Shiny finishes with Tung oil?

[John K Jordan]

Tru-Oil, mktd for gun stocks. Gloss only I believe.

Tru-Oil is gloss, however the gun stocks I've used it on were never glossy. Apply the Tru-Oil, then use a padding/rubbing technique with powdered abrasive - first pumice then rottenstone. Last one was walnut came out great. The pumice is coarser and can fill in the pores and flatten smooth/flatten the surface. Repeat with rottenstone to the level of satin sheen desired (prob about a 2000 grit). These both come as powder and are used with some liquid lubrication such as water or some type of non-polymerizing oil. The methods used for gun stocks work well on woodturnings and can be used on a variety of finishes. A little goes a LONG way. I bought cans of both grits 10 years ago and they are still mostly full.

In my experience, the Tru-Oil finish is quite tough, practically impervious to damage by the elements. Could probably scratch it by fighting off a bear with the butt of the stock but I haven't experimented with that.

My earlier warning about Tru-Oil is unchanged - in my experience once opened, it can quickly set up in the bottle unless the air is displaced with an inert gas. I use argon.

JKJ

 

[Jon Rista]

@Jon Rista a thought just occurred to me (can be dangerous, I know). I mentioned TruOil earlier, and then their is the aspect that you need to do this egg finish off the lathe. I think the type of finish you are after is about = to high end gun stock finishes. I know some about how they are achieved, but I think some research into it could possibly provide some good information. This would be a good one to use an AI bot to filter through the gargantuan amount of info about gunstock finishes.

Thanks for the insight, Doug. I'll check it out...I'm curious, is finishing gunstock, similar in any way to french polishing or other heavily rubbed-in finishing processes?

Here are some shots of the eggs I felt needed a glossy finish to really bring out the chatoyance. Two I shared not too long ago, for a wood id (consensus was some variety of plum, probably well-aged plum wood.) The other, is this unknown cutoff I bought for about a buck at Rockler from their cutoff bin. It has some wonderful figure with a lot of chatoyance, but it doesn't shimmer much unless its glossy. Hence...where I'm at. Hopefully one of you will be able to identify the wood. It is porous, however, I am continuing to sand it...I've been wet sanding with the tung oil. I finished through 800 grit, and I have 1000/1200, 1500, 2000 and 3000 grits as well. It IS getting smoother, and more and more visible (but fine) scratches are being eliminated with each grit. I am hoping by 2000 all visible scratching is totally gone. The wood IS porous, you can see that in the remaining chunk of the wood that is left over after turning the egg. The egg, however, the pores seem to be getting filled in fairly well with the oil-wet sanding.





Close ups of the unknown wood egg and offcut:

 

[Jon Rista]

 

[John K Jordan]

Identifying mystery wood:
Read this article on the Wood Database.

Wood Identification Guide | The Wood Database

www.wood-database.com

Follow the instructions in section "7. LOOK AT THE ENDGRAIN." It's fun and useful to learn how to do this.
Or you can get professional help. See the "STILL STUMPED?" section at the bottom (before the comments)

JKJ

 

[Jonathan Silwones]

Jon, I use thinned poly wet sanded at 320 and then wiped off, then 400 several days later. Wait at least a week or two, then buff for a beautiful glow. I have to go to 600 on black walnut (it show fine scratches more than most woods). The thinning of the poly keeps it from getting tacky while sanding. I don't drench the wood with finish because that will greatly extend the curing time. So much advice, so little time.
Good luck!

 

[Jon Rista]

Jon, I use thinned poly wet sanded at 320 and then wiped off, then 400 several days later. Wait at least a week or two, then buff for a beautiful glow. I have to go to 600 on black walnut (it show fine scratches more than most woods). The thinning of the poly keeps it from getting tacky while sanding. I don't drench the wood with finish because that will greatly extend the curing time. So much advice, so little time.
Good luck!

I might need to go to 600, as this wood is a bit porous like walnut. Do you use just a single coat, and still get a glossy finish?

 

[Jonathan Silwones]

I might need to go to 600, as this wood is a bit porous like walnut. Do you use just a single coat, and still get a glossy finish?

any sanding is done wet and then wiped off. all produce a nice gloss. Sanding at finer grits helps on harder woods that show fine scratches. Red oak does great with only one wet sanded coat.
Note: I dry sand to 220 on the lathe.
Hope that helps.

 

[Lou Currier]

I use Tallahassee pure tung oil and dilute 50% with paint thinner or mineral spirits (DNA doesn't play well with tung oil as it separates). Like the OP, I will use multiple coats allowing the first few coats to soak in. I can usually do several coats in a few hours and then let it dry for 24 before reapplying. The oil will cure within 72 hours where BLO usually cures quicker. After the 72 hours I can then apply more coats to the desired look and then buff it after the final drying period. It gives a satin sheen finish look. It is also good as a base before using other finish types and because of the way it penetrates deep into the wood, you don't waste finish that would normally soak into the wood before you can get a good buildup finished look.

 

[Jonathan Silwones]

Lou, I’ve been experimenting with Tallahassee pure tung oil. I was wondering how durable it is for food bowls. I’d appreciate your thoughts.

 

[John K Jordan]

Pure, 100% tung oil is widely considered food safe.

