shellac under varnish

[bases-loaded@juno.com]

Hi David -

Shellac is actually an excellent choice for a sealer coat under
"traditional" varnishes, but under the more modern Polyurethane
varnishes, which seem to comprise the majority of the product lines these
days, only dewaxed shellac will allow for proper adhesion between the
shellac and poly.  Polyurethane is very persnickety about what it adheres
to, to the point where it really doesn't even adhere to itself that well
unless proper techniques are employed.  And certainly, the natural wax
content found in conventional shellac products would prevent the poly
from achieving good adhesion.  That's my take on it, anyway....  With
dewaxed shellac, you are safe with any finish I can think of.

Mark Potter
bases-loaded@juno.com

On Thu, 28 Aug 2003 08:36:38 -0700 "David Love"
<davidlovepianos@earthlink.net> writes:
> Why is it that many varnish manufacturers advise not to use their 
> products
> over shellac.  It is my understanding that shellac was traditionally 
> used
> as primer coat for varnishes?
> 
> 
> David Love
> davidlovepianos@earthlink.net
> 
> 
> 
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