bill edwards on sun 3 apr 05
Is there a dispute between minds here going on again?
Oh well, lurkers can now get in here while everyone
else is busy.
Thixotropics. Doing the hokey pokey with thickening
agents.
CMC - dry CMC needs to be added after it is mixed
really well using cold water. adding it dry to a glaze
before mixing it with water will clump up and will be
almost impossible to seperate. Use a small hand mixer
like those found in larger stores that are used for
mixing fruit drinks and ice crushing. Almost a
mini-homoginizer. CMC is carboxymethylkcellulose.
Don't let the long name scare you at all. I found a
web site you can visit and I used it more in my past
business than I do now. Good material but can develop
bacteria over time unless you use a bio-active
anti-bacterial. Best thing to do is just mix in small
amounts and use it up or store it in a tight container
like a mason jar once you hydrate it with water.
Here's a url for more information. And you are right,
CMC is often used in brushing glazes but is also
usefull for dipping in some circumstances because it
can impart additional hardness to the glaze shell. Try
about a 1/4 - 1/2 cup CMC to 1 quart of water and mix
until you get a clear yellow syrup 'thick' liquid. You
can make it as thick or thin as you like. This is what
you would add to your glaze for either dipping or
brushing.
http://www.ratson.com/chemicals/carboxy.htm
Epsom Salts - You can add dry or a strong solution
made by adding water to a specific amount of epsom
salts. There's several formulas for this quantitive in
the archives. My own idea on it would be mix 1 cup
epsom salt (magnesium Sulfate) to enough warm water to
dilute it completely (this may take several minutes)
and add small ammounts to your glaze if you go that
route. I have a formula that I use as part of the dry
mix phase. For your 1500 ML batches you could drop it
by dropper from the liquified pre-mixed version or add
what would amount to 0.5%-1% dry gram weight and add
more if needed. The suspension may appear thicker than
it actually is once it sets for awhile. Try
re-stirring and dipping. Rheology plays here and ionic
structure. Sorta like a magnetic field in liquid
motion that appears hardened up once the motion has
ceased. Some people use the eye-ball method of
dropping a drop of glaze back unto its self and once
it starts to puddle you have reached the point of
dipping. That can be a little tricky and needs
personal adjustment and testing by the potter. I used
to own a viscometer but you can get by without one.
Personally I usually wait it out for a few hours if
not a day prior to using the glaze, you will figure
out the correct viscosity for each glaze over time but
the aforementioned version should suffice till you do.
I don't think theres a need to go back into covalent
and ionic structure since that has been gone over and
over, and over many people's head who's looking for
simple answers. If you look for the hard science most
of it is in the archives. Epsom Salts is also very
good for tomatoes and roses just in case anyone is
interested? Here's another url for those interested.
http://www.epsomsaltcouncil.org/
Neither are toxic and are used in various ways in the
health industry.
Clayart is loaded with the greatest minds in pottery
anywhere in the World. Of course our group is intense,
great thinkers and worriers all have the same things
in common and the finish lines and trophies usually
are well worth the game once the score is tallied up.
Sore loosers get Mel's red button and a hard kick at
times! Rid-A-Fuss the next invention for the internet.
Bill Edwards
Edmar Studio and Gallery
As a relative beginner in pottery I'm confused by the
use of the above
ingredients --when to use them. Can CMC be added to a
glaze that is
already mixed or must it go in at the dry stage?
Bentonite is often used
in the dry state at 1 to 2% it seems --I know that it
helps to keep the
glaze ingredients in suspension but can CMC be used in
the same way.
I'm told that CMC is a brushing medium ?
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