Might be useful to read this:

Tung Oil Myths Debunked: Food Safety, Drying Time, and More

The Truth About Tung Oil: Myths and FactsTung oil is a centuries-old, natural wood finish derived from pressing the seeds of the tung tree. Renowned for its impressive water-resistant properties, rich golden color, and ability to pop-the-grain, pure tung oil remains a top choice for professional...

www.tallahasseetungoil.com

JKJ

 

[Steve Tiedman]

Lou, I’ve been experimenting with Tallahassee pure tung oil. I was wondering how durable it is for food bowls. I’d appreciate your thoughts.

I'm not Lou, but the first few coats of tung/linseed/walnut oil penetrate the wood and polymerize in the wood fibers. Once polymerized, it is essentially a cured, natural "plastic". Food contact and washing will not pull the cured oil out of the wood fibers. The surface will take on a bit of wear and patina, but should look great as time goes by. You're in good shape with cured pure tung oil, just give it a good month, maybe more, to fully cure/polymerize before food and washing.

 

[Jonathan Silwones]

Thanks for the responses folks. My question was about the durability. If you have used it on food bowls and then used the bowls for any length of time, how has it held up?

 

[Jon Rista]

any sanding is done wet and then wiped off. all produce a nice gloss. Sanding at finer grits helps on harder woods that show fine scratches. Red oak does great with only one wet sanded coat.
Note: I dry sand to 220 on the lathe.
Hope that helps.

Thanks Jonathan. This is the approach I'm taking here. The first egg is pretty hard wood (I've tried to identify it but have not conclusively found anything that seems to be a good fit). I can see scratch marks in certain places from the original grits (I think I started at 220, as the initial turning was pretty smooth, but on this wood even that left scratch marks in certain places that I can still see.)

Is there any need to leave any degree of slight roughness for the finish to hold onto, or can I sand as smooth as possible for maximum shine? I'd sand up to 2000 grit here, if I can, to make sure this is as shiny as possible. I'll be using the minwax gloss poly on it.

 

[Jon Rista]

I use Tallahassee pure tung oil and dilute 50% with paint thinner or mineral spirits (DNA doesn't play well with tung oil as it separates). Like the OP, I will use multiple coats allowing the first few coats to soak in. I can usually do several coats in a few hours and then let it dry for 24 before reapplying. The oil will cure within 72 hours where BLO usually cures quicker. After the 72 hours I can then apply more coats to the desired look and then buff it after the final drying period. It gives a satin sheen finish look. It is also good as a base before using other finish types and because of the way it penetrates deep into the wood, you don't waste finish that would normally soak into the wood before you can get a good buildup finished look.

Thanks for the not about DNA vs. mineral spirits.

Sounds like buffing is really what brings out the shine. I have the beall three wheel system. What buffing compounds do you use? Trip and WD, or something else?

 

[Jon Rista]

Pure, 100% tung oil is widely considered food safe.

Might be useful to read this:

Tung Oil Myths Debunked: Food Safety, Drying Time, and More

The Truth About Tung Oil: Myths and FactsTung oil is a centuries-old, natural wood finish derived from pressing the seeds of the tung tree. Renowned for its impressive water-resistant properties, rich golden color, and ability to pop-the-grain, pure tung oil remains a top choice for professional...

www.tallahasseetungoil.com

JKJ

I've been making some food contact products lately. Was going to finish with food safe mineral oils, but, I am a fan of tung oil. I don't think pure unthinned tung oil will penetrate well, though.... Anyone know if there are food safe mineral spirits it could be thinned with for deeper penetration?

 

[Vincent Vogel]

Thanks for the responses folks. My question was about the durability. If you have used it on food bowls and then used the bowls for any length of time, how has it held up?

A neighbor of mine has had a bowl I made her with tung oil on it for two years. I asked her the other day how it's holding up since she actually uses it for its intended purpose. She puts salad in it and dresses the salad before serving it from this bowl to smaller individually sized bowls to eat from. Then she washes it with soap and water and dries it immediately. She said it looks as good as when she got it. I use Sutherland Welles original high gloss tung oil and reduce it with food grade di limonene orange thinner for the first coat then use it full strength for successive coats. I usually do 4 to 6 coats. I allow at least a month cure time before I let a bowl go to a new owner. I tell them it's listed as food safe but the ultimate decision is theirs because as stated in other threads different people react differently to different products.

 

[Gord Cameron]

Lou, I’ve been experimenting with Tallahassee pure tung oil. I was wondering how durable it is for food bowls. I’d appreciate your thoughts.

I've been making some food contact products lately. Was going to finish with food safe mineral oils, but, I am a fan of tung oil. I don't think pure unthinned tung oil will penetrate well, though.... Anyone know if there are food safe mineral spirits it could be thinned with for deeper penetration?

Tung oil is the most resilient oil finish, so it is a good option for a bowl finish. Pure tung oil; that is, pure, unmodified and unthinned tung oil--can build to a very durable finish, but it is not the best way to work with tung oil; some would say it is not a good way at all. Pure tung oil is thick and difficult to apply, and it takes forever to cure. Polymerized tung oil cures much more quickly and cures to a more resilient finish.

