Food Safety and Wood Countertop Finishes

      Objective information about wood finish safety for contact with food is hard to come by. August 27, 2012

I am getting ready to finish a large redwood crotch for a kitchen countertop, and want to know the best finish to use that would be non-toxic to food. Will not be cutting on it like a cutting board. Any ideas?

Forum Responses
(WOODnetWORK Forum)
From contributor P:
Salad bowl finish. Wax on, wax off.

From contributor C:
Waterlox Tung Oil. Looks great, easy to touch up. But use anything you like. Why not a floor finish? Solvents flash off in drying. No chance to mix food with finish. What do others think?

From contributor G:
I'd be concerned about dirt/bacteria getting lodged in open grain. Filling the grain - perhaps with a contrasting color - would make a smoother, more easily cleanable surface. You don't want your customer scrubbing it with a bristle brush. If you go the tung oil route, you can sand in the first few coats, which will fill the grain also.

From the original questioner:
I used a tung oil mixture on some oak window seats, sanding it into the work - good idea. So what about this filling the gain with a contrasting color?

From contributor G:
Decorative grain filling isn't too difficult. In many cases, the wood is stained and a contrasting colored filler is used (i.e. black stain/white filler), but I get the sense that you want to stay with the natural colors of the oak.

Choose the color you want for your filler.
Choose the type of filler you want to use. The staff at your finishing supply provider may help you pick one and can probably even tint it for you.
Clean out the open grain with a brass-bristle brush and compressed air.
Thin your filler to the consistency of ketchup and spread it evenly over the oak. Try to get it pressed down into areas of open grain.
Remove the excess with a stiff squeegee and/or a burlap rag. Careful to not drag filler from the grain - work cross-wise.
Allow to dry at least overnight and 24 hours is better. Some of those grains can go deep.
Sand the whole thing to remove any unwanted color from the high areas, leaving the color in the low spots.
You should now have a level substrate. Make sure the topcoat you use is compatible with the filler.
PS: If you choose a water-based filler, seal the wood first to help prevent cupping.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Can someone give me a reference that says tung oil is safe for food contact? Thanks.

From the original questioner:
Have not heard of any article for tung oil being safe for food contact. I am not using it; I generally use it on furniture, etc. Have heard of an epoxy formula for using on countertops, but is appears too glossy for me.

From contributor G:
After the solvents have evaporated, pretty much any finish is food safe for casual contact. For use on a cutting board, you'd want a non-film finish so you wouldn't be eating chips of finish flaked off (not that they would be likely to hurt you any more than any other minute scrap of plastic you might ingest).

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Some finishes may have the solvents evaporate, but the finish is soft and/or oily. I think contributor G might have been more accurate to state that hard finishes are safe... But unless someone can show that this is really true, I would be very careful.

From contributor G:
Which finishes are you thinking of that are soft or oily that you have concerns about, Gene?

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Shellac, wax-based (not all bees wax) are two.

From contributor G:
Am I understanding correctly? You are concerned about the use of shellac and wax such as carnauba in food environments?

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Yes, some waxes do not get hard and some oils do not get hard and may not be safe to eat. Some other finishes, such as poorly cured urethane finishes or shellac, can be soft and unsafe to eat. Hot food may soften such finishes. A knife can cut soft finishes (hot or cold) and leave a scratch that accumulates bacteria. This scratch and bacteria was studied in plastics by the Univ of Wisconsin some years ago.

From the original questioner:
Okay, so what type of hard finish would be best for use on a counter top that will come into contact with food?

From contributor G:
As I pointed out, casual contact with food is no problem with almost any coating. I can't think of one offhand that I would consider unsafe. Molecules of finish don't jump onto food that touches them. Using it as a cutting board is an entirely different matter.

To address your concerns, Gene, shellac, although thermoplastic, is considered a hard coating (as opposed to spar varnish, a flexible coating). Shellac is used in the food industry as a shiny coating and in the pharmaceutical industry as an enteric coating.

This is from an article by Jeff Jewitt on shellac:
"It is approved by the FDA as a food safe coating when dissolved in pure ethanol (not denatured)."

Carnauba/paraffin emulsions have been used for decades as fruit and veg coatings to prevent water loss and shriveling. Paraffin wax is used on home preserves as a sealer.

I agree that improperly cured urethane, or any other improperly cured finish isn't safe, but who would flop down a slice of bread for a sandwich on a sticky counter?

To the original questioner: the best coating for your need depends on the expected use of the counter. If it is near the sink, for instance, you may need a different finish than if it is just for a prep area. Will it have hot dishes set on it? Do a Knowledge Base search for wooden counter finishes and you will find everything you need to know. Don't forget to finish top and bottom equally, to prevent cupping.

