The Arbatron instructions call for thinning with acetone. I tend to follow instructions closely when using products like epoxies... The manufactors know much more about their products than I do...

Every epoxy system is a little different from the next. I am sure that if Abatron suggests that Acetone is alright for thinning then it is. I used generalized information on the discussion of epoxies. Copied below is the paragraph.

Does thinning epoxy make sense? In some situations, thinning is appropriate. In others, it is not. We feel that in most circumstances using heat to thin epoxy is preferred to using solvents. As long as the epoxy does not overheat during cure, the full physical characteristics of the cured epoxy remain. Adding solvent is a quick, simple method of thinning epoxy, but the strength and moisture resistance of the cured epoxy are signiflcantly reduced.

So generally this is true but maybe not applicable to all systems.

It looks like people are using epoxy for two different purposes here: The thinned epoxy for deep penetration as a anti-fungal compound, where strength is of secondary importance, and "neat" resin to replace or solidify damaged wood. I'm not sure that thinned, catalyzed epoxy resin makes the best anit-fungal, but it does have the advantage of being totally compatible with later applications of full strength epoxy.

When I got into this hobby in the early seventies at IRM, EVERYTHING was given a coat of PENTA as a matter of course. New wood, old wood, old wood that remained after parts were chopped out for dutchmen, it was just an article of faith that the addition of some rot preventative compound to the existing fabric could do nothing but good. Heck, the rumor persisted that Penta could even make Nick's infamous "green weenies" edible again, although I never tried.

The thinking has some merit. No matter how well sealed we think we have the wood, water will find a way in. Even cars stored indoors are subject to an occasional trip outside in the rain, and in the mid-west at certain times the carbarns are humid enough to make the steelwork on the cars sweat, and this moisture is going to run right into the joints that take it deep into the wood. My overriding concern would be to make sure that there is something in the wood that would keep the fungus colonies from becoming reestablished, even if the moisture content reached a level that would support rot.

Thinned epoxy aside, it seems that we have three preservatives still available to us: copper napthanate, ethylene glycol, and boric acid.

Copper napthanate is an oily material. Someone said that heavy enamel should cover it, but I've not found anything that claims that the paint will stay adhered without blistering over time. It does not seem to be suitable for use under epoxy repairs, due to potential adhesion problems.

I followed the links to an interesting discussion of boric acid, glycol, and mixtures thereof, see:

http://www.acbs-bslol.com/Gadgets/D97WoodRot.htm

Interestingly, the product I first asked about, Bora-Care, turns out to be a premixed solution of boric acid in glycol. See:

http://www.nisuscorp.com/pdfs/boracaremsds.pdf

I note that the instructions indicate that Bora-Care is to be mixed with water, which then has to dry before any further repairs can be done. The thought comes to mind that all or part of this water could be replaced with methanol, or acetone if flammability is an issue, for both deeper penetration and faster drying. In addition, if there is some question about epoxy or paint adhering to the treated surface, these solvents should remove any residue, or wash it deeper into the wood.

It would seem that one advantage of the boric acid treatment is its solubility in water; even if it doesn't initially suffuse entirely through the wood, any moisture entering later will cause it to migrate further, so wherever the moisture goes, it won't be able to support rot fungi. It would seem that it is worth getting some sort of borate treatment into the wood before it is sealed with epoxy for this reason alone.

We have used both Bora-care and a home made copy. They came highly recommended by one of the care folks at the Maritime Museum at Hyde Street Pier in San Francisco. Apparently, at one time they had a lawn sprinkler running inside the hull of one of their wooden ships, with a sump pump to recalculate the solution. The solution is toxic to the fungus which causes dry rot, which by chance is the same or similar to the fungus found in the digestive track of termites, which allows them to digest cellulose.

We have found termites in the deck of a wooden flat car. We applied bora-care generally. It seemed to kill them, with minimal negative effects other than a light salt stain. As noted it is water soluble, and does need to be reapplied annually. We apply it with a standard garden sprayer, reserved for that use.

With a collection of wooden cars, currently stored outside (new building soon!) we use a variety of things to keep them from rotting and deteriorating. We have more than one car witch has seen Bora-care, copper green and epoxy… within a short period.

A couple things to add to the mix. We had a rotten main beam in our snowplow. This is the beam that has the coupler on the rear and goes thru the carbody to a pin under the front of the plow. When bucking snow, this beam takes all the buffing forces rather than the carbody. The beam was about 1/2 rotted away from the top down, just to the rear of the front pin. The beam is about 14 inches square. We removed most of the powdery rotted wood which left a large hollow in the beam. We sealed the outside sides of the beam and poured a couple gallons of liquid epoxy (Abatron), starting with a slightly thinned mix. Into this pool of epoxy we mixed oak shavings in long slivers, for strength - and less epoxy. The beam has been in service for about 15 years and has seen some very rough service. It is still doing fine.

I live in an 18th century farmhouse and have used Abatron for 20 years. The main trick I have found is to mix up a thinned batch of the liquid to ensure that it soaks in thoroughly. I usually mix a ball of the putty at the same time - while the liquid is sitting in the can for the requisite 10 minutes. I soak the area in question and then immediately start to apply the putty. This mixes with the liquid and forms a past that is thicker the farther it is from the liquid. It is essential that the interface between the wood and the epoxy be well soaked and be mostly liquid. The putty alone will pull away from the wood. I just did structural repairs to some large barn door frames that were rotted at the bottom. After jacking in place, I used the epoxy as described to build up the bottom of the frames. It worked very well.

At the railroad we use all sorts of combinations of putty, paste, and liquid and have saved ourselves tens of thousands of dollars over the past 20 years.