[CAUT] finish/moisture barrier

[Delwin D Fandrich]

Yes, epoxy does provide a true vapor barrier, but.it takes thicknesses that
rather preclude its use on piano soundboards. 

 

As well, most epoxies break down over time due to exposure to ultraviolet
light so they need their own finish protections. When I use very thin
("coating") epoxies on piano soundboards I sand most of the coating away
after it has cured leaving just the amount that has penetrated the surface
of the wood and then I coat that with a clear finish that contains UV
blockers. This is not intended to be-nor is it-a vapor barrier.

 

ddf

 

Delwin D Fandrich

Piano Design & Fabrication

620 South Tower Avenue

Centralia, Washington 98531 USA

del at fandrichpiano.com

ddfandrich at gmail.com
Phone  360.736.7563

 

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Bob
Hohf
Sent: Wednesday, February 16, 2011 6:18 AM
To: caut at ptg.org
Subject: Re: [CAUT] finish/moisture barrier

 

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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