[CAUT] finish/moisture barrier

[Brent Fischer]

Hi Bob,
    The Forest Products Lab in Madison, Wisconsin also deviseda test to determine the effectiveness of commercial wood finishes.The results after three coats of finish and 14 days of drying time.Lacquer gave only 19% water vapor protection.  Shellac came inat 39%.  Varnish varies with spar varnish only at 30%, urethanegoing up to 37% and polyurethane varnish was the best finishtested to exclude water vapor at 66%.
Brent
--- On Wed, 2/16/11, Bob Hohf <rhohf at centurytel.net> wrote:

From: Bob Hohf <rhohf at centurytel.net>
Subject: Re: [CAUT] finish/moisture barrier
To: caut at ptg.org
Date: Wednesday, February 16, 2011, 7:18 AM




 
 






 



According to research done at the Forest Products Laboratory in
Madison, WI, the only wood finish that provides a true moisture barrier is
epoxy.  My source on this is a class at a Wisconsin Days Seminar in the
80s taught by a Forest Products researcher.  For information on the
relative moisture resistance of various finishes, see Table 16-2 of Wood
Handbook: Wood as an Engineering Material, published by the Forest Products
Lab. 

   

Bob Hohf 

   



From:
caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Brent
Fischer

Sent: Tuesday, February 15, 2011 10:44 PM

To: caut at ptg.org

Subject: Re: [CAUT] Steinway rebuilds 



   


 
  
  Ron, 
  
     
  
  
     The research I mentioned was pertaining to
  permeability issues , sorry 
  
  
  that wasn't clearly stated. The reports that you claim
  about increases in 
  
  
  stability are probably design related not finish
  differences, and are 
  
  
  just as speculative as me saying lacquered boards need
  double 
  
  
  duty damp-chasers. If I indeed implied that varnish is a
  determining stability 
  
  
  factor, well, I'll back the truck up on that one.
   The real question I have  
  
  
  is if you know that varnish provides a better
  moisture barrier in the first  
  
  
  place, why use a coating with less moisture sealing
  properties?  
  
  
  Because it's easier? 
  
  
     
  
  
    
  
  
  

  --- On Tue, 2/15/11, Ron Nossaman <rnossaman at cox.net>
  wrote: 
  

  From: Ron Nossaman <rnossaman at cox.net>

  Subject: Re: [CAUT] Steinway rebuilds

  To: caut at ptg.org

  Date: Tuesday, February 15, 2011, 8:43 PM 
  
  On 2/15/2011 9:18 PM, Brent Fischer wrote:

  > 

  > I'm going to take the high road on responding. Research proves my

  > point, I'm just repeating it.

  

  Research? On piano tuning stability as a result of using varnish instead of
  lacquer on soundboards? That would make entertaining reading.

  

  

  > Proving stability differences is just a mute point.

  

  Well, no. That seems to be exactly the point.

  

  

  > However, too many rebuilders use lacquer on

  > boards because it's easy, not because it's in the best interest of

  > the instrument.

  

  At least a couple of techs providing service to my lacquered soundboard
  redesigns have reported that they are notably more stable than the original.
  There are a number of parameters for tuning stability in design and build of
  soundboards that are argued by non designers and builders of soundboards, but
  there is ample evidence that varnish is not the magic ingredient that
  provides stability.

  Ron N 
  
  
  
 


   



 





      
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