# WALNUT OIL: a wood bowl finish?



## Mike Jones (Oct 17, 2014)

WALNUT OIL: A wood bowl finish?


It has been a lot of years ago that I had my first experience with walnut oil. Figuratively speaking, that experience left a bad taste in my mouth that lingered for months. To be fair about it, my disappointing results back then came more from my wrongheaded expectations than from problems with the product itself. My project, (a large oak pitcher), continued to bleed oil for weeks after application and even more so when I placed the pitcher in the California sun to help it dry. Later, that same year, I had the opportunity to speak personally with Mike Mahoney, a well-known purveyor of walnut oil, regarding the problem that I had and what I had done to try to “save” my work. It turns out, according to Mahoney, that my solution to the drying problem had actually compounded my problem. By putting another finish over the top of the walnut oil, I had sealed off the oxygen that it needed for curing, and in this way, he told me, the entrapped walnut oil “might never dry”.


As the years passed since that “lesson learned”, I have more appropriately used my walnut oil on wooden spoons, spatulas, and tool handles, and I got from it pretty much what I expected from it But I’ve been continually surprised to read posts in various forums by other woodturners who report favorable results with walnut oil on wooden bowls and even more surprised to read some rather surprising claims about it. Understandably, many of these forum posters believed that the walnut oil that they buy is somehow ‘special’.... that it is not like “ordinary” walnut oil….apparently because they believe in some extraordinary way that it is formulated or processed..


I’ve had an opportunity to do some research this summer and I have found plenty of valid information that is readily available to anyone interested enough to look for it. And, with a few phone calls, and short drives from my home, I have found orchardists, walnut producers, and walnut oil sellers that were quite approachable and pleased to offer their expertise. 


The books and articles written by our trusted wood finishing authors such as Bob Flexner, Michael Dresdner, and Russ Fairfield don’t go much beyond mentioning the existence of walnut oil.....but I find even the omission of such information to be rather revealing! It was interesting too, that in one instance, the Director of Quality Control for a walnut oil producer was not even aware that their product was being used as a wood finish!


I have learned that more than 99% of all walnut oil that is sold in the U.S. today comes from California. There are over 4000 walnut growers registered with the California Walnut Growers Association. These growers will ship and combine their annual crop each fall to one of 80 processing plants (called “handlers”) that are located strategically around the State. Of these 80 handlers, fewer than a handful process the nuts for oil,, and each and every one of those handlers produce their oils under the guidelines, oversight, and restrictions of The California Walnut Commission, the FDA, and other State agencies. The oil produced by these handlers are called “refined” walnut oils and there are remarkably few differences in the way that these corporations refine their oil.


The process of refining includes: cleaning and removing husks and any unwanted orchard debris, drying to around 8% Moisture Content, cracking the shells, fumigating, and sorting the meats then mechanically pressing. The ‘press cake’ and oil is bleached, mixed with solvent (typically hexane), and the batch is then heated to around 400 deg. F to drive off the solvent. Next comes cooling, filtering, and finally, containerizing for shipping. Walnut oil is only made using the least marketable nut meats...the smallest of pieces, darkest colored, most misshapen of the annual crop that would otherwise have negligible value in the marketplace. And it is only made once a year.


The biochemical breakdown of refined walnut oils will vary slightly from region to region, cultivar to cultivar, and crop-year to crop-year, but all will yield test results for the essentials (for fatty acids, linoleic acid, linolenic acid, oleic acid etc.,) within a predictable and narrow range. This predictability, which has been established in testing labs over many years, is essential to the cosmetic, art supplies, and soap industries as well as for culinary reliability. Woodworkers rely entirely on walnut oil’s ability to dry or to “cure”. and while some authors refer to walnut oil as one of the “drying” oils, (along with tung oil and linseed oil), others place it the category of “semi-drying” oils.


I found that there are only two types of walnut oil that are commercially available,: refined (as described above), and Cold Pressed. The Cold Press process for extracting the oil from the nut meats differs from the refined oil process primarily in that, no solvents are used to extract the oil, and thus, no need for the high temperatures necessary to drive off the solvent. 


