. They look almost identical
to particles prior to firing.
The recipe that I am using is
Custer 41
Silica 33
Dolomite 12
Whiting 7
OM4 7
Rutile 4.5
which yields a unity formula of
CaO 0.51 Al2O3 0.33 SiO2 4.02
MgO 0.23 TiO2 0.20
K2O 0.17
Na2O 0.08
Fe2O3 0.01
Si:Al = 12.20
The formula falls nicely within the cone 10 limit provided by Rhodes except
for the fact that Rhodes includes 0.1-0.3 Boron.
The formula is similar to what John Britt provides for a rutile blue
formula
except that Silica is too high. The glaze does fire to a satin appearance,
not glossy, so maybe decreasing the silica might help, but would that
improve the melt on the rutile?
I would appreciate any suggestions regarding how to improve the melt for
rutile.
Thanks,
Bruce "feeling even more humbled" Girrell
Paul Herman on mon 30 may 05
Hi Bruce,
I think Rhodes may be pointing in the right direction.
TiO2 is refractory, (melting point 3362F, Seger cone 38) which is why it
works so well as an opacifier at cone 10. Those little chunks just float
around, and don't melt.
I made up a stain to use over raw glaze, containing half Red Iron, and
half rutile. It gave great gold colors and crystalised in the cooling.
Real sparkly. If you got it on too thick, it would get rough, blister
and generally do ugly things. By adding in 10% boron frit (3134) the
problems went away, and it always melts smoothly now. You just have to
blugeon that Titanium into melting, and boron makes a good club for that
stuff.
I would consider small additions of boron to your desired glaze.
My teacher Dennis Parks was impressed with the rutile/iron pigment, so
he named it "Herman's Perfect Rutile Stain". Formula:
Red Iron ox 45
Rutile 45
Frit 3134 10
Good glazes,
Paul Herman
Great Basin Pottery
Doyle, California US
http://www.greatbasinpottery.com/
----------
>From: Bruce Girrell
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Melting rutile - correction to previous post
>Date: Mon, May 30, 2005, 9:26 AM
>
> Does anyone out there happen to know if there is a flux that is
> particularly
> effective in melting rutile/ilmenite?
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