James Freeman on mon 8 feb 10
Gay...
The stuff in your jar may very well no longer be sodium silicate. It is my
understanding that over time sodium silicate reacts with carbon dioxide fro=
m
the air to become silicic acid (which can polymerize and form clumps) and
soda ash. While I am sure the reaction is reversible in some way that is
beyond my understanding of chemistry, why bother? Since sodium silicate is
dirt cheap, I'd just replace it.
Just my thoughts.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I should
not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/clayart/
On Mon, Feb 8, 2010 at 5:26 PM, Gay Judson wrote:
> Recently I got out my jar of sodium silicate to make some terra
> sigllata. I poured out the amount I needed and put it away. Later I
> wanted a bit more and used a spoon to take out what I needed only to
> find that just below the surface it had crystalized. I also found
> later that it had formed clumps of crystals in my terra sig.
> Question: can I salvage the rest I have in the jar? Or do I just
> toss it out and by new? I don't use it very often so I hate to have a
> new jar sitting around turning to crystals unless I can reconstitute it.
> Thanks, Gay Judson in San Antonio
>
Gay Judson on mon 8 feb 10
Recently I got out my jar of sodium silicate to make some terra
sigllata. I poured out the amount I needed and put it away. Later I
wanted a bit more and used a spoon to take out what I needed only to
find that just below the surface it had crystalized. I also found
later that it had formed clumps of crystals in my terra sig.
Question: can I salvage the rest I have in the jar? Or do I just
toss it out and by new? I don't use it very often so I hate to have a
new jar sitting around turning to crystals unless I can reconstitute it.
Thanks, Gay Judson in San Antonio
James Freeman on tue 9 feb 10
On Tue, Feb 9, 2010 at 4:48 PM, Neon-Cat wrote:
>
> To get a reaction between liquid
> sodium silicate and carbon dioxide you have to work at it by pumping
> pure carbon dioxide through the solution.
Marian...
Hamer and Hamer disagree with the sites you Googled for your information, o=
r
at least with your interpretation of those sites. Page 344, Sodium
Silicate:
"Sodium Silicate is difficult to store. It combines with carbon dioxide in
the air to give sodium carbonate and silicic acid. It's deflocculating
power is then altered."
I knew I had read such, but could not remember where. I have no idea if
they are right, or if your Google information is, but since the stuff is a
whole $5 for an entire quart, why take a chance?
Be well.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I should
not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/clayart/
Neon-Cat on tue 9 feb 10
Gay, no matter how it=3D92s made or the weight ratio of SiO2/Na2O, sodium
silicate liquid may contain or form a small amount of suspended
particles that can accumulate over time at the bottom of a container.
This usually occurs as a thin skin of dehydrated sodium silicate forms
on the surface of the liquid then sinks to the bottom. You probably
caught the suspended particles on their way down to the bottom. Over
time, sodium silicate may also form small crystals with metal salts if
the container has been contaminated (remember crystal gardens?) or if
your mixing water is very hard (contains high levels of calcium and/or
magnesium, as in many parts of Texas). You can use the sodium silicate
as is and just avoid the particles or you can strain or sieve it. It
will not have changed from being sodium silicate although its
SiO2/Na2O ration may vary slightly from the original. I=3D92d fine-sieve
the terra sig before using it -- you must have some soluble metal
salts in suspension to give a slight reaction. Store the sodium
silicate at room temperature for best results, avoiding freezing
(irreversibly changes in properties may result) and temperatures over
140 F (can go up to about 200 F). Stirring or shaking periodically
will prevent silicate dehydration if you really just have to have
particle-free sodium silicate. A plastic spoon might work best (as
opposed to stainless stain) for spooning-out small amounts.