For the culinary market, cold pressed oils will retain more of the healthful qualities, and preserve more of the subtle flavors of the nut, but typically will be a bit more expensive. For the woodturning community, there will be no discernible difference between the oils produced using either method, and they will both predictably contain the unsaturated fats and oxygen needed to either polymerize... or to spoil Cold pressed walnut oils are typically produced and sold by smaller, independent, “family” type operations that take great pride in the quality and freshness of their product. They will proudly label their product clearly stating that it is Cold Pressed, and typically will have a “Best Used By……..” date printed on it as well. A “Best Used By:......” stamp is an indication of freshness, not safety, and is voluntarily applied. The date shown is usually two years after the harvest year of the oil.


After all, walnut oil is a perishable product and all of it that is shipped out of the processing plant is 100% pure, food grade, walnut oil and it will be degraded over time by dissolved oxygen molecules “attacking” unsaturated fat molecules. This oxidative deterioration is called “rancidification” and it begins the day it is made. For culinary purposes, walnut oil in an unopened original container, kept in a cool and dark environment, would be expected to be useful for two years from the harvest date. If refrigerated, another year, at least.


For the woodturner, determining the useful life of stored walnut oil is just a bit more challenging and complex. It takes a very long time for walnut oil to deteriorate to the point of smelling bad. But, because rancidification and polymerization are competing mechanisms, at some point in time, oxidative deterioration (rancidification) will have progressed to the point that there would not be enough unsaturated fats remaining in the oil to allow complete or timely polymerization. Conversely, if we can get it from the liquid state into it’s solid state, (polymerized) it can no longer rancidify. If walnut oil did not have the chemical potential to become rancid, it also would not have the chemical potential to polymerize. By comparison, mineral oil will test at zero unsaturated fats content, and it will neither dry nor become rancid.


Rancid walnut oil will, however, leave an unpleasant (and lingering) aftertaste in the mouth. Even when it is fresh, refined walnut oil will have a rather bland taste, but certainly, neither the flavor nor the aftertaste of fresh walnut oil would be described as “unpleasant”. Even when it has deteriorated beyond agreeable use in the kitchen, the oil might still polymerize and have some use in the shop. To force a faster cure time, some turners heat enough oil to do the bowls that are ready for finish. Heating more than can be used soon could lead to faster rancidification and a shortened shelf life


Is it a bad practice to use bad tasting, ‘rancid’ oil on salad bowls? That would be a question every woodturner would have to answer for himself. I certainly would not expect any other bowl finish to taste particularly good either, but there is a big difference in my confidence in the complete polymerization of various film finishes over a straight oil finish. Oxidative deterioration begins on it’s “Born On,,,” date and continues through shipping, containerizing, labeling, and in inventory before it is shipped to you. And, we must always remember that the age of our oil is not determined by how long we have had it in our possession. It is safe enough, quick enough and easy enough for turners to determine if their oil is rancid by simply tasting a bit of it. Then, if you wouldn’t use it for salad dressing, would you want to use it on a salad bowl?


My mistake those many years ago was in thinking that a “Walnut Oil Finish” would be something like “Danish” Oil, “Antique” Oil, or one of the “Tung Oil Finishes”, but, of course, my thinking was all wrong. Without a varnish component, straight walnut oil leaves little to nothing at the surface of the bowl to protect the wood from staining, scratching, or water spotting. At it’s freshest and very best, fully cured walnut oil tests out to be only harder than a wax-only finish. Without a resin component, it’s solid form is very elastic and reminds me a of rubber cement or dried silicon sealer. Without a drying component, the straight oil is absorbed into the wood where “the sun don’t shine”, as they say. Because of this, I would be concerned that even a wax top-coat would be just as “oxygen inhibiting” as any other top-coat, (which both Mahoney and Lee Valley cautions against). Consequently, walnut oil encapsulated in the wood and under a top-coat barrier, being deprived of both UV light and oxygen, might never dry and would eventually rancidify.


In the various forums that I visit, it has been said that one advantage of using walnut oil, is that it does not “yellow” as much as does linseed oil, or even tung oil. But when walnut oil is used “straight” and winds up below the surface of the wood, it’s color (or lack of it) is pretty meaningless. It would be an advantage if it were able to be “built up” into a film finish. Another advantage that I’ve heard...that walnut oil finish is easily restored or repaired. Well, if a bowl that I make winds up at someone else’s home, I would hope that restoring or repairing a finish would never be an issue.


