need advise: high alkali crucible melt

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I am planning to make sodium/potassium silicate through the furnace
route in a crucible furnace.  I am unfamilar with precautions
necessary for very high flux mixtures as opposed to regular soda
glass.

Will alkali "fumes" hurt my kiln.  Will molten alkali destroy a
regular glass crucible?  I have easy access to a small electric
ceramics kiln (in my backyard), and also to a large gas crucible
furnace built for metal casting (acquaintance's back yard).

For my first attempt I plan to use sodium hydroxide and glass powder
and fuse them at only 600-700C for 3-6 hours.  The mix will be about
equal weights sodium hydroxide and glass powder.  I would then pour
that molten mixture into Ice water and crush the powder in order to
dissolve it.


Does anyone have any experience or learning regarding this?

Re: need advise: high alkali crucible melt

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You've probably already solved the problem: if so, I would like to know
what happened - you can reach me at zorondoug at yahoo if you feel like
sharing.

I would also like to know the purpose of this experiment, as I may be
able to discern another method for accomplishing the task: a standard
ceramic crucible will certainly be damaged by high concentrations of
molten alkali, but it might hold up long enough to do whatever you need
to do - assuming you can accept the amount of crucible that will become
dissolved in the finished product. I would think that a graphite
crucible would be the least suceptable to erosion, but quartz would be
my second guess: those researchers in my experience who have put nasty
things into their crucibles have opted for quartz as a disposable
substrate (it might take awhile to eat through the quartz, probably
longer than to eat through ceramic, but they amortize the cost of the
crucible against the value of whatever it is they are trying to do).
The quartz would not contaminate the finished product with calcium, but
you would probably require some trial-and-error to determine how much
of the quartz silica is being added to the silica of the glass in your
batch. With either type of crucible, it will be expensive.

Another avenue in this line of research would be to contact crucible
manufacturers, directly - they have undoubtedly run across this problem
repeatedly and they are sometimes willing to share their wisdom (some
of those experts are really nice people who identify with the home or
small-business researcher, and others are just pills - goat pills).
Just be willing to spend more than three phone calls on it.

As for your concerns about alkali - they are all justified. Don't let
it get on your skin, or you will feel a soapy sensation when you wash
it off: that sensation is your skin, dissolving in lye (at least, that
is, according to my chemistry teacher in college). Do NOT breath any of
the vapors - rigging a powered external air supply would be best (I
don't know whether the exaust of a vacuum cleaner fed into a
vacuum-cleaner extension hose leading to somewhere near the face would
work well or not - it would be clumsy, no doubt). Keep some vinegar
around for rinsing things such as your hands, and make certain to
either wear booties or wash the soles of your work shoes before wearing
them into living areas, especially if you have pets or children. Check
with your local safety-supply outlet (they are common everywhere - or
should I use my word-a-day, "ubiquitous": sounds nasty) - they will
have specialized breathing equipment for almost anything you might come
up with as well as protective gloves, etc.

I sure am curious about what you are doing: I've got a background in
chemistry, medicine, electronics, photography and music, among other
things, and I can't think of any use for what you are making, unless it
is just a precursor for something else. Please do let me know what
you're doing - I'm willing to sign a non-disclosure agreement.
(Curiosity costs me more than any other pastime, I believe).

Keep it turning …

--
R. Douglas Wiggins Jr.
"Zoron" - The Original (circa 1954)

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