Is epoxy food safe? What “food safe” really means for resin

The short answer

Uncured epoxy is not food safe — the separate resin and hardener are reactive chemicals, and that is why you wear gloves. Some fully cured epoxies are sold as suitable for food contact, usually with a statement that the cured product complies with the US FDA regulation for resinous and polymeric coatings, 21 CFR 175.300, or that it has been tested for migration. ArtResin, for example, says its product is safe as a food-contact surface when it is measured and mixed according to the label and allowed to fully cure.

The important words are “when” and “fully cured”. The claim applies to a correctly mixed, completely cured coating used within the limits the maker states — not to every piece that has been poured with that product.

What 21 CFR 175.300 actually covers

21 CFR 175.300 is the section of the US Code of Federal Regulations for resinous and polymeric coatings used as food-contact surfaces. In outline, it:

• lists the substances such coatings may be made from;
• requires a coating meant for repeated food contact to be applied as a continuous film that acts as a functional barrier between the food and whatever is underneath; and
• sets limits on how much of the coating may be extracted by food-simulating liquids under specified times and temperatures.

The regulation doesn’t approve individual brands. A maker that says its epoxy “complies with 21 CFR 175.300” is stating that its formulation and the cured film meet those conditions. That is the manufacturer’s claim to stand behind — which is why you should read it on their own label or data sheet rather than on a reseller’s listing.

Four conditions that make or break the claim

1. The exact mix ratio

Epoxy cures by resin and hardener reacting in a fixed proportion. Too much of either leaves unreacted material behind, and an off-ratio coating is no longer the material the maker tested. Measure exactly, by volume or weight as the label states — the mix ratio calculator converts between the two — and mix for the full time.

2. A full cure

Dry to the touch is not cured. Most coating epoxies take several days to a week to reach full cure at room temperature, and longer in a cold room. A food-contact claim assumes the full cure time on the label has passed. See how long epoxy takes to cure.

3. An unbroken film

The regulation is about a continuous coating. A cut, chip or deep scratch exposes whatever is underneath and breaks that barrier. That is the main reason an epoxy surface is a poor choice for chopping on: knives cut into it, and the grooves are hard to clean.

4. Temperature and contact time

Cured epoxy softens with heat. ArtResin, for example, rates its cured resin to about 120°F (50°C) — fine for a cold drink, not for a pan straight off the stove. Hot, fatty or acidic foods left in contact for a long time are the hardest test for any coating; follow any limits your manufacturer gives.

Common projects

For planning a serving board, the river charcuterie board example shows how little epoxy a small board takes; for a full counter, see the 50 sq ft kitchen countertop.

How to check a product before you buy

1. Find the technical data sheet and safety data sheet on the manufacturer’s own site.
2. Look for a specific food-contact statement: which regulation or test, and under what conditions (full cure time, temperature, type of contact).
3. Note the mix ratio basis (volume or weight) and the full cure time — the claim depends on both.
4. If the statement is vague (“non-toxic”, “safe”) or missing, ask the manufacturer directly or choose another product.

Also note that “non-toxic” on a label usually describes the product’s hazard classification for handling, which is a different question from whether the cured coating is suitable for contact with food.

Using a food-contact surface day to day

• Let it reach full cure before first use, then wash it with warm soapy water.
• Hand-wash; dishwashers combine heat and long contact.
• Use trivets for hot pans and a cutting board for knives.
• Retire or recoat pieces that are deeply scratched or chipped.