James, the atmosphere contains (in mole percent) 78.084 nitrogen,
20.9476 oxygen, and 0.0314 carbon dioxide. There=3D92s more argon in the
air we breathe than carbon dioxide. To get a reaction between liquid
sodium silicate and carbon dioxide you have to work at it by pumping
pure carbon dioxide through the solution. Liquid sodium silicates are
very non-reactive for all intents and purposes as used by potters and
they store well. Although sodium silicate liquids have long shelf
lives many manufacturers recommend that they be used within a year
after the date of manufacture if you are really, really fussy. I=3D92m not
worrying about mine or worrying about always ordering fresh batches.
If you=3D92re into making sodium silicate films or sealants for your
ceramics (through heat treatment), a sodium silicate film may develop
a white appearance (efflorescence or blooming). In this case, over
time, carbon dioxide in the atmosphere can react with the sodium in
the sodium silicate coating to form sodium carbonate on the surface of
the film. This occurs most often in hot, humid conditions.
Silica gels may be formed by adding acid to solutions containing
sodium silicate, so acids are to be avoided in sodium silicate
containing liquids.
PQ Liquid Sodium and Potassium Silicates -
Storage and Handling
http://www.pqcorp.com/Literature/bulletin_17-70.pdf
Dispersion Characteristics of Soluble Silicates
http://www.pqcorp.com/Literature/bulletin_17-67.pdf
PQ Corp. Frequently Asked Questions
http://www.pqcorp.com/TECHNICALSERVICE/Frequentlyaskedquestions.ASP
Marian
neon-cat.com
Neon-Cat on wed 10 feb 10
This may horrify you James, but there is a lot in Hamer and Hamer that
makes me cringe. It is a good jumping off point as a basic reference.
It is a dictionary and there is so much too keep current on; it is
quite good as far as it goes.
I've done and thought and worked in chemistry a long time, James, and
it is not just a matter of Googling something or reading Wiki articles
or grabbing a quote from some potter book. Sodium silicate chemistry
is well-covered even in basic first year general chemistry college
classes and texts. There is no chance to take keeping sodium silicate
around, so I'll not be worrying and $5.00 is sometimes the world to
me. Why waste a few bucks needlessly? It is not hard to deflocculate
kaolin-type clays anyway.
This is a chat list and I'll do some sharing from time to time because
clay and clay science is all I think about and chemistry is my area of
expertise. Ivor recently wrote me an angry email about "staying out of
the kitchen" on Clayart because I was "preempting" him, or something.
Then there is you. Believe what you want to believe. It doesn't alter
a thing for me. And it is certainly not worth getting into some
tediously wordy argument with you or others on-list to prove some
point when there are things to make and life to live.
Marian
Neon-Cat
On Tue, Feb 9, 2010 at 9:11 PM, James Freeman
wrote:
> On Tue, Feb 9, 2010 at 4:48 PM, Neon-Cat wrote=
=3D
:
>
>>
>> To get a reaction between liquid
>> sodium silicate and carbon dioxide you have to work at it by pumping
>> pure carbon dioxide through the solution.
>
> Marian...
>
> Hamer and Hamer disagree with the sites you Googled for your information,=
=3D
or
> at least with your interpretation of those sites. =3DA0Page 344, Sodium
> Silicate:
>
> "Sodium Silicate is difficult to store. =3DA0It combines with carbon diox=
id=3D
e in
> the air to give sodium carbonate and silicic acid. =3DA0It's deflocculati=
ng
> power is then altered."
>
> I knew I had read such, but could not remember where. =3DA0I have no idea=
i=3D
f
> they are right, or if your Google information is, but since the stuff is =
=3D
a
> whole $5 for an entire quart, why take a chance?
>
> Be well.
>
> ...James
>
> James Freeman
>
> "All I say is by way of discourse, and nothing by way of advice. =3DA0I s=
ho=3D
uld
> not speak so boldly if it were my due to be believed."
> -Michel de Montaigne
>
> http://www.jamesfreemanstudio.com
> http://www.flickr.com/photos/jamesfreemanstudio/
> http://www.jamesfreemanstudio.com/clayart/
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