Polyurethane is one of the best materials to use as a coating to seal, protect, and beautify wood. It offers a contemporary polished look and a luxurious finish. When applied to cabinets, dining tables, and chairs, it creates a protective layer that guards against stains and scratches. But what happens when we have to prepare and eat food from surfaces sealed with polyurethane? It looks great but is polyurethane food safe?
According to the FDA, polyurethane in its cured state is a food-safe coating. However, you should only use polyurethane on surfaces not subject to sharp edges or scraping actions that can damage the coating,exposing food being prepared for consumption to contamination.
In this article, we’ll explain why polyurethane is considered a non-toxic, food-safe finish. We’ll discuss when and where to use polyurethane for food safety. We’ll even offer recommendations for the best sealing products.
Contents (Jump to Topic)
- Is Polyurethane Food Safe?
- Is Polyurethane Toxic When Dry?
- Is Polyurethane Safe For Cutting Boards?
- Can You Use Polyurethane on:
- Is Varathane Polyurethane Food Safe?
- What Is The Best Food Safe Polyurethane?
- Final Thoughts
Is Polyurethane Food Safe?
Polyurethane dries to a hard finish that resists damage from abrasions, water, and cleaning solvents better than other traditional varnishes. However, when trying to decide if your finish can make contact with food, there are a few things to take into consideration.
In its raw state, polyurethane is a liquid plastic-like resin containing volatile organic compounds (VOCs) and an isocyanate known to be a toxic respiratory hazard. They can cause breathing issues such as asthma attacks and bronchitis. It is especially harmful to young children and those with respiratory problems.
Polyurethane goes to work when its molecules react with oxygen and form tight bonds. Over time, those bonds produce that highly sought-after hard finish. When done, the hard, smooth film is considered inert and safe for contact with food.
Food Safe Vs. Food Grade
It’s important to understand the difference between a “food safe” finish opposed to one that is “food grade”.
Food grade material is a substance that can come into direct contact with food and is considered non-toxic and safe for human consumption. Examples of food-grade finishes include beeswax, or natural oil-based products like tung, mineral, or walnut oils.
A Food-safe material is a product that can come into contact with food but pose no food safety hazards. A food-safe finish must withstand the purpose for which it is designed. This means other factors such as exposure to heat, scratching, or cleaning solutions must also be considered.
Food & Drug Administration Perspective
The Food & Drug Administration (FDA) recognizes polyurethane as food safe for food contact surfaces. That means polyurethane finishes are safe when used as intended for your food processing applications. When fully dried and cured, polyurethane is non-toxic and non-allergenic in the eyes of the FDA.
Use In The Food Industry
Food safety in the food industry is heavily regulated by the FDA. It also has a long history of success and trust in using polyurethane films and coatings.
The chemistry of polyurethane is so well researched, that its formulations are now used as coatings for food processing components in machinery. It can resist harsh environmental factors such as exposure to high heat, cleaning solvents, oils, and acids.
Is Polyurethane Toxic When Dry?
It’s important to remember that the liquid form of polyurethane with its isocyanates and VOCs, is toxic until it has properly cured. Just because your polyurethane finish is dry to the touch, doesn’t mean it is food safe yet. A “dry” polyurethane coat can remain toxic until it has had enough time to fully cure!
So, how can such a volatile concoction of chemicals be tamed to such a degree that it can be trusted around the food you eat?
Drying & Curing
Once your polyurethane has been brushed, rolled, sprayed, or wiped onto your wood surface, there are two final stages remaining: drying and curing.
Drying is the process of waiting the recommended amount of time before applying your next coat. Depending on the type of polyurethane used, you could be waiting 30 minutes up to 4 hours for each coat to dry.
It’s easy to think your project is done and ready for use once your final coat of polyurethane has dried to the touch and is no longer tacky or sticky. That dry polyurethane has not yet hardened. If weight or pressure gets applied too soon, the structure will be damaged and you’ll have to start over from scratch!
Curing is the process of waiting the manufacturer’s recommended amount of time for all the chemical reactions to complete.
Polyurethane molecules react with oxygen. The reactions are extremely active, and gases continue to vaporize. This is where the hardening of the surface occurs. Depending on the type of polyurethane used, temperature, humidity, and thickness – hardening can take place between 1 and 30 days (or longer). Polyurethane is still considered toxic until the cure time has expired.
When Is Polyurethane Food Safe?
When the recommended cure time has elapsed, you can be confident your project is food safe. Give a final sniff test. If there are no lingering vapors or fumes and you feel a tough finish, you can start using your project as intended.
Is Polyurethane Safe For Cutting Boards?
