The information you found is true, and I congratulate you on become a better educated consumer. For some reason wood finishing is full of myths and mistruths - "tung oil finish" that doesn't actually contain tung oil is a perfect example. I've seen other examples on this forum as well, and think it's a shame that people are being mislead by improper labeling.

If you want to learn more about wood finishing, the two best-known authors on the subject are Jeff Jewitt and Bob Flexner. I've never read Jewitt's books, but Flexner does a great job of cutting through the myths and accurately describing the facts and science.

The point that a "tung oil finish" doesn't have to contain any tung oil and can contain many other things as well including substances you wouldn't want to prepare food on is correct.

The generalizations aren't, though, and some of the information is just wrong.

Pure tung oil soaks into wood and over time dries by polymerizing - the molecules bond to each other and become stronger. Heating the oil before it is applied causes some or all of the molecules to join up so that they're too large to soak in and voila, you've got a varnish because "varnish" simply means that it dries on the surface of what you're applying it to. The polymerized substance can also be called "resin". (also "boiled linseed oil" isn't really boiled, it's just mixed with a solvent which causes it to dry like other oils do when they've been heated.)

Waterlox, according to their website, is a combination of "resin" which could be anything including cooked tung oil, pure tung oil (to soak into the wood) and solvent to keep it thin and liquid.

For me, for food surfaces I want either pure tung oil - the wood is protected but nothing builds up on the surface - or a mix of pure tung oil and a varnish (aka resin) to soak into the wood as well as build up on the surface for extra protection. And I don't want any toxic metallic driers in it. So I use pure tung oil thinned with citrus solvent on my chopping surfaces and pure tung oil followed by thinned Waterlox on surfaces that food will be on.

As you found out, Minwax Tung Oil finish is pretty, but not tung oil at all :)

Q for mondragon or chifneil or any other informed individual:

is it safe to have mineral spirits or a mineral spirits derivative on a butcher block where presumably comestibles may be processed (cut, dried, spread out, slathered) or or consumed? I thought mineral spirits based wood products were okay for general furniture but not so much in the kitchen. Could you please expostulate and clarify - I'm frequently befuddled on this point.

Thank you.

I was actually reading an article the other day saying that no wood finish has actually been officially FDA approved as food safe. However they're all generally considered safe lacking evidence to the contrary.

Anyway, here's what Flexner says about the food-safety of driers (and presumably this applies to mineral spirits as well).

"Salad-bowl finish is simply a wiping varnish. The implication in the name is that it is safe for contact with food and for small children who might chew on the finished wood. It is safe of course, once it has cured, but so are all the other available varnishes and wiping varnishes.
The safety concern is the metallic driers used to speed the drying of the finish. Lead was once used and it isnÂt safe. But lead isnÂt used anymore. It takes several driers to replace the lead, and there are only a few driers available. So all varnishes use essentially the same driers. There is no difference in the safety factor of any of these driers. All are safe.

ItÂs amazing to me how the food-safe myth continues to be repeated in woodworking circles. (And more amazing still that salad-bowl finish is considered safe while the other wiping varnishes arenÂt!) Food safety is a non-issue. All finishes currently available to woodworkers are safe to eat off of or chew on once the finish has fully cured. Curing occurs faster the thinner the film and the warmer the surrounding air. Press your nose up against the hardened finish and take a whiff. If you can smell anything, the finish isnÂt cured. Give it some more time."

Here is a link that might be useful: Flexner article on varnishes

I would like to know about food prepping safety as well. My block top will be used mainly as extra counter space, and "hopefully" no chopping. If the tung oil "finish" is not safe for food areas, can my minwax tung oil "finish" be toped by a compatible finish. Like maybe the waterlox or some other bullet proof product 0r pure tung oil????

chiefneil, gosh, thanks so much for digging up the answer. I ran through the article but I'd like to read the full article in a lot more detail - loads of good information there. Thanks a lot. Sounds like mineral spirits at least are not a consumption problem once "cured".

Ok, another uneducated question for you spawned from that article - is polyurethane a mineral spirit or is it a different article altogether?

Mineral spirits - like citrus solvent - are used because they evaporate, supposedly leaving behind just the substances they were used to thin, like oil or varnish. The danger with solvents is with inhaling the vapors while they are evaporating. My guess is that they leave behind some residue, the question is if the residue is both toxic and in sufficient quantity to have an effect.

Driers are chemicals added to a varnish to make it harden faster. Used to be lead, now seems to be much less toxic (or non-toxic) substances.

Polyurethane is another kind of varnish. Some polyurethanes are water-based instead of oil-based so they don't need a solvent.

The question is if it's safe to prepare food on a surface that's been finished with a modern solvent-based varnish like Minwax Tung Oil finish. My personal belief is that once it's dry (and the smell test suggested in the article chiefneil linked to is good) that a good washing with soap and water is going to remove the vast majority of anything that could come off with contact with food and anything that did would be in such miniscule amounts as to be no risk. Think about all the plastic food packaging our food is in contact with, anything I'd get from a counter top wouldn't even compare.

Why not use mineral oil. It's available everywhere, is cheap, you don't have to worry about special additives being put in it, mis labeling, this brand or that, someone having an allergic reaction to it, oh and IT'S safe for food contact wet, dry, and in between.

Basiclly - use MINERAL OIL on cutting surfaces. It ends the wondering, confusion and discussion.

Sutherland Welles polymerizes Tung oil to make it a better bonding, protective, and natural finish