Food Safe Wood Treatment

May 7, 2008 12:33 PM

I'm planning to use bamboo plywood for a section of kitchen countertop. How should I treat it to make it both water and stain resistant and food-safe?

I like the look of this, - its a fairly subtle poly, not the thick built up layers kind.

But would it be safe to use on a surface that might have occasional contact with food? I'm not planning to use it as a cutting surface, just a surface for cutting boards, plates etc.

posted by RandlePatrickMcMurphy to home & garden (8 comments total)

Well, if it will only have occasional contact with food (not as a prep surface) you can use pretty much any finish that you would on a kitchen table - which is to say everything. Wipe on poly should be fine. Traditional wood prep finishes are pentrating oils or wax, but I'm not sure how well they would work with plywood. I'd also recommend you search for "salad bowl finish" - it is a curing finish that can be used for food contact surfaces. Don't use shellac, although it is a wonderful finish it does not handle water or alcohol spills well.
posted by true at 1:45 PM on May 7, 2008

If you're concerned about food contact, you could oil it with a vegetable, rather than mineral oil. That will give you stain and water resistance. Nothing will make it stain/water-PROOF, of course, other than hard poly lacquers on top, of the sort you'd use on hardwood floors. Rather cold.

I had a large, olive-oil rubbed cutting board for many years. I loved it, and used it for almost everything... and have often considered making an entire counter or cart-top the same way since. Some day.
posted by rokusan at 2:13 PM on May 7, 2008

I wouldn't recommend salad bowl oil or vegetable oil for a countertop. That's the way to go for a cutting board or wooden bowl, but you'll likely want more protection for a countertop. Polyurethane will set up hard and protect the material underneath. As long as you fix up any areas that start to chip, you shouldn't have any food safety issues - the worry is consuming flakes, not occasional contact.

If you really like the natural look, you could probably do the salad bowl oil treatment, but you'd need to sand off the scratches and scuffs every couple of years. That wouldn't work too well with plywood - once you start going through the top layer, it'll look patchy and nasty.
posted by echo target at 3:23 PM on May 7, 2008

the harmful parts of the poly are volatile annd evaporate fairly quickly. that said, the water based poly is healthier and also should deal with water sitting on it better.

that said, your plywood counter wiill not lasst so long... it's kind of a bad idea. eventually water is going to get into the counter and it will delaminate.

if you are set on doing this, make sure to sand it really smooth and do at least three coats of poly until it has a good membrane protecting the plywood from it's enemy: water.
posted by geos at 4:06 PM on May 7, 2008

i recently filled a gap in my counter with a large bamboo cutting board. I had some plants on it, and after a few weeks, one of the plants with a clay pot was almost glued to the bamboo. When I pulled it off, there was some funky black mould growing on the bamboo. I'd heard that bamboo was naturally mould resistant, but there is at least one mould that likes to eat bamboo out there.

I suggest treating it with something that can seal out water completely. Olive oil is a nice idea, but I don't think it will be durable enough.
posted by kamelhoecker at 6:00 PM on May 7, 2008

I wouldn't recommend salad bowl oil or vegetable oil for a countertop.

Vegetable oils will go rancid when exposed to light and air. The recommendations I've heard have been tung oil or mineral oil, plus beeswax. All of them have to be renewed frequently- like every month, up to every week. I also have to wonder about the suitability of plywood in an area that has moisture.
posted by oneirodynia at 6:40 PM on May 7, 2008

Food grade Mineral oil is the safest for a non drying food safe finish. A bottle large enough for a life time supply is only a couple of dollars at your pharmacy (it's a laxative). Modern hardwood plywoods have a paper thin veneer layer and make poor wear surfaces; however, at least one source of plyboo has veneer surfaces a millimetre or two thick sandwiching a block core. Something like that in say maple, would work pretty good with a non drying finish but I've never used bamboo. However they make salad bowls, spatulas and other food prep tools out of bare bamboo so it shouldn't be completely horrible. Too bad it appears to be ~$150 for a 3/4" sheet.

The problem with a thin wipe on poly (or any poly for that matter) is they aren't repair friendly and they are are brittle to boot. A chip, scorch or scratch essentially requires sanding a large area to below the damage, often to bare wood, and then refinishing. It's pretty easily damaged with a slipped fork, or a shattered piece of glassware.

Envirotex is designed for this purpose. It is heat and impact resistant, impervious to both alcohol or water and is resistant to a lot of the acids in foods. Normally it produces a high gloss glassy finish. You can however get a satin finish from envirotex with a little work:

"Use Pumice or Rottenstone polishing powder and a wet sponge. Lightly wet the Envirotex Lite surface, then sprinkle with polishing powder. Apply a firm, slightly wet sponge and move in small circles until the entire surface gloss has been removed. Wipe surface clean and polish with paste type polish."

I've seen this done using 0000 steel wool instead of the pumice. A 100% carnauba wax softened with mineral oil (cheap) or beeswax (expensive) is a food safe option for the last step and will result in a durable surface that is easily renewed.
posted by Mitheral at 8:19 PM on May 7, 2008

Thanks for good suggestions.

Just to clarify on the material - I'm using a plyboo as mitheral suggests, but its the edge grain, which doesn't have a top veneer that would be sanded away. (And its more expensive than regular ply, but still a lot cheaper and easier to work with than more commonly used surfaces; except for stainless steel around the sink, I'm doing the countertops and many of the vertical surface with two 4x8s.)

Follow-up question if anyone is still paying attention: Any experience with tung oil?
posted by RandlePatrickMcMurphy at 6:56 AM on May 8, 2008