-Test Castings with Ediphone wax-
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6/17/09:
The very first cylinder casting made, was done while the mold was
still at the machine shop. I had gotten so curious about how it was
all going to work that it dawned on me that I could do a very simple
and crude experiment before the mold was finished. A small mold
was made using aluminum foil. The foil was doubled over and then
wrapped around the end of the Edison phonograph mandrel. That became
the core, then the outer cylinder was made by forming another piece of foil
around a late Blue Amberol record box and removing it. The two mold parts
were joined at the bottom by folding them around together, trying as best
that I could to keep them concentric. This mold was only about 2.5 inches
tall, so if it worked at all, it was going to make a very short cylinder,
just enough to make some test recordings on. I got that all set and then
added one more piece of foil folded and rolled around the outside in
one piece to keep it from leaking.
About all I had around handy to pour in, as far as wax, was Ediphone
shavings and some cut-off ends of Ediphone blanks left over from
hacking them up into phonograph blanks. All into the old 6-cup
percolator coffee pot they went, and then it was put on to the kitchen
stove at a fairly low flame. At that time I had no thermometer, so I
was just guessing at when it was hot enough and runny enough to pour.
The black Ediphone wax soon melted, then I fished out the fabric netting
that was inside of those cutoff ends and then strained the liquid
wax as best I could through a tea strainer. After the straining it went
back on the stove for a few minutes to get good and hot before pouring.
Once poured into the mold the first thing I saw was how much and how
fast it shrinks as it cools. Being aluminum foil, the whole thing
cooled very quickly and the upper edge of the casting sank back down
about 3/8 of an inch, and the inside and outside edges were turned
up so that it formed a very concave meniscus on the top.
A half hour later it was cool enough to peel off the foil, and there
it was, a very rough casting. It was a bit of a struggle using sand
paper and a pocketknife to get it so that it would fit at all onto
the phonograph and shaver mandrels. Once that was done, then it got
shaved on the shaver down to its first good surface. It was smooth, shiny,
and black. I put it on the phonograph and made a few test recordings
and played them back. It was not very loud, and the recorder kept
wanting to glide up and out of the cut and just slide along the
top of the record without cutting it. But that crude little quick test
of a cuff cylinder did prove that it can work. Not very good at first
but it worked. So, as far as numbered castings, that was #0, the very
first attempt.
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A few weeks later on 7/16/09, after getting the mold back from
Keith in Clinton, the same kind of a test was repeated using the
same type of scrap Ediphone wax. I added a little paraffin to hopefully
soften it a bit for better cutting by the recorder, and I did heat the
mold in the oven at 400 F for a time before pouring. Before the mold
went into the oven, it was treated with graphite on all surfaces
exposed to the wax. That idea came straight from the old book.
A lot went wrong with that very first casting in the mold.
The wax leaked out the bottom of the mold where the core seals to
the base. That was later solved by making a gasket out of paper
to seal that joint where the core meets the base. It was funny because
that very first time as poured, the wax kept going down very fast and
at first I thought it was the shrinkage, but it kept on going and going
so I knew then that it was the bottom leaking. So, right then I imagined
the big plug of wax that was going to be inside of the bottom of the
hollow core. This mold, being somewhat more massive than the tiny
aluminum foil mold takes a lot longer to cool. It was about a 45 minute
wait until the core was twisted out.
Then, soon after the core came out, the outer steel cylinder was removed
with the wax casting firmly bound inside. Now the supreme test was on!
This might never release and if it doesn't, this whole works is a failure...
Well I waited and waited and held it up and tapped on it with a block
of wood, and that wax stayed in there. Just as it was looking hopeless
I held it up to the light lengthwise and caught a glimpse of daylight
along one outer edge of the wax, between the wax and the inside of
the mold cylinder. It was shrinking! A few more gentle taps by hand
and the darn thing slid out and almost got away from me and smashed on
the floor. But, I caught it and set it down. It worked! The first time!
Now as to whether or not this casting was going to be good for anything
remained to be seen. It was kind of a mess inside, one end was too big
for the mandrel, the other end needed to be reamed. The sloppy end
eventually got a piece of cardboard taped in with scotch tape and that
made this rough cylinder casting stable enough to be shaved.
It was a short cylinder, about 3 inches long due to the mishap with the
leaking wax and another mistake I made while shaving it. It got messed up
on both ends, from two different mistakes that I made. I recorded slightly
better than the previous attempt made in the foil mold. This casting
#M1, is a little noiser than #0 was, because of the added paraffin.
It cuts a little better, but it is noisier too. That is a pattern of
how this stuff works. Everything is a balance and it's all interdependent.
Fix one thing, and something else unintended happens.
So this first casting shows that cutting can be improved at the expense
of adding some noise.
But, the best thing about that first test of the mold is still that the
casting does release! That was the big critical moment and it worked!
The wax shrinks as it cools, and after a while the
cylinder just falls out. The trick is to remove the core before it binds
on to the core. If the casting binds on to the core, that will be a
completely failed casting because the only way to get it off without
a real hassle is to put the core with the casting on it, all into the
freezer and wait until the casting cracks off.
So, if the core is pulled too early, then the casting distorts out of
round because it's still to soft. Too late on removing the core
and it will not budge. There is about a 2 to 3 minute ideal time
to pull the core. The old book mentions that too. It says that
experience shows when the ideal time is to twist out the core.
This basic experiment using melted scrap Ediphone wax with various
amounts of paraffin added formed the pattern for the first 12 castings.
They varied quite a bit. #M2 was better because it came out the full
6 inch length of the mold because the bottom paper gasket was added
to prevent the leak. Without the gasket, there is indeed a 2 inch
long solid plug of wax that flows up inside of the hollow mold core.
There were some failed castings in the first dozen, several got
scrapped and remelted. Then along toward the end I had to throw in
some Dictaphone "Nuphonic" wax, which is slightly different than
Ediphone wax. Those two waxes, plus paraffin made the most horrible
noisy grating-sounding stuff you ever have heard in your life!
I was running out of wax... What next?
It was at that time that I no longer had any choice. If I wanted to
continue casting experiments I needed more wax, so it was time to
make some from scratch. It was now late in July of 2009, and I had
just made 12 castings and had shaved them and recorded on them.
Some were "ok" as tests, but certainly not anything worth any more
than a "learning experience".
Those did show that Ediphone wax tends to get harder after being
remelted and recast. They also show that this can be partially
corrected for by adding a bit of paraffin, but then paraffin also
adds noise. Many lessons were lurking in the data collected from
those early tests. Things like cooling too fast and unevenly using
a fan blowing on the mold were hinted at as big noise-causers.
Things such as casting into a cold mold were tried as well, with
resulting disasterous sounding particularly aweful cylinders.
Next Segment: Getting the materials.
