Natural, Food Grade Stains & oils for Cutting Board

[JayCee71]

Hello all, first post here, and I'm new to woodworking. As it seems with many newbies, I plan on making a few end-grain cutting boards/butcher's blocks to gain some experience with the machinery at my local workshop. I just found a lot of nice thick hardwood that's quite pale (council cleanup), and I am wondering about applying some natural stains to give each section of the board some different colourings.

Been looking at coffee, tea, (and I'll even try spices such as paprika, tumeric) mixed with vinegar, but I'm wondering how deep these soak in, because I'll be doing a lost of sanding back, post construction. There's no point if it only soaks in a couple of millimetres. Can i soak pieces of timber in a colouring solution or is that going to render the wood useless for weeks/months until it dries out?

Also, it seems a hot topic around the internet as to which oils are best for food applications, he verdict seems to be either mineral oil or raw (not 'boiled' linseed oil. The linseed however appears to have a very long curing time, so I'll just as soon go for mineral oil. The question is, where are some stockists in Australia... brand names ?

I have determined that the best glue for the job is Titebond III, being both food grade and waterproof... and fortunately the new big blue shed stocks this product.

[Robson Valley]

I carve Kitchen Sticks which get an oven-baked olive oil finish that takes advantage of Charles' Law in physics.
I refuse to use mineral oil or linseed oil of any sort = I have yet to see either of those in any cookbook for any reason.

[NathanaelBC]

I've never oiled a raw board, but I maintain all my chopping boards with linseed oil and it works for me. Dries quickly, no issues with rancidity. Got the oil from a health food shop, kept in a fridge and just warm it up before applying.

The oil that IKEA sells for board care is mineral.

[Robson Valley]

Can you explain the "issue with rancidity", please? There is not enough air
inside the heated/cooled wood for oxidation. But, if your kitchen never gets used. . . . . .
I expect that my Kitchen Tools are working tools, not decorations.
If they were meant to be decorations, I would have used some funky laxative (what fun!)
like mineral oil. Come to think of it, I just might make a special tool run for some people
that I wish I didn't know.

When was the last salad dressing recipe created with mineral oil? Yuk.

[robbygard]

I carve Kitchen Sticks which get an oven-baked olive oil finish that takes advantage of Charles' Law in physics.
I refuse to use mineral oil or linseed oil of any sort = I have yet to see either of those in any cookbook for any reason.

i thought charle's law was that:

watt's pots never boyle



regards david

[JayCee71]

There's seems to be a lot of debate about oils, and in theory I can understand your position, Robson. However mineral oil (and raw linseed) is FDA approved in the USA, so that would account for some level of safety, one would assume. Bearing in mind that plain old white vinegar is rarely questioned as a 'food stuff', but is alleged to be a byproduct of petrochemical production, then the 'food safe' accreditation may well be in the level of processing.

I'm no expert on wood treatment, but will throw out a theoretical scenario on using olive oil. A bit of background first: I have a fair knowledge of the 'concept' of oxidization, as I was an all-grain beer brewer for a number of years - however it's another hobby of mine that I wish to draw comparisons against, and that is Mycology, or the study of fungi. Making a broad stroke here to say that some bacterias and some fungi thrive in similar environmental conditions, one element that promotes vigorous rhizomorphic growth in fungi genus is oxygen, nitrogen and carbon dioxide (ie; air) and free gas exchange (of co2).

Now, if we observe the commercial growing process of Shiitake mushrooms in Japan (the world's biggest producer of this fruit), it's done by colonizing hardwood logs, and is widely accepted as the premier method amongst mycologists the world over. Through this growth medium, the mushroom mycelium is thriving under the long grain surface, and is receiving enough air & gas exchange to promote growth. Therefore it might stand to reason that the more porous end-grain of a wood will exhibit a greater level of air & gas exchange, therefore promoting further growth of mycelium, and by circumstance of similarity, select bacterium.

