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I have a wooden bread bin, with the bottom (floor) bit being a 3.6mm plywood. The rest of the build is solid wood, 12mm thickness. The bin was dropped at one point and the bottom of it cracked; the moisture got in and mould started growing on it.

I decided to replace the bottom altogether and got the same thickness plywood - to make sure it fits into the slots on the sides, front and back. However the question is how to finish it - to make sure it's both water proof and food safe, after all, bread would be resting on it most of the time.

I did consider options such as linseed oil or even olive oil, but those may not be durable enough and (at least in olive oil case) have some odour, which wouldn't be great in a small enclosed bread bin. Ideally, I'd like a film-like finish for protection, but a normal wood stain isn't food safe.

So, what's the best finish for the bottom of the bread bin?

P.S. I'm in the UK if it matters.

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    Most finishes do not have the food safe label on them, mainly because it costs a lot of money. Unless you are mixing/cutting/cooking food on the finish, most should be safe enough to lay food on. A finish that dries hard should not harm food like bread.
    – crip659
    Sep 23, 2022 at 21:04
  • Is the bread wrapped or will it be laying directly against the bottom with no plastic/paper under it? Sep 23, 2022 at 21:14
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    Allow me to introduce you to Woodworking. It's your friend for questions like this. ProTip™: all finishes are food safe once they've completely dried/cured/set. They're done releasing anything that might possibly be toxic at that point and they're 100% fine. Olive oil, on the other hand, will go rancid after sitting out for a relatively short period of time, will stink, and will leave a nasty taste on the bread, as well as possibly make you sick. You can try this out if you'd like, just leave a bowl of olive oil sitting on the counter until it stinks, dip your bread in it and enjoy!
    – FreeMan
    Oct 24, 2022 at 0:04

5 Answers 5

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Summary of non-toxic finishing products for wooden bowls and wood cutting boards:

Mineral oil: derived from petroleum, it is colorless, odorless, tasteless and entirely inert. Simple to apply, low water resistance, frequent reapplication. Highly processed variants are food safe and labelled as such. Do not confuse with mineral oils used as machine oil.

Beeswax: The work of the honey bee, extracted from frames in a bee hive. Best applied when heated. Ask your local beekeeper.

Shellac. A secretion from the lac bug. A film-forming finish, which is easy to wipe and clean with a moist cloth. Use high-purity denatured alcohol as a solvent, as it leaves no toxic residue.

Raw linseed oil: Pressed from flax seeds. Very long curing time, good looks, low water-resistance, frequent reapplication. FOr shorter drying time use polymerized linseed oil which is still food safe, but not "boiled" linseed oil. Rags may self-combust.

Pure tung oil:, from the nut of the china wood tree. Difficult to apply, requires many coats, good water-resistance.

Walnut oil: Pressed from the nuts of the walnut tree. Dries and won't go rancid. Easy to apply, frequent reapplication.

Carnauba wax: Derived from the Brazilian palm tree. Straight on woodenware as a light protective coating or a topcoat polish.

The above is abridged, reordered to my preference, and mildly edited, from https://www.newhampshirebowlandboard.com/blogs/blog/13612445-food-safe-finishes-for-wooden-bowls-and-wood-cutting-boards

More on the variants of linseed oils:

  • Raw Linseed Oil is the purest, most natural form of the oil. It is the kind used in nutritional supplements
  • Polymerized Linseed Oil is created by heating raw linseed oil in the absence of oxygen to about 300°C (572°F) over the course of several days.
  • Boiled Linseed Oil has drying agents (either petroleum-based or heavy metals) added. It is the least food-safe of the three.

