Hi NorCal Dave and Dusty -I am coming at this from the perspective of a guy who spent a couple years working in a refinishing shop, as well as building furniture, studying and talking with craftsmen and women, and building a few truck beds. Finishing wood can be a lifetime learning process and a lifetime career for some - so here are some basics for oil and oil vs urethanes (polyurethanes, spar varnishes, wipe on urethanes etc) finishes that have worked for me...
Dusty: Seems like you are concerned that the poly will not penetrate and more likely lift or scratch. You are correct that oil finishes will penetrate into the wood and repairing damage to the finish is less burdensome. Poly is a surface coat with light penetration and it tends to lift or flake if the wood becomes damp or the UV rays start to break it down. Scratches and damage that go deep into the wood will be noticeable and difficult to deal with.
Staining pine can be challenging - because the pitch or resin in the pine is uneven throughout the wood. Some areas will absorb the stain and some areas not so well - so there is a risk of it appearing to be blotchy and uneven. I tend not to use stains, but find a wood that is the color I want or go all natural or, topcoat with a solid type of paint rather than staining.
NorCal Dave: To help make the expensive tung oil stretch futher, I mix it with turpentine to thin the oil and allow for better penetration. You can also use a higher grade solvent like mineral spirits and lacquer thinner for faster flash-off when it evaporates leaving the oil. And this isn’t an exact science - throw in some lacquer thinner, turpentine, tung oil. small amount of boiled linseed oil (maybe a 75:25 mix), and for the last coats add some thinned amount of spar varnish or types of urethanes that you can purchase from a boatbuilding catalog and create a brew. Add some oil based stain to this brew/mix if you want to add color - but it’s not needed (for the reasons above). The wood darkens with age and as it absorbs the oil.
Both the boiled linseed oil and tung oil have what is called Japan driers in it - and that’s what allows it to set up and chemically cure. Slather your mix on, let it sit, and then keep slathering it on so the wood will super absorb and keep it wet with your brew. Do this for a couple hours - both sides or faces, then take a wad of rags without lint, or papers towels while it is wet, and wipe it off just as it barely starts to get less than tacky. If it starts to set up no worries… just wet it down again until you can get to the next board and wipe it off. Just keep lopping it on until your final wipe down and overnight sitting.
Give it a day or two to ensure it sets up and dries. Because it is super soaked, the pores may spit out the oil as it dries and you may notice the finish may be rough (if you notice this while its drying just wipe down at it dries) - hand sand with 220 up to 320 or 400 use wet dry paper dipped n your brew, wet the board down and sand the wood with this wet dry paper and oil mix. Wipe off again abd let the surface dry.
For the best of both worlds, after the oil dries off - you can apply the spar varnish over the surface as a thin coat or several thin coats.
You will be amazed at how deep and well protected the bedwood is by giving it the best of both worlds - a penetrating oil and surface protection. To repair - sand with the brew, feather the scratched areas with the brew and wet/dry paper. Wipe off - and blend the spar varnish of the repair area to the other area.
This finish preserves and protects the wood but for how long finishes last depend, as you know on storage, protection from the elements, UV rays, use etc. For a natural, well oiled and very nice looking bedwood this finish will yield very good results. If you plan to keep the truck out in the elements year-round - then you may need to maintain it and reapply to protect it over time or consider a heavy duty topcoat paint.
Last edited by tom moore; 07/08/2022 7:06 AM.