I'm sure we all agree that olive oil does 'go rancid' under less than ideal storage conditions, so with the consideration of it's application on an end-grain chopping block, the degradation of olive oil to a rancified state may be more prevalent than you think. Whether this would actually pose any health issues remains to be seen, because humans live in a world whether we breathe and ingest all manner of bacteria each second. Select mould strains (a biological similar to fungi) are even promoted in gourmet foods, such as cheeses & sourdough bread starters. Traditionally made 'mother-born' vinegars promote the growth of bacterium.

My question would be, in the olive oil vs mineral oil discussion, does mineral oil also 'go rancid' when placed under the same conditions as olive oil? I would like to say that I can do some tests over the next few months on a pseudo-scientific level by growing out the nasties on an agar petri dish, but I'm reluctant to introduce unwanted coliforms into my already filthy household/occasional bio-lab.

PS: Robson, what are kitchen sticks - I'm assuming it's a term for homemade striing spoons, spatulas, forks etc?

And a quick thanks to Nathaniel and the IKEA link. I'm just up the road from an IKEA. Although it's $10 there, and I just found a 'U-Beaut' food safe mineral oil product for $12... they are one of this website's site sponsors, right? I would just as soon spend a couple of dollars more, because I'll undoubtedly be picking up a whole lot of tips from the community here. More than I would by reading flat-pack assembly instructions !

[Robson Valley]

Kitchen Sticks are prep tools as you surmise. There's a thread of that name in the Wood Carving Forum.

"Food Grade" mineral oil is likely fully hydrogenated (so little chance of spontaneous oxidation) and the chains are short enough that the material remains liquid at room temperature. Either that or the oxidation products are tasteless.
The fatty acids of the plant triglycerides have at least one double bond in each chain which can be oxidized. One extreme is arachidonic acid, the fatty acid in peanut oil, with 4 double bonds per chain. Olive oil fatty acids (linoleic?) have just 1 each in the three.

It's my experience with fairly intensive use of my KS in my kitchen over the past 12+ months that the baked-in finish
is not displaced by food liquids, hot or cold. In fact, to move what residual air might be still in the surface wood of the stick, it must be reheated to 350F.

At the end of the day, I'll do what works in public sales.

Watt's pots don't Boyle? Oh, please! Fortnight joke = 2 week/weak. ( I love it!)

[JayCee71]

So an oil devoid of triglycerides is going to remove any possible chance of bacterial contamination transfer to the food being prepared. A non-plant derived oil seem the safer bet. Mineral oil goes a long way towards removing any bacterial risk. As for human contamination, it seems to be used widely in many health & beauty products, and there aren't any overwhelming reports of transdermal administration of the oil entering the blood stream with adverse effects. After much thought, I'm going to go with this option.


Any comments on using natural products for staining?

[Robson Valley]

If the mineral oil had branched hydrocarbon chains, so much the better. Enzymes that can handle branch points are few and far between. Do as you please. I pointed out that mineral oil never appears in any recipe, salad dressing or otherwise, that I've ever seen.
I have a bottle of it, intended to use it as a wood finish. The label says it's a laxative. I will use it as a special treat for particular people who, I'm certain, need it badly.

Somehow, revealing that the Kitchen Sticks had an oven-baked, laxative, mineral oil finish might not have been an appealing sales point.

There are all sorts of natural/biological sources of dyestuffs. Lichens with ammonia have been used for many centuries to dye wool. Fantastic reds and oranges if you can find the right ones. The problem, eventually, is that they are not light-fast and tend to fade to gray over time. Partly oxidation, partly UV damage. Coffee, onion skins, grape solids (anthocyanins), cochineal. The "Royal Purple" that the Romans were fond of was a mollusc derivative if my memory is still working.

[rob streeper]

Have a look at this re: Bacterial contamination of wooden cutting boards. http://faculty.vetmed.ucdavis.edu/fa...ttingboard.htm
Wood is pretty inhospitable for many pathogenic bacteria.