Polymerized tung oil is often (though not always) thinned with solvents, typically mineral spirits, which aid in application, penetration and drying time. While I consider a tung oil finish that has been thinned with mineral spirits to be food safe when cured, others worry about this, and so to answer Jon's question, you can get polymerized tung oil that is thinned with citrus-based solvents. The one I like is the Sutherland Welles Botanical Polymerized tung oil. It is available in various gloss levels (which result from different solvent proportions, not matting agents), or you can buy the high gloss and the citrus solvent separately and mix your own gloss level.

You can get a very good looking and durable finish on a bowl with this SW finish. I don't think it is any more food safe than the normal (mineral spirits thinned) SW polymerized tung oil, which is my go-to finish for most things, but people who worry about finishes that contain products like mineral spirits feel better about citrus solvents, and in my experience both SW finishes behave the same. So, for a few dollars more a quart, I am willing to use the botanical line for bowls and plates and cutting boards. And it makes the shop smell nice for a few days.

 

[Lou Currier]

I've been making some food contact products lately. Was going to finish with food safe mineral oils, but, I am a fan of tung oil. I don't think pure unthinned tung oil will penetrate well, though.... Anyone know if there are food safe mineral spirits it could be thinned with for deeper penetration?

Pure tung oil doesn't need to be thinned. I do it solely for the faster drying time. I have also used it without thinning on salad bowls and it penetrates very well but takes at least 72 hrs of drying time from the last coat.

 

[Lou Currier]

Thanks for the not about DNA vs. mineral spirits.

Sounds like buffing is really what brings out the shine. I have the beall three wheel system. What buffing compounds do you use? Trip and WD, or something else?

I just use the white buffing compound.

 

[Gord Cameron]

Re: buffing a tung oil finish...you are likely to get a noticeably better result if you wait until the finish is fully cured before buffing. You want the hardest possible surface so that you are polishing, not smearing, the finish. Even with polymerized tung oil (or tung oil based varnish), I wait a week or two after the last coat before buffing. If the surface has come out nicely I go straight to a fine buffing compound (I use Vonax, but this is roughly the same as the white diamond compound in the Beall system, just less white, so less of an issue with open-grained woods). If the surface needs it, I start with the tripoli. I always clean the surface with isoproyl alcohol or DNA after buffing; this will take away a bit of the shine by removing the wax that was in the buffing compound, so I complete the surface with a coat of microcrystalline wax.

Also, note that polymerized tung oil cures harder and thus will buff better than even fully cured un-polymerized tung oil. I don't use un-polymerized tung oil, but if you wait the required weeks between coats of un-polymerized tung oil for the proper cure (tung oil should be allowed to cure, not just dry, between coats), then wait for the full cure of the last coat, it might buff up OK. But you risk leaving the completion of the task to whoever inherits your shop.

 

[Steve Tiedman]

Buffing after a pure oil finish- I am not convinced buffing does anything to a pure oil finish. Pure tung, pure linseed, pure walnut oil, etc., when following the directions, are not creating a film finish on the surface of the wood. Oils penetrate the wood, they do not build a surface on top the wood for you to polish. (If the oil is absorbing, it's not leaving a film surface. If you apply oil, wait, and wipe to the mfr. instructions, you aren't getting a film finish. You'd need to apply coat after coat after coat, many coats beyond the coats that penetrate, and allow them to fully cure on the surface, before you'd be actually buffing cured oil.)

If you are wheel buffing with abrasive waxes after 2 or 3, or even more coats of pure oil, you're buffing the wood itself, not the oil finish. Generally speaking, abrasive wax power buffing is meant to polish cured resinous top coat film finishes, not the surface of the oil-impregnated wood.

Polymerized oils are not going to cure harder than non-polymerized oils (that is, either version before application onto wood and other surfaces). Using heat or chemicals to start the oxydation and polymerization process of the manufactured oil only shortens the cure time of the oil once on the wood and exposed to constant oxygen. It does nothing to make the oil molecules harder than the oxidation-polymerized oil molecules when the polymerization process takes place in the wood. Oil molecules are oil molecules.

 

[Jonathan Silwones]

Polymerized oils are not going to cure harder than non-polymerized oils (that is, either version before application onto wood and other surfaces). Using heat or chemicals to start the oxydation and polymerization process of the manufactured oil only shortens the cure time of the oil once on the wood and exposed to constant oxygen. It does nothing to make the oil molecules harder than the oxidation-polymerized oil molecules when the polymerization process takes place in the wood. Oil molecules are oil molecules.

All the research I've ever done indicates this is true. Thanks Steve.

 

[Gord Cameron]

Steve, while it is doubtless true that, as you say, it takes a number of coats of tung oil to create a film finish, it is certainly possible to do so, and indeed it used to be quite a common method of putting a film finish on fine furniture. If I were aiming to build a film finish I would likely use a tung oil - varnish blend, to save time and get the extra durability of the resin in the varnish, but I have often created a film finish (with a decent sheen) with just tung oil. It is a common misperception that an oil finish has to be one that is "in the wood" and not on the surface. It has the advantage of being beautiful and more natural when it has not built to a film finish, and that is how I prefer it, but it does not take long to get a good film finish with straight tung oil.