You never want to apply a polyurethane finish to a cutting board for a variety of reasons. To be “food safe”, the finish on a cutting board has to withstand constant cutting, scraping, and banging. Sharp knives and other utensils eventually cut into, loosen, and break off tiny bits of the finish. Those pieces are now food safety hazards since they are likely to be ingested.
Your board is no longer food safe because the finish is being used in an unintentional way. A sharp knife can cut through cracked, broken, or loose polyurethane and into the wood surface. Bacteria and other types of moisture can become trapped underneath the coating and seep into the wood. Potential opportunities for cross-contamination will increase.
Can You Use Polyurethane on:
Polyurethane finishes are not food safe when they get exposed to actions that undermine their hardened structure. Remember – polyurethane creates a hardened film that protects the underlying wood surface. You never want to use polyurethane on a surface that is going to get marred, cut, or damaged.
If your cutting board is used only for decorative purposes like a cheese or charcuterie board where no heavy cutting or scratching occurs, a polyurethane finish is acceptable.
A polyurethane finish can be a great choice for butcher blocks. But the idea of “butchering” on a block of wood sounds much the same as a cutting board. If the intended use of your butcher block is to process food with sharp kitchen knives and utensils, don’t use polyurethane. You’ll want to use other food-grade types of finishes.
If your intent is to enjoy the look of your butcher block and you want to retain its finish for as long as possible, a polyurethane finish will do the job. Just be sure to always protect the surface from sharp edges and scratches during food prep.
As with butcher blocks, wood countertops can benefit from a hard, smooth, and shiny polyurethane finish. They just need careful attention.
Natural wood countertops are generally used to give a contrasting or textural look and feel to a room for aesthetics. When used in the kitchen under high-use conditions, a polyurethane coating will stand up relatively well. However, it will inevitably require recoating as dings, scratches, and dulling occur.
Kitchen and dining room tables are a great choice for a polyurethane finish. Given the amount of daily use these pieces of furniture can get, it can benefit from a tough and durable, food-safe finish. It will, however, need protection from moderately hot plates, spilled liquids, and inadvertent scratches.
Bowls/Plates & Utensils
Like cutting boards and butcher blocks, wooden bowls, plates, and utensils shouldn’t be coated with polyurethane. Metal forks, spoons, and knives eventually scratch and loosen the polyurethane finish. The coating on wood utensils can quickly break down from the constant grating of hard tooth enamel against the finished surface.
Is Varathane Polyurethane Food Safe?
Rust-Oleums Varathane Polyurethane is a polyurethane-based sealant that has been around since the 1950s. Its popularity comes from its ability to produce high-quality, durable finishes with extremely fast-drying times. When used to seal wood surfaces it claims its oil-based product is fully cured within only 72 hours.
As can be said for every polyurethane wood finish, they are all food safe – in their cured state. It just so happens that Varathane Polyurethane can reach its food-safe state much quicker than most other brands.
What Is The Best Food Safe Polyurethane?
Deciding on a food-safe wood finish can be a relatively easy task once you decide how your piece will be used and handled. Let’s take a look at two polyurethane finish products that can fit into any type of wood coating project that requires a food-safe finish.
Varathane Ultimate Polyurethane, Oil-BasedThis oil-based wood finish is a great choice when time and funding are limited but food safety, durability, and stain resistance are a priority. It has one of the fastest known drying times and lets you finish your applications in hours vs days.
It’s fully cured in only 72 hours – which alleviates the usual 30-day wait time associated with other oil-based products. Consider using it on any of your wood projects where protection against slightly higher than normal wear and tear is a concern.Varathane Ultimate Polyurethane, Oil-Based is a very reasonably priced product and is considered a great value. It is sold in gloss, satin, and semi-gloss finishes. A quart of this sealant will cover 150 square feet. That’s enough to cover an average kitchen with 30 square feet of countertop with up to 4 coats. The manufacturer recommends a minimum of only 2 coats.
General Finishes High Performance Polyurethane Topcoat, Water BasedThis water-based wood finish is highly valued by woodworkers and furniture restoration professionals. They need a great-looking but extremely hard, scratch-resistant finish. It has a reputation as one of the most durable finish coats on the market. It even has a UV stabilizer to protect any underlying wood stains from fading.
There is a 2-4 hour dry time between coats with a cure time of 21 days. The slightly higher cost and extra cure time become a non-issue after seeing the results.General Finishes High Performance Polyurethane Topcoat is sold in 1-gallon, quart, and pint-sized canisters. A quart will cover 150 square feet. Three coats are the recommended minimum with many professionals adding an extra coat or two for added durability.
Taking on a finishing project in your kitchen or dining room can be confusing, time-consuming, and daunting. Knowing when to use or not use a polyurethane finish coat can make the process go a little smoother. Hopefull, this article helps you to make more informed decisions about using polyurethane finishes for food safety.
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