shellac under varnish

[Erwinspiano@aol.com]

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In a message dated 8/28/2003 2:00:10 PM Pacific Daylight Time, 
bases-loaded@juno.com writes:

> Subj: Re: shellac under varnish 
>  Date: 8/28/2003 2:00:10 PM Pacific Daylight Time
>  From: <A HREF="mailto:bases-loaded@juno.com">bases-loaded@juno.com</A>
>  Reply-to: <A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A>
>  To: <A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A>
>  Sent from the Internet 
>   David
>    I have typically used shellac for a sealer coat on new boards on the top 
> and bottom before the ribs and bridges get glued on. I like the sealing 
> properties and it keeps  dirt, glue & water from glue cleanup from impregnating 
> the panel during ribbing. I always sand and then coat with nitro cell. 
> products. No problems here as to adhesions. I use one good wet coat of the bullseye 
> in a can, ooooohh I can hear the cringing from hear. I spray it on. I quit 
> using varnish over shellac after I lost several finish jobs to the crinkles& 
> varnish is tooo slow to cure for my schedule. What can I say I'm varnish 
> impaired. Love the smell though.

              Dale

> 
> 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
> 


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