will edwards on wed 27 dec 00
Hello,
In doing some analysis and looking for my own personal replacement for GB=
which I have actually corrected for my glazes, I noticed something in com=
mon
that I am sure some of you are aware of.
I also have experimented with artificial thickening agents but went back =
to
working with what most of us have on board as potters.
Gerstley Borate (Soon to be all gone)
Epsom Salts
Talc
bentonite
Dolomite
These items listed above have been known to work well for improving hardn=
ess
and fixing a slurry in the bucket for a long time and under various
conditions. Those same items have one common ground. (Magnesium) Magnesiu=
m
carbonate is kin to calcite which will bubble like mad when subjected to =
an
acid but magnesium will only slightly bubble. Magnesium ions are not the =
same
size as calcium ions and in calcium a glaze containing magnesium lays bet=
ween
the layers of calcium where present. =
Mylanta (tm) uses Calcium Carbonate and Magnesium carbonate so the safety=
issues would be minimum unless you take into account LOI or loss of ignit=
ion
and breath Magnesium fumes which are toxic. (Manganese fumes are as well)=
It
also answers why it is a good suspension producing agent for thier produc=
t.
(Calcium/Magnesium) =3D colloidal aggegration or hand-holding with partic=
les of
ionic charge. Its the attraction I suppose like metal to a magnet? Anonic=
,
cationic, non-ionic and ionic. On and on!
So we have flux active materials here as well as Colloidals. Insert phone=
tics
here - (Macaloid) Vee gum T and other Cellulosics offer a similar fix bu=
t can
alter the appearance due to dilution of the oxide content under a gelled
formation. Getting the parameters set for the use of these materials in a=
fritted glaze is of great importance in regards to color and absorption r=
ate
of the biqued ware. Remember polymer colloids is what I am used to workin=
g
with so I am just beginning to hit on the glaze suspension theories.
In ending - should anyone be testing the use of substituting these easy t=
o
find minerals over gums that would be willing to share information please=
contact me off-list if you choose to. All information I can garner will b=
e
placed back to our listgroup in the best format a country alchemist in th=
e
South can do. I bet many of you are now wondering about glazes that don't=
need
magnesium in them? We can fix those as well over some coffee. I don't pre=
tend
to know the answers so I call on the rest of you to surface with some bet=
ter
ones.
William Edwards
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