MIMF

Sorry to keep asking naive questions, but I'm planning my second build.
Is Penetrol by Flood potentially useful on a guitar? It is an oil and varnish (I think?) product that hardens. I've used it on bare metal and to renew some oak cabinets. It seems to soak in and build up slightly, and shines very nicely. Since I already have enough to cover several guitars (a little goes a long way) I wondered if anyone can tell me if its a good or bad idea?
If it's not a viable body or neck finish I also wondered if it would work for rosewood fingerboards?

I'm sorry, I meant to post this inquiry in Glues & Finishes.

Most likely it is bad. Oil soaked wood generally makes a soggy sounding guitar. Aside from being mostly naphtha, the oils are boiled linseed and a long oil alkyd resin, neither of which dries particularly hard.

For a neck it might be O.K., If you like an "oil" finish on the neck, but I think a finish intended as a top coat might be better. My understanding is that Penetrol is usually used as a base coat for oil base paints.

The more I think about it, the less I like it. Just the thought of the spruce sopping up finish...no thanks.

But if these are going to be your guitars, why not try it on one?

Just another one of my not-so-great ideas. Thank you for setting me straight, guys.

Dave, try some on a prepared surface on some scrap material, and let us know how it works. It might be the next hew thing, or not. If you want to know how hard a finish dries try it on a piece of glass and let it dry for a good while. If it gets hard it will chip when scraped, if it stays soft it will be a bit gummy when it is scraped. And anything that soaks into wood will probably leave a blotchy appearance because wood seldom has an even distribution of grain. It soaks into end grain and is resisted by side grain.

Do a side-by-side test: take a piece of scrap of your intended instrument wood and give it a coat or two of the finish; take another scrap, give it a splash coat of shellac, then apply the finish as with the first; maybe try a third with an epoxy seal. After a good while, cut both pieces in half and see, if you can, how far the finish penetrates (might be something you smell). Even with True Oil, which is a go-to finish for many, I've seen a lot of recommendations here for a seal coat of shellac first.

The other issue is repairability. If it's a penetrating finish, you can never get rid of it. The beauty of common instrument finish is that it's on the surface, pretty much, and can be worked with in repair situations.

I've only ever used Penetrol as a paint additive, it helps oil paint lay down smoother when applied by brush or roller basically. I've never thought of using it as a finish by itself. Really, there are plenty of finishes out there that I don't understand why you'd use this. I've used Tru-oil several times and really like it.

I did a test. It's a no go: If you put it on heavy enough to shine it takes too long to dry, and when it does dry it is too soft. Same results for one heavy coat or multiple thin coats.
I still think a quick wipe on/wipe off might work well on a rosewood fingerboard but I don't have any scraps to test and I'm not willing to experiment on my guitars.