While finishing my latest quarantine project, my mind began to wander. I was using an oil finish and while waiting for it to soak in I asked myself what would happen if I heated the wood before putting on the finish? I’m thinking hair dryer or heat gun not hot enough to ignite the wood or finish.
I came up with three possible answers.
#1 Nothing changes. No impact; visible or otherwise.
#2 The oil soaks in deeper because the wood pores are opened up by the heat. The result is a finish that looks the same but is deeper and offers more protection.
#3 The warm wood absorbs more oil but as the wood cools the oil is squeezed out of the pores creating a hot mess (pun intended).
Anybody have any thoughts? Experience?
Replies
Some folks warm their oil (in a hot water bath for safety) before applying which they claim helps it penetrate better (no personal experience doing this). I imagine heating the wood would transfer some heat to the oil achieving a similar effect, but probably less so.
If you have open pore wood like red oak, the oil is going to seep out and need to be wiped off repeatedly no matter how you apply it so I wouldn't worry too much about that.
If you want to experiment, I think heating the oil is a lot easier than heating the wood. Just set the can in a pan of already hot water and let it warm up a bit before using. Don't expose the oil to any heat source directly or things will get exciting fast.
I dont see heat as changing the size of the oil molecules, which would be the key to deeper penetration.
BUT I've always questioned the two assumptions here: (1) that oil penetration is significant at all; (2) that deeper oil penetration would be more protective.
I tried applying heavy BLO to several different wood species sanded to varyious grits and then cutting cross-sections after curing. I could not detect any penetration visible to the naked eye at all, at any surface prep, even with thinned BLO. I'd be interested in anyone else's experience. YMMV.
That's my experience - there is no "penetration" by oil finishes. Rather, they form a very thin coat of whatever they contain in the way of a solid, left solid after the oil and thinners evaporate.
There are endless studies that show that this is the case - no penetration, just a film. Open pore timbers do take more oil into their teeny pits, which take longer to dry and so seem to exude oil. I fact, they're just leaving a thicker area of the solids in the pits. We wipe these when semi-dry to blend them with the already dry areas to get a smoother look rather than the shiny wee flecks over the pits.
But to answer the OP's question (after a fashion):
Long ago I applied an oil finish (Liberon Finishing Oil) outdoors, to a cherry table I'd just made. It was too smelly indoors on a hot day. I'd already taken to wiping on very thin coats with a cotton rag - or even a very fine grade sanding sponge - rather than sloshing it on and waiting for a while before wiping off the excess. The sloshing method just seemed wasteful.
I found that thin, rag-applied coats dried faster and resulted in a much smoother finish. Using a fine sanding sponge (800 grit or more) to apply the oil also produced an eventual greater shine than the usually more matte finish from wiping with a cotton rag. It also filled open pores with a dust/oil mix that worked like a more conventional filler.
But perhaps the greatest revelation on that day of outdoor finishing was that sunshine and open air on the thin finish layers speeds up the drying a great deal. As long as I rag-wiped or sanding-sponged as the thin layer dried, it would be smooth and ready for the next coat in a couple of hours or so rather than the next day.
So, if there's a windless and rain-free sunny day available, I always do this with an oil finish now. Heat does speed the process (as you'd expect with any chemo-physical process like this) and the result can be controlled or "kept good" by careful attention with the wiping/smoothing rag until its dry and ready for the next coat.
Too much sun is probably risky as it'll go tacky in no time, preventing the smoothing-wipes. And the coats do have to very thin, not sloshed-on. But it works.
Lataxe
PS I don't use anything other than the oil finish - no six layers of mysterious pre-this or post-that. The oil is enough all by itself to give a very good finish, matte or shiny depending on the amount and how you wipe each layer as it dries. KISS.
My first rule to finishing is read the instructions and break no rules from this point forward.
Second• Do a sample if it is your first or second time applying a new product. If you are going to deviate from the instructions or add your own new step, do a sample.
Third•. Assume the company who made the finish used Empirical research methods to make their product and wrote instruction that will work well.
Forth• Preparation is crucial for a good outcome.
Fifth•. Keep a diary of the temp, humidity, viscosity and anything you can think of.
Good post..
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