As for buffing with abrasive waxes, such as with the Beall system, I would say that polishing a cured resinous surface is by far the less common use of abrasive waxes. I do it, but it is tricky and requires a long wait for the full cure, but many woodworkers take bare wood to the tripoli and white diamond wheels to polish the wood, then add a coat of carnuba for a nice gloss and a bit of protection. I don't do this, but in our club there are some members who do only this for work that is not going to experience handling or wear. An even more common approach is to put some sealer on bare wood and then go to the buffing wheels where again, the main thing being polished is the wood. Finally, the core application of abrasive waxes in the form of pastes, such as Yorkshire grit and the like, is to apply them to bare wood, or maybe lightly sealed wood, and get a polished wood surface. So, while Jon's question was about a gloss finish, which would typically involve a film finish, buffing a piece that has a few coats of tung oil on it is a very reasonable approach, and sometimes the workflow that I follow.

Does polymerized tung oil cure harder? Every informed discussion of tung oil finish will state that it does; that is, it not only cures faster, but harder. I use polymerized tung oil primarily for the faster curing, not the hardness, but I have only ever heard the view that polymerized tung oil cures harder.

A quick Google search will get support for this, and I have never seen anyone say the two cure to the same hardness until this thread. I am always a bit suspicious of vendor's claims, but Walrus Oil sells both pure (un-polymerized) tung oil and polymerized tung oil, and spends a lot of space selling the virtues of pure tung oil, but this is their fairly compact statement to the effect that polymerized tung oil cures harder:

Durability: Polymerized Tung Oil has an edge in durability over Pure Tung Oil. It cures to a harder, more resilient finish that stands stronger against daily wear and moisture, making it an excellent choice for dining tables, cabinetry, bar tops, kitchen countertops, and hardwood floors that see regular heavy use. It retains all of tung oil's renowned water resistance and adds an extra layer of surface toughness that's well-suited to high-traffic applications.

Polymerized Tung Oil vs Pure Tung Oil

In the past few years Walrus Oil's Tung Oil product line has earned best-seller status, trusted for being all natural, 100% pure, and void of any additives. In 2025 we expanded to Polymerized Tung Oil, which is strictly heat-bodied and contains no chemical driers.

walrusoil.com

I have an open mind here, so if there is some authority against the common view that polymerized tung oil cures to a more resilient finish, I would like to look at it. I would still use polymerized tung for the faster curing, and would use a blend with resin if I were after serious durability, but I am curious about the science here.

 

[John K Jordan]

Buffing after a pure oil finish- I am not convinced buffing does anything to a pure oil finish.

Don't know about pure tung oil, but often use a non-pure oil like "danish" (One recipe is linseed, poly, mineral spirits)
Buffs nicely if the procedure is followed and the wood is good.

Turn and smooth wood to 400 grit. Fill grain if needed.
Day 1: Saturate the bare wood with "danish oil". Some immerse or soak the wood in a plastic bag with oil. Reapply spots where the surface says it needs more. When saturated, wait 20-30 minutes and wipe off any on the surface, let dry overnight.
Day 2: Again apply as much "danish" as the wood will take, wipe of after 20-30 minutes, let dry overnight.
Day 3-10: Repeat, If I decide its the surface will benefit, wet "sand" with 0000 steel wool or 800 grit paper.
Day 11: Begin the two week wait time.
Day 18 or later:
Beall buff lightly with compound. I use Vonax. I quit using tripoli and white diamond.
Gently apply carnauba wax with Beall wheel and polish
Apply microcrystalline Renaissance wax with soft cloth, let dry, buff by hand with soft cloth. Repeat as needed.
Seems to build and polish nicely. Fortunately doesn't give a mirror gloss so I don't have to end my existence.

Maybe it's the poly that builds the layers.

 

[Gord Cameron]

John, your process is similar to mine, though the "Danish oil" I use when I want some varnish and mineral spirits in with my tung oil is the Sutherland Welles Wiping Varnish.

On the point about polymerized tung oil curing harder, I have been noodling around the internet and still I am only seeing statements (including by Bob Flexner) that polymerized tung oil cures harder than un-poymerized tung oil. Here is what I have found:

Again, with the caveat that vendors are not necessarily experts about the stuff they sell, Lee Valley, which sells both pure (un-polymerized) and polymerized tung oil, says that polymerized tung oil cures harder:
Tung oil has been around for thousands of years, although polymerized tung oil is relatively new. It is tung oil that has had its chemical nature changed by heating, allowing the oil to dry faster, cure harder and bond better.

Bumblechutes might be more suspect because they only sell polymerized tung oil, but for what it is worth, here is what they say:
Wood finish manufacturers discovered that by pre-treating tung oil in certain ways, they could speed up its drying time and even make the cured finish harder – without adding chemicals. The result is known as polymerized tung oil.

Bob Flexner is a pretty authoritative voice for many woodworkers. He believed that polymerized tung oil cured harder. Here is a statement he made in a Popular Woodworking article about tung oil finishes:
Then a product called polymerized tung oil started getting a lot of attention. It’s different than regular tung oil because it is put through a cooking process that changes it chemically, making it cure much faster, harder and glossier.

