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

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