Poly on Wood (En Garde!)

[Duane Collie <drcollie@xxxxxxxxxxxxxxx>]

>From: Michael_Bird@domain.elided
>Subject: Please! Oiling the paint?

>>Duane wrote:   The polish puts oils back into the paint, and the
>>wax seals it all up.  Done like this, your finish will go a long time
>>looking like brand new.

>PLEEEEEEEEEASE!   Come on guys, don't buy that marketing crap...<snip>
>Like putting polyurethane on wood furniture.  Oil will not
>penetrate the clear coat.

Ruh-Roh Michael,

While Bimmers are my hobby, woodworking and furniture is my business! If
you think Polyurethane is a 100% complete sealer on wood then you've
probably not done much finishing yourself. In my business, my workshop
makes reproduction furniture and we use poly topcoats (2 coats) over our
aniline/shellac base coats. This is done to provide heat and water
resistance (note its not "proof") to the underlying finish. I developed
this finish over a 2 year period in the late 80's and experiemented with
every oil and/or water based poly and lacquer on the market. 

Our kiln-dried wide board furniture will still move seasonally up to 1/4"
on a 10" board due to moisture absorbtion in the summer and loss of same in
the winter (if in a heated environment). This is known as 'shrink' and we
allow for this movement with specialized furniture joints.  The poly does
not keep the moisture either in or out, even if all sides are sealed. 

Also, I encourage our customers to care for their fine furniture with
either a polish (preferably a beeswax/lemon oil) or a mineral spirits based
wax, both of which penetrate the poly topcoat.  

I also tell our customers to NOT use silicone based sprays (like Pledge) as
they will not only go though the finish but penetrate into the wood.  This
gives the refinishers fits at some later date as even if your completely
plane off the finish, the silicone remains in the wood (invisible to the
eye), but causes the subsequent new finish to 'fisheye' when its completed.

While you can probably put 20 or 30 coats of poly on a piece of wood and
probably seal it up pretty good (I think it becomes a clear resin finish at
that stage), the average piece of furniture with either a poly or a lacquer
finish is NOT a fully sealed finish.  To test yourself, simply get a piping
hot pizza in a box and throw it on the poly-topped table. Wait 10 minutes
and remove. See the white haze underneath that won't come out?  Heat and
vapor damage penetrating the poly topcoat.  The heat actually opens the
pores of the finish and when it cools will allow the finish to close up
with the moisture trapped inside.

BTW, for all you E34/E32/E39 owners (required BMW content) who have
scratched up wood on your console you can easily repair this yourself - go
to the body shop supply store in your area and get some microfine sandpaper
(600 grit) sand off the scratches, polish with the 1000 grit (sanding with
the grain - always), and then wax with a good carnuba paste wax. Will shine
like a new penny and easy to renew later on.
 
So endeth the poly/wood lesson for the day.

Duane Collie
SVR/ UUC / Bubba

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