Explaining Polymerized Oil | Popular Woodworking

A reader of my blog asked me to explain what polymerized oil is. So here goes. On one level the explanation is incredibly simple and on another it’s representative of all that makes finishing and…

www.popularwoodworking.com

 

[Steve Tiedman]

Hi Gord. Your last statement is key- where is the science behind the claim of durability between raw oils and manufacturer's marketing claims of greater durability from their polymerized oil? User support of this claim is anecdotal at best. (Edit- and I'm a big fan of Bob Flexner and his great book.) Now, I've never gone looking for scientific, evidence-based data supporting the claim (frankly, because until this discussion, I've never rationalized the claim in my own mind, I've only ever considered polymerized oils to be faster curing, not more durable), but if 3rd-party lab analysis comparing the two versions of the oils exists, and the analysis shows that I am to stand corrected, then I will gladly eat that humble pie.

But if the claim of polymerized oil being more durable, more protective than raw oil (both being given the full opportunity to cure from a liquid to the solid state) is demonstrated to be true, I'd bet, or better yet guess, that the polymerized oil has the better chance of curing on the surface of the wood (because some of those in-the-can polymerized molecules are too large to penetrate the wood surface, perhaps?).

Please know that I am not debating or doubting users' individual observations or experiences, rather I'm skeptical of the marketing claims and their level of truth based on an understanding of the role served by each ingredient in oil-based finishes. Oils components penetrate the surface. (It's possible, and likely, that some portion of polymerized oil can, to an extent, also remain on the surface and contribute to the surface film, and that could contribute to improved durability of the product.) Resins are too large to penetrate and instead stay on the surface and create a film. Solvents, the amount of them, simply aid in application, depending on the method of application.

Garden variety oil-based varnishes have chemical driers in them to speed the curing/polymerization process after application, and these products will surely have cured oil remaining on the surface of the wood, bound around the resins that will stay on the surface. But if the products to be compared are pure oils, one being raw and the other being polymerized by the manufacturer, I'd want to see the science that supports claims of greater durabilty of the polymerized, and what lead to the greater durability.

Science is fun!

 

[Steve Tiedman]

Don't know about pure tung oil, but often use a non-pure oil like "danish".

Maybe it's the poly that builds the layers.

Yep, it's primarily the polyurethane resins in the Danish oil (a marketing term for thinned varnish) that builds the layers. That surface coat of plastic is what is being polished.

 

[John K Jordan]

. That surface coat of plastic is what is being polished.

It may be difficult to make a definitive statement. From what I've read over the years polyurethane is a wide range of substances, some hard, some flexible, some thermoset (won't melt when heated like many plastics). non biodegradable. To understand the makeup of various "danish" oils might require understanding the nature of the poly component. Even Watco has changed it's formulation several times over the decades. I'm certainly not qualified to describe the composition of the surface coat of any particular "danish: oil. (I always put the word danish in quotation marks since I discovered there is no one formulation. The makers don't say. The MSDS sheets I've looked at are vague.

I know what's in the some user-formulated "danish" oils because the people told me what they mix.

But fortunately, whatever the formulation, I almost never want a mirror gloss. I'm happy with the finishes I get, whether buffed or not. I've been using the same formulation of Watco for many years. With mostly small turning I don't use much. It has never gone bad and needed replacing since I displace the air with Argon.

JKJ

 

[Doug Freeman]

Used AI for difference between raw tung and prepoly tung, as I figured the end result would be the same. It is not. The heat treatment/prepolymerization allows formation of longer chain molecules vs the pure oil state, and the fully cured prepoly oil has more complete bonds vs the raw, making the prepoly tung a bit harder and glossier. It is a slight difference - the prepoly oil does not become a varnish.

My own thoughts (and practice) are that if more gloss is desired just use a varnish. A varnish (which technically includes all the various danish oil varieties since there are resin and/or poly components) does not have to be left as a wet film on the surface - they can be wiped off just like an oil. A varnish, allowed to soak into the surface, provides more mechanical reinforcement of the fibers vs oil, creating an overall stronger structure for the completed piece.

If desired, the varnish will build more film faster vs oil. Adjusting the resin content of the varnish (fraction of oil vs resin) adjusts how thick the resulting film will be.

 

[Gord Cameron]

Used AI for difference between raw tung and prepoly tung, as I figured the end result would be the same. It is not. The heat treatment/prepolymerization allows formation of longer chain molecules vs the pure oil state, and the fully cured prepoly oil has more complete bonds vs the raw, making the prepoly tung a bit harder and glossier. It is a slight difference - the prepoly oil does not become a varnish.

My own thoughts (and practice) are that if more gloss is desired just use a varnish. A varnish (which technically includes all the various danish oil varieties since there are resin and/or poly components) does not have to be left as a wet film on the surface - they can be wiped off just like an oil. A varnish, allowed to soak into the surface, provides more mechanical reinforcement of the fibers vs oil, creating an overall stronger structure for the completed piece.

If desired, the varnish will build more film faster vs oil. Adjusting the resin content of the varnish (fraction of oil vs resin) adjusts how thick the resulting film will be.

Yes, this is what I found too. Apparently, during the curing period, there are forces (scission and hydrolysis) that work against / degrade cross-linking, and it is a bit of a race against time: the prepolymerization of a drying oil gives it a head start, so it completes the cure with a higher degree of cross-linking and thus a harder surface. The pure tung oil cures over a long period, during which the degrading processes result in the reduction in the degree of cross-linking.

