Steve,7000 series is what I have seen. I think that flat enders were made until
about 1903,and yes, the surface is very thin, with thick ribs, the ribs on the
cylinders. Are made. With a special knife, and this was done when the record
was still expanded in the mold, and the record hot, however cool enough to
retain the shape. And when they had sat a few days the ribs were Reamed to fit
the taper of a phonograph mandrel. The comp was changed about 1904 for the
round end records. Ebonite (which was melted at 350 degrees). And wet copper
powder added to this, then stearic, soda aluminate, ceresin and pine pitch.
What ebonite actually is, is a mystery, I do not think it is hard rubber, as
ebonite is called for other purposes, but may have been a trade name of montan
wax . The formula says you can sub caranauba with "Ebonite", and montan has
properties similar to carnauba, and you do not smell rubber when you melt a
1905 era GM record, you can shure smell the pine tar.
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