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Shellac - Caustic soda

G’day The action of caustic soda on shellac is simply to soften it so
that it may be easily scraped away. When applied to paint, it
reacts with the fatty part of the paint, allowing the remainder to be
scraped off. Caustic soda is not normally included in the term
’solvent’. When it makes things “disappear” like meat, for instance,
it reacts with the fat and forms a soap and glycerin. Contrary to
popular belief it does not ‘eat’ bone. It simply removes all the
fat, leaving the mineral part of the bone, which is how laboratories
prepare skeletons for display and study, and how bone carvers prepare
their work specimens. The reaction between organic materials and
caustic soda can be quite violent and it destroys part of the
structure. One of your correspondents suggested that caustic soda was
thrown into pits containing bodies. I suggest that this was not
caustic soda but quicklime (calcium oxide) which removes water from
the body, then the alkaline material slowly disintegrates. Chloride
of Lime (calcium hypochlorite) was used for the same purpose, and in
this case it acted as a bacterial deterrent, so smells and bacterial
reactions could not occur.

To prepare shellac for use, it is common to simply pour a little
ethanol or methylated spirit into a jar containing some of the flake,
covering, and just leaving it overnight. Further meth spirit can be
added later if needed.

Cheers for now,
John Burgess; @John_Burgess2 of Mapua, Nelson NZ