There have also been many questions about reaction to nut allergies regarding the use of walnut oil on kitchen ware. The answers that I found indicate that while a very small fraction of the population reacts to walnuts, there is ample reason to believe that, once converted from the liquid to the solid (fully polymerized) state, the finish becomes insoluble... making the potential for allergic reactions next to none.


A more important concern should be that untreated wood, being quite absorbent, will “suck up” just about any liquid that we put on it. When “utility” bowls leave my shop for sale or for gifts, I will never know how they will be used, how they will be cleaned, or maintained. I can’t make a wood bowl bulletproof, but I definitely want the wood to be sealed against any of those common dressings and sauces that could encourage bacteria to grow in the pores and grain in the wood. Bacterial contamination will work up another kind of offensive (and, potentially harmful), odor and taste. (think of a dirty dish rag!) 


I’ve learned that tung oil is very water resistant and linseed oil is not. I don’t know how walnut oil rates in that respect, but my own fail-safe shop test is very simple. I apply a sealer and when it has dried, I apply another coat. If the wood will absorb more sealer, I know it is not yet sealed against liquids, and must be coated again...and then again, if necessary, until no more can be taken into the wood. To properly follow a regimen like this with walnut oil would take months. To fail to do so could leave a bowl vulnerable to absorption of bacteria- breeding food stuff and this would eliminate that whole “food-safe finish” concept.


I am looking forward to stocking up on fresh-from-this-years-harvest walnut oil and it should be ready to pick up by the first of the year. I’ll be using it wherever I might otherwise use olive oil in the kitchen. I have many excellent, time proven, alternative finishes for the bowls that I make, and that won’t leave me with a bad taste in my mouth, either figuratively or literally speaking!.

Reactions: Great Post 4 | Informative 5


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## Kevin (Oct 17, 2014)

I haven't read all this yet but I will. We have been using walnut oil as one of our main oils for several years. We also use high grade coconut, avacado, EVOO, grapeseed, seasme, and flax. Coconut oil is best for cooking high temps and we use EVOO for low temp sauteed foods. The others are for specialty recipes and homemade salad dressings. I also take Carlson's lemon flavored fish oil as a daily supplement. I love the way my burps taste.

Reactions: Thank You! 1


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## Kevin (Oct 19, 2014)

I just read it. Mike, this is one of the most well-written & informative articles I've read in a long time. And with the exception of a few very minor punctuation errors this is _English teacher level_ writing. THAT is a breath of fresh air all by itself and deserves mention. But it gets even better . . . .

You must have taken a notepad when you were speaking with the men & women in the industry and you obviously approached it like Dick Tracy trying to crack a case, but in this case you were cracking a nut. I hope you consider submitting this to the various woodworking mags for publishing. I can't see how they wouldn't want such a well-written, expertly-researched,and frankly groundbreaking article, in their magazine.

Well done Mike. I encourage all of our members to take the time to read this. I will definitely read it again in a week or two. I retain things better when I read them about a week apart. Thanks for putting this up for us here at WB.

Reactions: Agree 1


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## barry richardson (Oct 19, 2014)

Great read Mike! Can other finishes be used over walnut oil once it's cured? Used sort of like BLO to pop the grain?


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## Mike Jones (Oct 19, 2014)

I'd say yes. But I'll suggest that you read this "Instruction Sheet" from Lee Valley....then consider your options.
http://www.leevalley.com/us/shopping/TechInfo.aspx?type=a&p=59385

Reactions: Thank You! 1


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## DKMD (Oct 20, 2014)

Interesting read! I've read it twice now, and I came away with a few questions. If Mahoney recommends against wax coating, I wonder why he and others market oil and wax combos? 

I've read that Mahoney's oil comes from the husks rather than the nut meat. I'm not sure that's true, but if it is, I wonder if the composition is any different than the nut generated version.

As to the allergy question, I've read that the majority of the offensive protein is filtered out of walnut oil. As you said, once dried(if it dries) it should be fairly benign. Given the severity of many nut allergies, I wouldn't want to test the theory!

Utility bowl finishing is a conundrum for me. I like the simplicity of walnut oil, but like you, I question the durability and protection. Film finishes look great, but I worry about repairs when it inevitably breaks down or wears away. I still haven't found a 'perfect' finish for utility bowls...

