Brown wax making and casting

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Chuck
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Brown wax making and casting

Post by Chuck »

http://youtu.be/LrR9h9fu324

The above is a link to a youtube video that
shows a few scenes of brown wax being made
and then being molded into a blank cylinder.

The wax batch #84 was made Friday, 8/16/13.
The first blank cylinder M255 shown being cast
from batch #84 was made Saturday, 8/17/13.

The reaming and shaving and test recordings
were done on M255 the following Monday, 8/19/13.

This video runs for only 5 minutes and shows
only a few of the highlights.

The clear liquid is hydrated aluminum, which
is made with distilled water, sodium hydroxide (lye), and a small amount of pure
aluminum metal. This solution is filtered
until water-clear, then added to the
melted stearic acid in small amounts throughout the cooking. There are (16) such
"portionwise" additions. The whole wax batch
takes about 2.5 hours to complete.

At the beginning, the temperature is 190 C.
After the first (6) additions of hydrated
aluminum, the temperature slowly rises for
following additions, as the reaction itself
becomes exothermic, throwing off its own heat,
and adding to what the stove fire puts in.

Finally, toward the end of the reaction, the
temperature rises to 270 C, which is 518 degrees F.

In this final stage during the
high-temperature end of the process, the
increased solubility of the saponified stearic
is taken advantage of at this high temperature
in order to assure complete combining of
the crusty precipitate that you can see in
the video.

This temperature is well over the flashpoint,
and if made in a shallow container, it will
catch on fire. The tall pot prevents this.

Then, once everything is thoroughly combined,
the last 25% of fresh stearic is added,
cooked in a bit at 250 C, then the temperature
is lowered to 232 C (which is 450 F), for
the remainder of the cooking, which then later
also involves the addition of a small percentage of ceresin wax that tempers the mix
and also makes the final brown wax non-hygroscopic. (it does not absorb water).

The casting process takes just under 3 hours
from the time the mold goes into the preheating oven, until the casting comes out.

I hope that this rather lengthy explanation
adds a bit to the short vid.

Chuck
"Sustained success depends on searching
for, and gaining, fundamental understanding"

-Bell System Credo

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