From Professor Gene Wengert, forum technical advisor:
Contributor G, you state "with almost any coating..." Which coatings should be avoided, do you think? Casual contact is not an issue. What is your source for this statement please? People talk about FDA approval for food safe coatings. Is there one site that indicates the coatings that are approved?

From contributor G:
I had this discussion a couple years back with one of the old school finishers. We went back and forth for days in the Finishing Forum. What it boils down to - there is no specific requirement for any finish to apply to be deemed food safe, as the ingredients that go into the finish (and remain - solvents don't count) are already classed as food safe (such as the oils that go into varnishes) and any dangerous components (such as lead) are already banned.

I phoned a paint chemist at Chemcraft. He came into the forum and said that although finishes are inherently food safe, no manufacturer is going to label their product that way because there is no requirement to and there is no regulatory body to issue an approval.

Coatings that I would consider unsafe for sure would be creosote, anti-fouling boat hull paint such as tributyltin fluoride or any type of non-drying organic oils or animal fat, both of which will go rancid.

As to the "casual contact" statement, my source is common sense and my knowledge of how paint dries. Particles of finish just don't detach from the film to migrate to your food. If you have any source that directly contradicts that, I would be glad to hear of it. What finishes would you be wary of allowing your sandwich to touch?

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Thanks for the clarifying comments. So, if I understand you, when people say that a coating for a wood counter top is FDA approved for food contact, that is not true? The FDA does not approve coatings for this use? Do they approve coatings for cutting boards?

From contributor G:
I'm in Canada, Gene. I don't know how the FDA works.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
One other concern about countertop coatings is that they must be able to withstand short term heating (such as when someone puts a hot pan on the top). I hope someone can locate a statement or web site from the FDA that indicates what countertop coatings are approved.

From contributor G:
We advocate the use of trivets or insulating pads. Few, if any, coatings manufacturers will warrant their product if hot pots are going to be set on them regularly.

From contributor C:
FDA posts a list of GRAS "Generally Recognized as Safe" products for inclusion in food. For example, carnauba wax is included among other oils and waxes. Since we don't wish our finish to end up in food, we probably are not worried about the GRAS list except for perhaps cutting boards and salad bowls.

The FDA also has a list for Food Contact Substances (FCS). There is a searchable database of information. If you search "varnish," nothing will come up, but if you search resin or rosin, you'll find something.

In my opinion, the FDA is giving lists of chemicals that can either go into, or come in contact with, food. I do not think the FDA is looking at complexes of these chemicals as would be found in our finishes. But since we do not expect our finishes to end up in food, it is likely that we do not have a food safety issue here. Just my opinion though.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Thanks for the info. If someone has a countertop and subsequently develops an illness (even lung cancer and even if they smoke), it is indeed possible that they will look for causes of this or another illness. If the coating used on the counter has some risk of being unsafe and causing a disease in animals, etc., they will add the provider of the countertop to their list of people that they are suing. (I have seen lawsuits where the presence of a small piece of asbestos (about 2"x2"x 1/8" thick inside a machine) has made the company part of a lawsuit regarding lung damage. Therefore, although you may believe that the coating you are using is safe and the contact is insignificant, it is important to use a coating that is generally regarded as being safe in order to avoid such legal action. I suggest that most of us cannot avoid defending a lawsuit (or our insurance company will not want the cost of defending) or doing the research to show that our coating system is safe. We can complain about the unfairness of such a legal system, but it is reality today in the U.S.

From contributor C:
Gene, I understand your point. I have to wonder though, if it's safe for floors and it's safe for cupboards, and it's used on baby cribs, and so on, what is the difference with countertops? Food contact? Babies chew on cribs, actually eat it. We know we need to be lead free. We are not finding a regulation that connects what we do with food safety. The FDA specifies levels for GRAS and food contact, but more for packaging, cooking and commercial food preparation. For instance, the FDA might say a product can include up to 1/2% shellac ( a common ingredient in confections), in the actual product. How much shellac could food pick up in casual contact? Probably none. Should we be worried about potential liability on this one? I'm not sure. I carry product liability insurance. I don't want to get worked up about it beyond that because there is enough to get worked up about - economy, staffing, bills, production, quality, etc. Contributor G had a good response about regulatory bodies, although we aren't sure if the US is more or less strict than Canada on this, but that is beside the point if countertop coatings are non-regulated, which appears to be the case.

From the original questioner:
So after much discussion… Red oak will be used as a kitchen counter, close to the sink. Main use would be to set plates, drinks, food containers, etc. on. What would you coat the surface with?

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Whatever the coating is, it must be 100% waterproof. If any water gets through and there is any iron, the countertop with develop iron tannate stain, a blue-black color.

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