Jim writes:
> I just watched the video of the steam paint removal on the door jamb of the
> barn. The paint is completely removed& then John says that the next step is
> to prime& paint.
> What about a 1st layer of boiled linseed oil/turpentine? I've been advised
> by Duffy& the guys at Fine Paints of Europe and others that on old dried up
> wood like this there needs to be that 1st layer otherwise the oil in the
> prime is just sucked out and there is no adhesion.
Don't pay any attention to that man behind the curtain. As you can see,
my videos are true-grit worksite productions. They are not scripted
high-value hollywood productions like the movies or This Old House TV
show we are all used to watching on the screen. I just shoot, work, and
comment on what ever comes to mind. Since this video is mostly about
paint removal I don't get into everything else about painting. For
example, the next video in the series shows Wet Abrasive Scrub, which is
actually the next next step. Later videos in the series do show
pre-treatments (include the setup for testing four different
pre-treatment materials), priming, top coats, etc.
Actually we usually do a pre-treatment like you describe, with the type
depending on the surface conditions and situation. Here's an excerpt
from my book on windows, most of which applies to exterior wood siding
as well:
9a. Pre-Treat. Apply a penetrating pre-treatment to the bare wood. There
are two types, 1. Paintable water-repellent preservative, 2.
consolidating oil-resin. Paintable water-repellent is suitable for sound
wood surfaces. (if waxy paraffin type (Forest Products Lab's WRP Recipe,
Thompson's WaterSeal, or similar) apply to all surfaces of the sash, if
sticky oil or resin type do not apply to sash edges (the surfaces that
run in the jamb's sash tracks) and face margins (the narrow strip where
the face of the sash rubs on the parting bead or the stops)
Consolidating oil-resin treatment is suitable for gray weathered wood
surfaces or surfaces that are somewhat "soft" or more porous than
perfectly sound wood. The traditional recipe for this treatment is
linseed oil and turpentine. I no longer use linseed oil because it is
susceptible to mold and fungus attack. (acts like frosting on the cake
for the critters that eat the wood) I now use a 50%-50% mix of mineral
spirits and oil-based alkyd resin varnish or a proprietary product
(Flood's Penetrol, or similar) Just to confuse us all, there are some
combination products that are suitable. (California's Storm Stain
Penetrating Wood Stabilizer, or similar) Water-based products of both
types MAY be suitable, but all my experience and this recommendation is
for oil-based products.
A pre-treatment may not be necessary if all the wood is perfectly sound
(as with all new wood) and a very effective primer is used, but I find I
can lengthen the service life of the paint coatings on old wood with
this "fine tuning" of the coating system. Scientific studies at the
Forest Products Laboratory have demonstrated that a paintable water
repellent preservative effectively adds to the protection of the wood
and dramatically limits fungal decay extending the wood's life.
Penetrol is an oil-based product made of mineral spirits, linseed oil
and alkyd resin that penetrates deeply into the wood surface. The
mineral spirits evaporate leaving behind the oil and resin that cures
and consolidates loose fibers at, and just beneath, the wood surface.
After 24-48 hours the treated surface is dry to the touch and ready for
light sanding or direct application of putty or paint primer. Penetrol
is like a light varnish or like an alkyd resin oil-based paint without
the pigment.
Storm Stain is a waterborne product that contains zinc napthanate and a
very tiny amount of resins. Zinc napthanate is a preservative that
limits mold, mildew and fungus. The resins help hold the zinc napthanate
in the wood, but there is not enough resin to consolidate loose fibers
at the surface of the wood. Storm Stain does not penetrate as deeply as
oil-based pre-treatments because it is waterborne. After 24-48 hours the
water has evaporated , the wood surface is dry, slightly tacky to the
touch and ready for paint primer.
Take care, work safe and keep in touch.
John
by hammer and hand great works do stand
by pen and thought best words are wrought
John Leeke, American Preservationeer
26 Higgins St.
Portland, ME 04103
207 773-2306
[log in to unmask]
www.HistoricHomeWorks.com
--
**Please remember to trim posts, as requested in the Terms of Service**
To terminate puerile preservation prattling among pals and the uncoffee-ed, or to change your settings, go to:
<http://listserv.icors.org/archives/bullamanka-pinheads.html>
|