Subject: Re: baidarka What is varnish?
From: Mark Reuten (clinker@look.ca)
Date: Fri Feb 16 2001 - 09:08:18 EST
For all those tuning into this new discussion, the best source of info on
finishes is a book called "Understanding Wood Finishes" by Bob Flexner. He
dispels myths and gives good solid application advice based on scientific
research. Unfortunately he does not deal with the subject of marine
applications but the basics are all there. Don't pass this book over if you
do allot of finishing.
Mark Reuten
www.nomadboatbuilding.com
----- Original Message -----
From: "Samson Family" <bill.samson@tesco.net>
To: <baidarka@ns1.intelenet.net>
Sent: Thursday, February 15, 2001 9:18 AM
Subject: baidarka What is varnish?
> Paul asks:
>
> >So what exactly is varnish?
>
> I'm no expert, but I have some experience with using different kinds of
> varnish.
>
> Traditionally, varnish would be made from some gum dissolved in
turpentine,
> often with linseed oil added. The simplest stuff was based on pine resin.
> The poshest stuff used copal, or in some cases amber. It cured by a
> combination of evaporation and (I believe) oxidation - which could take
some
> days, or even longer.
>
> These days, most varnishes seem to use a synthetic gum, but other than
that,
> the oil-based ones seem to cure in the same way. They do have different
> properties from the natural gum ones, I've found. For instance, natural
gum
> varnish (once cured) can be rubbed down then polished to a gloss using
> Tripoli powder - synthetic gum varnishes, in my experience, can't be
> polished by this method but remain dull after rubbing down.
>
> Modern two-part polyurethane varnishes use a chemical reaction between the
> two components to effect a cure (rather like an epoxy resin). These give
a
> tremendously hard-wearing finish.
>
> Then again there are the new water-based acrylic varnishes, which are
> pleasant to use (- I did my kayak frame with this stuff).
>
> Aeroplane dope can be considered a type of varnish, as can egg-white!
>
> I suspect that when people suggest mixing in 'varnish', they're talking
> about the old-fashioned sort, based on a natural gum, turpentine and
> possibly linseed oil. This is hard to get nowadays, though you can always
> make your own! Numerous varnish recipes can be found in books on violin
> making.
>
> Unfortunately, this field is full of confusing and ambiguous terminology -
> words like "lacquer" can mean just about anything, and few authors say
> exactly what they mean. It's a bit like going to your local DIY store and
> asking about the species of the timber on sale there. Even the best
> informed of these places will be stuck after telling you it's hardwood, or
> softwood, or maybe "whitewood" or "redwood" (- whatever the Hell they
are).
>
> <Sigh!>
>
> Bill Samson
>
> PS - A question to those of you who know about these things. Old Aleut
> paddles are often painted back and red. Was conventional oil-based paint
> used, or was it a suspension of ochre, soot or whatever in water? I've
just
> about finished carving a new one, and I'd like to finish it in the proper
> way.
>
> -
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