As to linseed oil be careful. The stuff for wood working often contains accelerants to hasten the hardening of the oil and these can be toxic if consumed. Raw food grade linseed oil is flax oil - darling of the health food crowd - and it will also oxidize as does woodworking grade boiled linseed oil, it just takes longer.

Another finish you can try is Behlens Salad Bowl finish, American Finishes has a similar product and both are FDA approved for food contact. I've used the American Finishes version and it works quite well but you need to apply three coats or so to get good coverage.

Cheers,
Rob

[surfdabbler]

I have used Mineral Oil on my serving tray. It can be bought from the chemist for far less than the cost from the hardware shop. I think I bought a 300mL bottle for about $3. It makes a nice looking finish on the board, and stops other food oils from getting in, however, I've noticed that it does wash off fairly easily under hot water and detergent. I don't think mineral oil hardens at all in the wood. So, cleanup of the cutting board is limited to paper towels and cold water, and regular re-applications of the oil. Also note that mine is a rosewood cutting board, which was probably not the best wood to use - too lightweight, and probably too open grained to hold the oil properly.

As for the laxative properties of mineral oil, yes it is a mild laxative (that's why it is sold at the chemist), but with a recommended daily dose of 1 teaspoon, no-one's getting that much oil out of the board. The minute amounts that may occasionally be consumed from coming off the board are not enough to have any effect of that sort.

For the natural stains, I would expect them not to go far into the wood. You could do some tests, but I wouldn't expect that you could sand it much at all before losing the stain.

[rob streeper]

All

I've looked further into the BLO question and have come across a number of interesting bits of information. First there is a nice explanation of the chemistry of drying oils, BLO, walnut oil, tung oil etc. https://openaccess.leidenuniv.nl/bit...pdf?sequence=2.
In summary, oils that are polyunsaturated (contain several double bonds) will react with oxygen from the air to form polymeric oxides. These polymers are not soluble in the vehicle used to apply them.

This polymerization is accelerated by the addition of various metal catalysts including oil soluble compounds of lead, iron, zinc, titanium, calcium, zirconium, cobalt and probably some proprietary mixtures of these and other metals. These metals are responsible toxicity concerns associated with commonly used woodworking products. These agents are also known as Japan drier. Finding information on the exact composition of Japan driers is difficult - the manufacturers are trying to keep these as trade secrets - the MSDS's refer to 'metal carboxylates' without naming the metals. Not exactly helpful to an emergency-room doctor needing information quickly to treat someone.

It is possible to use raw oils of this type such as food grade raw linseed oil that is sold as flax oil. For a cutting board, especially if in a light colored wood, you could also use soybean oil as it is a drying oil too. I've never used it but it is cheap and readily available.

[JayCee71]

For the natural stains, I would expect them not to go far into the wood. You could do some tests, but I wouldn't expect that you could sand it much at all before losing the stain.

I don't know about that. If you consider that the end grain edge would be stained, then I think it would suck a vinegar or water solution right in. Looking at some videos of guys oiling their end grain boards, it soaks through to the other side. I'm going to do a few tests tomorrow, leave them a week then glue them up. My concern is that the stain may transfer to the unstained slats, but we shall see. I'm a big fan of experimentation over theorizing so it will be a pleasure to either confirm or deny the efficacy of food stains for my purpose.

[Robson Valley]

I think that you will find that the oils can and will interfere with the glue-up, if/when they come into contact.
I suggest that the oil finish be the last step before service.

I don't think there will be much lateral stain transfer from one stick to the next, in an end-grain application.
Transport in wood is mostly vertical and the stains/oils are far larger molecules that water. As well, the surfaces of the sticks will be coated with glue and that should do a fair job of sealing one stick from the next.

I looked up "food-grade" mineral oil, seems to be a distillation byproduct from crude oil, alkanes in the C15 - C45 range. I cook with olive oil, I'll keep with that.