Reactions: Informative 1


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## Mike Jones (Oct 20, 2014)

DKMD said:


> If Mahoney recommends against wax coating, I wonder why he and others market oil and wax combos?



I can only guess at this. Presumably you would only wax over after you were certain that the oil was dry.
I believe that many turners are not entirely satisfied with the flat, low sheen appearance of the oil only finish, so, the answer is to sell them a wax that will buff up a shine.



DKMD said:


> I've read that Mahoney's oil comes from the husks rather than the nut meat. I'm not sure that's true, but if it is, I wonder if the composition is any different than the nut generated version.



One of the reasons that I went to the trouble to write this was to dispel such notions. They make dye out of black walnut husks, and some abrasives out of the shells....but there is no oil in the husks.



DKMD said:


> As to the allergy question, I've read that the majority of the offensive protein is filtered out of walnut oil. As you said, once dried(if it dries) it should be fairly benign. Given the severity of many nut allergies, I wouldn't want to test the theory!



Cold Pressed Walnut oil is pretty much just squeezed oil and retains the proteins. Refined walnut oil, as is Mahoney's, will lose some of the proteins. The people that do cold pressed stress the difference...the people that make refined, downplay the difference.



DKMD said:


> Utility bowl finishing is a conundrum for me. I like the simplicity of walnut oil, but like you, I question the durability and protection. Film finishes look great, but I worry about repairs when it inevitably breaks down or wears away. I still haven't found a 'perfect' finish for utility bowls...

Reactions: Thank You! 1 | Informative 1


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## Kevin (Oct 20, 2014)

Mike I added the quote tags to make it easier for members to tell who said what.  

This is a great thread guys. Excellent questions Keller.

Reactions: Thank You! 1


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## Mike Jones (Oct 21, 2014)

I really do appreciate the questions because it tells me where I need to make my points clearer. I also want to say that we are not "bashers" here on this forum, and I did not want to pick on any particular supplier....not wanting to accuse anyone of deception regarding their product(s).



DKMD said:


> Utility bowl finishing is a conundrum for me. I like the simplicity of walnut oil, but like you, I question the durability and protection. Film finishes look great, but I worry about repairs when it inevitably breaks down or wears away. I still haven't found a 'perfect' finish for utility bowls...



Some of the wipe-on varnishes are tough enough to be used on exterior boat decks and some durable enough to be hardwood floor finishes.

Reactions: Like 2 | Useful 1


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## Mike Jones (Oct 22, 2014)

DKMD said:


> Interesting read! I've read it twice now, and I came away with a few questions. If Mahoney recommends against wax coating, I wonder why he and others market oil and wax combos?



First, I would clarify that Mahoney advised against overcoating bowls and large surface forms such as my oak pitcher with a faster drying film finish. It was my own inclusion of wax as having the same sealing out of oxygen as would the film finish.
It also occurs to me that these wax emulsion products are made for finishing spindles, tops, boxes, ornaments, and any other mall turned forms. But he does not provide instructions for it's most proper use.

Reactions: Like 1


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## HomeBody (Oct 22, 2014)

Good info. I'd never even heard of walnut oil until now. Gary


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## duncsuss (Oct 22, 2014)

Mike -- I've read your article a couple of times now, and will probably have to read it a few more times before it finally sinks in to the point I can ask a sensible question. Thank you for your time researching the subject, and for writing it up to share with us.


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## Vern Tator (Nov 14, 2014)

An interesting article. I use it almost exclusively for my bowls. I sent a link to my friend Mike Meredith, who makes some finishes that he markets as Doctor's Woodshop, to see what he has to add to the conversation. By the way, I really like all of the finishes that he makes.


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## Mike Jones (Nov 14, 2014)

Vern, Mike Meredith was one of my sources for information. I will be pleased (even excited) to hear what he has to say!


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## elnino (Nov 20, 2014)

yeah i also think that mahoneys utility oil might be heated in the absence of oxygen to a point that the oil start to polymerize but need oxygen to truly harden.

of course i could be total wrong about this. maybe i'll have an organic chemist check the utility vs cold pressed walnut.

I do like the idea of the Mike Meredith finish too. ask him if his oil is heated.


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