On Jun 19, 5:03*pm, SparkyGuy wrote:

snip

organic varnish or polyurethane.

These are somewhat different materials. Presumably the term 'organic
varnish' simply means any old fashioned oil based coating, from
linseed oil, tung oil and the like. The PU can be oil based or water
based, the latter not as effective as a moisture barrier, which is
likely the intent of the request. The dual coating may reduce warping
of the boards, but is not usually done on quality moldings.

Joe