Ref: https://vermontwoodsstudios.com/blog/raw-vs-boiled-vs-polymerized-linseed-oil/

More on tung vs linseed oil: https://woodworkingtoolkit.com/tung-oil-vs-linseed-oil/

Self-Combustion of Oily Rags

The reader should be cautioned about the storage of oily rags:

The entire combustion process of the samples includes 4 typical stages: low-temperature oxidation stage, thermal decomposition stage, combustion stage, and after-combustion stage. The activation energy of the low-temperature oxidation stage reached as low as 33.13 kJ/mol, indicating that the vegetable oil is extremely prone to self-oxidation even when the temperature <200 °C. And the self-ignition tendency was in the order linseed oil > perilla seed oil > safflower seed oil The continuous oxidation and self-heating of vegetable oils in the air can result in the occurrence of fire due to thermal runaway via heat accumulation. This is especially true when the unsaturated vegetable oil is immersed in a carrier such as cotton cloth or fiber, as the much larger contact area between O2 and oil results in an oxidation rate and thereby increases the risk of fire. If there is sufficient accumulation in the carrier, the heat released by the reaction can easily accumulate due to the overlay effect of the accumulation. Once the ignition temperature is reached, the oil will burn in the presence of O2.

https://www.sciencedirect.com/science/article/abs/pii/S0360544221031364

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  • Lineseed oil soaked rags are prone to catching fire. I don't know if that applies to raw lineseed oil, but perhaps the user should be advised to take care with oil soaked rags.
    – Martin
    Feb 9, 2023 at 13:22
  • @Martin very good, I added that info
    – P2000
    Feb 9, 2023 at 14:58
  • I went with tung oil - good finish, although took quite some time for it to fully dry and stop producing a smell that didn't got well with bread.
    – Aleks G
    Feb 9, 2023 at 16:22
  • @AleksG thanks for coming back to this old question and providing your feedback.
    – P2000
    Feb 9, 2023 at 16:24
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Clear shellac or mineral oil are your best choices.

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  • Care to expand on that to say why? That would make this useful as opposed to an all-knowing "do as I say"...
    – FreeMan
    Feb 8, 2023 at 19:21
  • Okay sorry. I’ve been a professional woodworker for over 40 years. I’m not a chemist to explain why.
    – Mlew
    Feb 8, 2023 at 19:22
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    Then its worthwhile to mention that in your answer and perhaps find a reference to support it. Feb 8, 2023 at 19:35
  • Simple flat statements without any supporting information tend not to go over well here. Supporting info of "I've been a woodworker for 40 years and have used x for most of those years" adds a fair bit of credence to what you say. Just saying "use x" without explanation doesn't carry much weight.
    – FreeMan
    Feb 13, 2023 at 15:34
  • Who benefits when you say who is right or wrong? I don’t see the other answers critiqued.
    – Mlew
    Feb 19, 2023 at 23:54
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I use mineral oil on anything that needs to be food safe; there are also some commercial oils/waxes that can be used (butcher block oil is the most common I can think of).

Alternatively, you could get a baking/sheet pan that fits inside to rest the bread on/in. This has the added benefit of removing it to clean and empty crumbs that might have broken off the bread.

Also, keep in mind that the bread is far more moist than the air and mold is more a factor of the cracked base allowing mold spores easier access and not a factor of the wood being air permeable.

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Bread bins are not meant to be used in moist environment. Bare wood is perfectly fine in this use scenario. If your bread box experienced conditions enabling mould to grow then the bread inside would also grow it.

Mouldproofing the box alone won't do you any good. You need to dry up the environment.

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Whatever you do, don't use olive oil. It'll go bad and smell nasty.

We could spend months talking about various wood finishes, but for something like this you should just keep it simple.

Water-based polyurethane is the quickest and easiest way to finish wood. It's available at any hardware store (at least here in the US). It dries quickly; leaves a smooth, durable, water-resistant surface that's easy to clean; and unlike many other finishes, it doesn't give off nasty fumes while it's drying.

Put on the first coat, let it dry. You'll probably notice that the surface became rougher than it was before; don't worry, that's normal. Sand it lightly with fine paper (220 or so), wipe off the dust. Put on a second coat. Done. (You can do a third or fourth coat if it's a high-wear surface like a tabletop, but this won't be necessary here.)

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