Given that finish hardness is relevant to Jon’s original queries about gloss and buffing, I checked with Flexner’s book to see if he had anything more on this topic.

In his book, Flexner seems to be quite clear about the greater hardness of cured polymerized oils, particularly tung oil.

In his first edition (1994), he described (p.71) cured pure tung oil as “Cures soft so shouldn’t be built up on the wood” and cured polymerized tung oil as “Cures hard and glossy”.

By the third edition (2021), he characterises (p.85) the cure of pure tung oil as “Soft and slower than boiled linseed oil—to a satin sheen” and the cure of polymerised tung oil as “Hard and faster than wiping varnish—to a gloss sheen”. He says (p.77) that polymerization “changes the oils that they complete their curing rapidly (faster than varnish) and it makes the oils cure hard and glossy.”

Flexner was such a notorious sceptic about manufacturers’ and vendors’ claims, and such a stickler for evidence and experience, that I give considerable credit to his clearly and repeatedly stated views that pure tung oil cures relatively soft and polymerized tung oil cures relatively hard. It is good to see that the science explains these observations.

 

[Steve Tiedman]

Hi Gord... <snip> but if 3rd-party lab analysis comparing the two versions of the oils exists, and the analysis shows that I am to stand corrected, then I will gladly eat that humble pie.

But if the claim of polymerized oil being more durable, more protective than raw oil (both being given the full opportunity to cure from a liquid to the solid state) is demonstrated to be true, I'd bet, or better yet guess, that the polymerized oil has the better chance of curing on the surface of the wood (because some of those in-the-can polymerized molecules are too large to penetrate the wood surface, perhaps?).
<snip>
But if the products to be compared are pure oils, one being raw and the other being polymerized by the manufacturer, I'd want to see the science that supports claims of greater durabilty of the polymerized, and what lead to the greater durability.

Science is fun!

Okay, quoting myself from message #66 above, I don't think I'm quite ready to serve myself that slice of pie, but if Flexner is among those who can demonstate scientifically (but did he?) that the polymerized tung oil is more durable than raw on the surface of the wood, maybe I can give it a bit more credit, but still skeptically. I won't knock the products at face value, but, like Flexner, don't show me the marketing and the anecdotal stories, show me the science.

If I need a tough surface, though, I'm still going to depend on resin in the oil and consider the options of long oil varnish (pre-made, or the oil-to-resin ratio altered by me) and short oil varnishes.

But you know, in the end, there is only going to be one person who will ever know and appreciate any given finishing technique, and that's the person who applied it to the wood.

 

[Michael Nathal]

Is the buffing the only way you are able to get a glossy sheen? I have the beall buffing system, and I can certainly buff. I suspect that would require some solid curing time, though...

Buffing may not be the only way but it is awfully effective. I use all three wheels. Option A: Wet sanding with walnut or tung oil, cure for an extended time, and then buff. Option B. Oil base poly plus buffing. With porous woods I usually wet sand with walnut oil before applying several coats of poly. The walnut oil needs to cure before applying the poly. I wait at least a week after applying the last coat of poly before buffing. You can accelerate the curing of walnut oil with sunlight or heating to 140 F ("Warm" in my oven) for a few hours. I rarely sand beyond 600 grit: buffing works well increasing the sheen of 400 -600 grit.

 

[Jon Rista]

Don't know about pure tung oil, but often use a non-pure oil like "danish" (One recipe is linseed, poly, mineral spirits)
Buffs nicely if the procedure is followed and the wood is good.

Turn and smooth wood to 400 grit. Fill grain if needed.
Day 1: Saturate the bare wood with "danish oil". Some immerse or soak the wood in a plastic bag with oil. Reapply spots where the surface says it needs more. When saturated, wait 20-30 minutes and wipe off any on the surface, let dry overnight.
Day 2: Again apply as much "danish" as the wood will take, wipe of after 20-30 minutes, let dry overnight.
Day 3-10: Repeat, If I decide its the surface will benefit, wet "sand" with 0000 steel wool or 800 grit paper.
Day 11: Begin the two week wait time.
Day 18 or later:
Beall buff lightly with compound. I use Vonax. I quit using tripoli and white diamond.
Gently apply carnauba wax with Beall wheel and polish
Apply microcrystalline Renaissance wax with soft cloth, let dry, buff by hand with soft cloth. Repeat as needed.
Seems to build and polish nicely. Fortunately doesn't give a mirror gloss so I don't have to end my existence.

Maybe it's the poly that builds the layers.

So, would this basically be a method of diluting poly? Poly is already a combination of oil, resins, and thinners....so if you combined say pure tung oil, poly and mineral spirits....what exactly is that doing, I guess? I guess it isn't necessarily right to say it is diluting. Maybe the amount of resin...adding more oil and thinner would effectively mean you have less resin overall. Is that the fundamental goal of blending like this?

 

[Steve Tiedman]

So, would this basically be a method of diluting poly? Poly is already a combination of oil, resins, and thinners....so if you combined say pure tung oil, poly and mineral spirits....what exactly is that doing, I guess? I guess it isn't necessarily right to say it is diluting. Maybe the amount of resin...adding more oil and thinner would effectively mean you have less resin overall. Is that the fundamental goal of blending like this?

