Niles Canyon Railway has a single-sheathed ("outside braced") automobile car, ATSF 313612. This is one of the boxcars that had the roof raised circa WW2 to accommodate aircraft parts and automobiles. The wood siding is very dry, and most of the paint has disappeared.

The wood needs to be protected against the weather as much as possible. What sort of paint is the best choice here? Something that penetrates and protects the wood would be great. We can use whatever is best: oil-based, or latex-based. (I'm hoping the paint can be applied by airless spray gun, but other methods are OK too.)

Thanks! - Doug Debs

I would suggest clear polyurethane thinned 50% (not water-based) and then applied with the airless sprayer. Probably a good idea to apply a second coat, if the wood is really dried out. It should go on quickly with the usual airless equipment! Once that dries, apply a good oil-based topcoat paint. Stay away from latex-based stuff. We have found that polyurethane mix penetrates old wood and new wood very well, much better than any of the currently available primers.

We have not used linseed oil for rehabbing old weathered wood, and I do not claim to be a wood-worker. Just passing along our experience with the poly stuff.

Howard P.
RMNE
Thomaston, CT

Smith's Clear Penetrating Epoxy Sealer is being used for this purpose on the portable rotary converter car (Sacramento Northern 1) at the Western Railway Museum. (Actually we're replacing the siding, but this product is being used to stabilize some of the studs and timbers which are not being replaced.)

The company's web site:

http://www.smithandcompany.org/CPES/

My own preference (for architectural historic preservation) is to use one or more applications of THINNED primer, which can contain some material like fungicide or biological preservative. I apply thin coats and let them soak in until the wood shows 'wet' and does not take up more of the material. This ensures that the wood structure is completely penetrated not only by the vehicle but by a workable percentage of the actual 'restoring' and preservative content, which unthinned coatings won't do, and also that no dry cores remain to make an applied paint film easy to separate.

My training was to use a solvent-base material rather than water-base for this, but this was back in the late '80s. I suspect that a consequence of low-VOC laws is that at least some modern water-base products will have adequate penetration but not result in too much 'trapped' water content to cause problems with subsequent overcoating. (On the other hand, ISTR that the good water-base products are 'substantially' more expensive than solvent-based alternatives...)

Low VOC is here however if you are out of the LA basin you can get 250 voc instead of the zero voc. Paint thinner in CA is now some concoction of acetone, you can not get the real paint thinner any longer.

Polyurethane or spar varnish would be good thinned 50% so it can penetrate however the first coat should be brushed on and in fact with firm bristles to scrub it into the wood. Subsequent coats can be sprayed. Generally when doing this process start at 60/40 thinner/poly then each coat changes by 10, 50/50, 40/60. 30/70 and you should be good.

The penetrating epoxies are very good as they add strength where the wood fiber has broken down.

You definitely want to use a 2-part chemical. You want it to penetrate deeply, and then you want it to cure. 2-part products can cure after penetrating, because they self-cure - time alone will cure them. 1-part products need to interact with air to cure, and air can't penetrate more than a few mils, so it never reaches the penetrated paint. So it doesn't fuse with the outer coat, and the outer coat can pop off.

I will second this! I use CPES all the time in the marine industry. You can use it to stabilize rotten wood, or use it as a sealer/primer for new wood. It seems to accept almost any paint over top of it (I have not found one yet that didn't jive), and in most cases, you can use it over stain and put urethane, varnish or other clear on top. In most cases, if you use a good quality top coat, you will not need to prime before painting. I primed my 1963 Thompson with CPES and was able to build 3 coats of Easypoxy directly over it. I could tell right away that the paint was bonding well.

Perhaps it should be mentioned that. I believe, some "other" 2-part penetrating epoxies are in fact the Smith product, repackaged with the price raised. For the amount of product needed to do a car with dried and open wood, this might involve a significant cost difference ... so research well and choose your supplier wisely.

I've used CPES and Epifanes varnish to finish brand-new outdoor furniture, following a technique that was in an old issue of Fine Woodworking. A quick search shows that the article is posted on their members-only website, with a summary visible to non-members: A Durable Exterior Finish - Epoxy sealer and marine varnish protect wood against the weather

Has anyone used that technique for new wood benches in an open car or new outdoor seating at a depot?