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sealing
Regular boatbuilding laminating epoxy is not thin enough to seal, it has enough viscosity to hold in the cloth and with brushing will wet out the glass cloth. When you seal wood, you are trying to get some protection as deep as you can.
Hardwoods are biologically constructed with pores(ring porous (oak), semi ring porous(ash) and diffuse porous(cherry)) which make them good candidates for most sealing applications, particularly in the area of the end grain, as the pores can conduct the sealer into the wood. Soft woods contain no pores and usually some type of protective resin. There can be some absorption into the end grain but the sealer has to fight the resins. Sealing on softwoods is usually a surface protective coating. In the case of using this sites favorite sealer 60/40 BLO and thinner, in my opinion, works on softwoods because the thinner in the mixture will cut the resin and the BLO will take its place, on hardwoods the thinned BLO is pulled along into the pores with the thinner (capillary attraction).
When you seal with epoxy, the epoxy is mixed at it regular ratio and then thinned (xylene), this effects the set up time of the mix and its strength, but allows via the thinner, its aborption into the wood through the pore in hardwood, and by reducing the resin in softwoods. Some softwoods don't need sealing (cedars, cypress), their resistance to the weather are well documented. Pine if kept out of the dirt is very durable. The oldest timber frame house in America, The Fairbanks Morse House, in Dedham still has it siding and frame. I don't know about the old plugs, there are builders here would have more knowledge than I have, but I would be willing guess the sealer they used, if they sealed them at all,along with the paints contained either a linseed base or an oil base as the vehicle in the paint. Back then the top coats more than likely contained lead. All in all apretty good protective coat. Sorry for the long post
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