Hi Jon, pure tung oil, Minwax gloss polyurethane varnish, and hardware store mineral spirits, mixed equally, is exactly the "wiping varnish" or "Danish oil" brew I used for many years when I started turning. And honestly, just thinning your locally available oil based varnish, the stuff meant for brush application, on a 2:1 or 1:1 varnish:mineral spirits blend will net you wiping varnish. For funzies, do these same ratios with spar varnish (varnish that has a higher concentration of oil) and let's then call it Danish oil. May as well, since Danish oil is a vague yet exotic sounding name for thin viscosity varnish blended for wiping. Even more silly is "teak oil". Sure, blended specifically for teak, uh-huh...

You can't go wrong on any of these blends, they are all compatible and can be mixed however you choose. Have fun with it, see how they turn out. The wood won't care, it's dead anyway.

Throw good quality gum turpentine in the mix rather than mineral spirits. It evaporates a bit slower and may provide you more working time, if needed.

 

[Doug Freeman]

So, would this basically be a method of diluting poly? Poly is already a combination of oil, resins, and thinners....so if you combined say pure tung oil, poly and mineral spirits....what exactly is that doing, I guess? I guess it isn't necessarily right to say it is diluting. Maybe the amount of resin...adding more oil and thinner would effectively mean you have less resin overall. Is that the fundamental goal of blending like this?

Yes, mixing regular poly or spar poly varnish with solvent is diluting. It is reducing the amount of solids left after all the solvents have evaporated. Spar varnish diluted with solvent is basically "danish oil" - spar is called a long oil varnish, ie has a higher amount of oil vs resin compared to a regular varnish (most all of them today contain urethanes). We don't know the exact composition of all these different types of varnishes (% of exactly what oil, what resin, what solvent) mfrs are tight lipped about it, the %'s in product, technical or safety data sheets are broad (5-20% of x) but generally we can get some idea of what the oil, resins, and solvents are.

For turned items, IMO urethanes in varnish have gotten a mythological bad rap. In flat work, furniture, house trim, etc, relatively thick films of finish are left on the surface, and urethanes can be a bit more cloudy vs the old phenolic and alkyd resins (but urethanes are much tougher). Turned items typically have almost no surface film thickness. Its more of an "in" vs "on" the wood application, and urethane varnishes are great for this. They have a much higher mechanical strength vs any of the oils once cured, which reinforces the strength of the wood.

There is much debate over the oil use in a varnish, mainly linseed vs tung. The moisture resistance of a varnish or oil is a function of the film thickness and bond strength. While tung oil has a slight advantage over linseed, once resins are in the mix (a varnish), the bond strength increases dramatically, and any advantage of tung vs linseed pales in comparison to what the resins bring to the party.

Its all in the application of the finish. An oil based varnish can be thinned and treated just like an oil - flood the surface, keep it wet 20-30 min, wipe it off. Apply as many coats as desired in this manner, though a 3rd coat generally won't add much in terms of absorption into the wood. More thin coats are for building film thickness and gloss.

I follow much the same finishing schedule that @John K Jordan details above, and use Minwax (gasp! cheap junk!) Helmsman Spar varnish semi gloss diluted 1:1 with paint thinner (slightly more volatile vs mineral spirits, which is a bit oilier). I've used many different brands over the years and haven't found any advantage to the more expensive brands, but they do work much the same. I do sand to a higher grit, and take advantage of the "gel" stage of the varnish, working the heavier bodied finish over the surface, then wiping/buffing it off. 1 coat is usually enough, but it's easy to do another if needed.

 

[Don Schwartz]

As I understand it, tung oil is as much a marketing name as Scandinavian or Swedish oil - and nything labelled simply as tung oil can be assumed to be an oil/varnish blend. Only 'pure tung oil' can be taken to be pure.

In some ways, you might be best off to blend your own oil/varnish mixes for satin/gloss etc using a pure tung oil and your preferred varnish in varied proportions. in this way you only need to buy two products and mix them as you see fit for a particular application. When seeking a desired lustre for a specific piece, you can apply a first coat at the the mix you think best, wait til it dries, and decide whether and how to adjust by adding more oil or varnish to achieve more or less gloss. If the gloss starts out too high, it can be cut back with a fine abrasive and followed with a mix with more oil. Add more varnish if it's too dull.
fwiw
Don

 

[Jon Rista]

Yes, mixing regular poly or spar poly varnish with solvent is diluting. It is reducing the amount of solids left after all the solvents have evaporated. Spar varnish diluted with solvent is basically "danish oil" - spar is called a long oil varnish, ie has a higher amount of oil vs resin compared to a regular varnish (most all of them today contain urethanes). We don't know the exact composition of all these different types of varnishes (% of exactly what oil, what resin, what solvent) mfrs are tight lipped about it, the %'s in product, technical or safety data sheets are broad (5-20% of x) but generally we can get some idea of what the oil, resins, and solvents are.

For turned items, IMO urethanes in varnish have gotten a mythological bad rap. In flat work, furniture, house trim, etc, relatively thick films of finish are left on the surface, and urethanes can be a bit more cloudy vs the old phenolic and alkyd resins (but urethanes are much tougher). Turned items typically have almost no surface film thickness. Its more of an "in" vs "on" the wood application, and urethane varnishes are great for this. They have a much higher mechanical strength vs any of the oils once cured, which reinforces the strength of the wood.

