What a fascinating subject this is and Julian Dyer is so correct in
saying how complex it is. For my penny's worth I have a wonderful book
entitled " The Handyman's Enquire Within" - making, mending renovating
edited by Paul N Hasluck and Published by Cassell in 1910. This is
basically an early book on "do it yourself " - 570 pages of pure
fascination covering every subject in alphabetical order.

Under the subject "Varnish" there are subheadings such as Brown Spirit
Varnish, Furniture varnish, Shellac varnish, white hard spirit varnish.

Shellac has subheadings such as Bleached or white shellac, Button
shellac, Garnet shellac, orange shellac and shellac water varnish. All
mainly produced from  a gum product of insect life in India and Asia,
hence the use of the word "lac" in India for 100,000 rupees or anything
else, since enormous numbers of these insects were involved.

For lacquer there is only Chinese or Japanese lacquer work and this
would certainly not have been applied to Pianos !  it entailed a
minimum of 33 coats  to produce perfect work.  It  has no connection
with Shellac but the lac is taken from an incision in the trunk of
the Rhus Vermicifera tree.

French polishing is also covered in great detail.

If any of this information might be of interest to anyone I would be
pleased to send further info or scan the pages of interest.

Alan Whytock