There is much debate over the oil use in a varnish, mainly linseed vs tung. The moisture resistance of a varnish or oil is a function of the film thickness and bond strength. While tung oil has a slight advantage over linseed, once resins are in the mix (a varnish), the bond strength increases dramatically, and any advantage of tung vs linseed pales in comparison to what the resins bring to the party.

Its all in the application of the finish. An oil based varnish can be thinned and treated just like an oil - flood the surface, keep it wet 20-30 min, wipe it off. Apply as many coats as desired in this manner, though a 3rd coat generally won't add much in terms of absorption into the wood. More thin coats are for building film thickness and gloss.

I follow much the same finishing schedule that @John K Jordan details above, and use Minwax (gasp! cheap junk!) Helmsman Spar varnish semi gloss diluted 1:1 with paint thinner (slightly more volatile vs mineral spirits, which is a bit oilier). I've used many different brands over the years and haven't found any advantage to the more expensive brands, but they do work much the same. I do sand to a higher grit, and take advantage of the "gel" stage of the varnish, working the heavier bodied finish over the surface, then wiping/buffing it off. 1 coat is usually enough, but it's easy to do another if needed.

Thanks for the info. Diluting with a thinner is clear to me. Its the addition of oil as well, that made me wonder what the goal was. If you add both oil and thiner to poly, the thinner is ultimately going to evaporate, while the addition of oil will effectively reduce the ratio of resins to oils, right?

When it comes to which oil, my preference these days is Tung, as I've never liked the strong yellowing that linseed generally imparts. Especially for lighter woods, I prefer the color with tung over linseed. I suspect it really doesn't matter which oils you use? I once emailed Minwax about what oils they use, and the response was it varies, and its often very different oils than we normally buy in cans like linseed or tung....all plant oils as far as I could tell, maybe even mostly grass seed oils, but it was interesting that they did not seem to use linseed or tung in their minwax products (at least, not at the time, guess that was a few years ago.)

So I guess the remaining question is...if we create "Danish oil" by blending more oil, thinner and an existing varnish....the net change is resin ratio. And is that the purpose and the goal? To reduce the amount of resins in the final finish?

 

[Gord Cameron]

Thanks for the info. Diluting with a thinner is clear to me. Its the addition of oil as well, that made me wonder what the goal was. If you add both oil and thiner to poly, the thinner is ultimately going to evaporate, while the addition of oil will effectively reduce the ratio of resins to oils, right?

When it comes to which oil, my preference these days is Tung, as I've never liked the strong yellowing that linseed generally imparts. Especially for lighter woods, I prefer the color with tung over linseed. I suspect it really doesn't matter which oils you use? I once emailed Minwax about what oils they use, and the response was it varies, and its often very different oils than we normally buy in cans like linseed or tung....all plant oils as far as I could tell, maybe even mostly grass seed oils, but it was interesting that they did not seem to use linseed or tung in their minwax products (at least, not at the time, guess that was a few years ago.)

So I guess the remaining question is...if we create "Danish oil" by blending more oil, thinner and an existing varnish....the net change is resin ratio. And is that the purpose and the goal? To reduce the amount of resins in the final finish?

Jon, the goal is not to reduce the amount of resin in the finish, though that is one of the necessary consequences. The blend of oil and varnish will have some of the qualities of each finish alone: the oil will make the finish softer and less glossy, and make the finish penetrate more and build more slowly than the varnish alone; the varnish will make the finish harder and more glossy and build more than the oil alone. Because these characteristics might be desirable or not depending on the wood and the targeted outcome, you can blend to meet the case at hand. Adding thinner--that is, more than is already in the varnish--is optional and often not part of an oil-varnish blend. Thinner will make the oil-varnish blend penetrate more and spread a bit more easily, but it will not build as quickly.

 

[Steve Tiedman]

Or, from my recent thread, maybe you could concoct a method to add dammar resin (very finely powdered, probably, a mortar and pestle could probably grind it down super fine) to a pre-made varnish recipe, see what happens. Experimenting is half the fun.

Thread 'dammar gum varnish (high gloss, natural resin)' https://www.aawforum.org/community/threads/dammar-gum-varnish-high-gloss-natural-resin.25580/

 

[Michael Nathal]

Jon, the goal is not to reduce the amount of resin in the finish, though that is one of the necessary consequences. The blend of oil and varnish will have some of the qualities of each finish alone: the oil will make the finish softer and less glossy, and make the finish penetrate more and build more slowly than the varnish alone; the varnish will make the finish harder and more glossy and build more than the oil alone. Because these characteristics might be desirable or not depending on the wood and the targeted outcome, you can blend to meet the case at hand. Adding thinner--that is, more than is already in the varnish--is optional and often not part of an oil-varnish blend. Thinner will make the oil-varnish blend penetrate more and spread a bit more easily, but it will not build as quickly.

This is a good summary. This leads to another strategy: use a oil or an oil blend for the first coat, to achieve the penetration and make the grain/figure "pop". All subsequent coats can be 100% varnish or another film former to achieve higher gloss and higher protection.