# Experiment: Waterproofing With Pine Tar



## FarmerintheWoods (Mar 3, 2017)

There's a lot of debate on the web about how to 'waterproof' wood. It's generally agreed that wood cannot be waterproofed, although there are heroic measures that seem to work well.

One time-tested, historic method to keep wood dry/stable/protected was the use of pine tar and placing the treated wood in summer sunlight, using a heat gun, etc.

Here's my experiment with using pine tar for waterproofing. All samples have been sanded down to 110 grit. Surface treatments were slather it on, let it rest 5 minutes, then wipe it down, then let it rest 24 hours. All treatments were dry to the touch after one hour.

The top row, left to right, is (1) naked black cherry, (2) black cherry with 50-50 paint thinner & BLO, and (3) black cherry with 4:4:1 BLO:Turpentineine tar.

Bottom row, left to right is (4) black cherry, equal parts BLO, turpentine, and pine tar, (5) same mix with mulberry, (6) same mix with black walnut, and on the far right, same mix on white ash.

To test for waterproofness, I touched my finger into a cup of water, and put one drop on each wood sample. (Though not on the naked cherry sample.)

Results: After one hour, all samples absorbed all the water, and all were splotched.

One remarkable thing about this experiment: the pine tar/BLO/turpentine 1:1:1 mix is very dark, but doesn't darken the wood more than the 1:1 BLO/paint thinner mix.

Here's the samples:










Here's the pine tar mix:


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## TObenhuber (Jan 15, 2014)

I think an interesting test would to be leave those samples outside for 6-12 months. Then check to see how they look every two weeks. Taking a picture each time. I think water proofing is usually used for boats and outside projects.

What do you think?


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## JamieAB (Apr 14, 2016)

You should chuck in a piece of Sapele. A company I worked for used that wood in the thrust decks for AC/DC supposedly under the premise that it was hardier against water damage.


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## FarmerintheWoods (Mar 3, 2017)

What I'm trying for is to get wood movement due to change in moisture as close to zero as possible, but without excessive time and trouble.

The 1:1:1 recipe dates back to at least WWII, when it was used to 'waterproof' gunstocks. Using pine tar for waterproofing dates back to the Vikings.

I'm trying to work out how us 'modern' people can use this old tech.

BTW, I took all the samples and sanded them down to bare wood, and re-coated them with 1:1:1 and left them until tacky, and then re-coated again. More saturation might be the trick.

The remarkable thing so far is that this mix works well as a finish. Polyurethane and other similar things do not tempt me.


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## wormil (Nov 19, 2011)

I would think that to waterproof, the pine tar would need to be visibly thick. Have you tested pine tar alone to see if it's waterproof? It looks nice, how does it feel?


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## FarmerintheWoods (Mar 3, 2017)

At room temperature, the pine tar (Bickmore brand) is about the same consistency as maple syrup. When it's dry (the 1:1:1 mix) it's hard and smooth, with no tackiness. It's not as smooth as polyurethane, though, it feels more like natural, unfinished wood.

I'll be trying the water droplet test again in a couple hours, and depending on results, try a 1:1 BLO/tar and 1:1 turps/tar. Then perhaps a pure tar experiment. One thing I've established for sure, though: pine tar is a very effective air freshener! Makes the whole house smell like a pine forest.


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## wormil (Nov 19, 2011)

I would love it then. Pine Sol is my favorite cleaner


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## FarmerintheWoods (Mar 3, 2017)

The results of another round of the water droplet test are in. I re-used all the original wood samples. Everything blotched again, but more slowly. Except for the white ash. The droplet on the white ash evaporated without a trace.

Next up: test for serious saturation: samples slathered and stuffed into a plastic bag.


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## FarmerintheWoods (Mar 3, 2017)

Once again, I used the 1:1:1 pine tar/BLO/turpentine mix. Wood samples were black walnut, black cherry, and red mulberry.

This time, the wood samples were thickly coated and wrapped in plastic to make normal drying impossible. After two hours, I removed the samples and they were still completely wet. I wiped them down and set them out to dry. As before, they felt dry to the touch in 2 hours. Mostly.

The black walnut began 'leaking' wood treatment from the end grain, shortly after being set out to dry, and that continued until this morning. Also, the black cherry absorbed so much that the sample moved, and developed a noticeable curve. It used to be a rectangle every which way.

The water-droplet test showed that this treatment slowed absorbtion of water substantially. Even so, all samples splotched, and absorbed water faster than it evaporated.

The recipe I'm working with is sometimes called 'boat soup' by (modern-day) people who build wooden boats and want their hulls etc. to be waterproof. This isn't working very well.


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## Snipes (Apr 3, 2012)

So i'm wondering what exactly your trying to figure out with this experiment? Soaking all your projects in pine tar doesn't seem very feasible. maybe your just passing time?


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## FarmerintheWoods (Mar 3, 2017)

All the wood finishing I've done since 1972 has been oil stain and polyurethane. Or sometimes just polyurethane. The stain is great, the poly is just plastic, and if you scratch it, it's marred. I want something better. Something that's not on the wood, but in the wood, and is good for rain or shine. Something that's good enough, say, for shovel handles or axe handles but works well with a range of native hardwoods.

White ash is a cinch. Although, moving it across state lines is an issue with the emerald ash borer running around. I have a lot of hackberry, which has its own charms, but the wood is loaded with silica. It takes a nice finish and glitters because of that. But, it doesn't like to take stain, and it dulls tools really fast.

So I'm trying to get something better for the other woods I have: black cherry, black walnut, and mulberry. I'm tired of polyurethane and looking for options.

There are a number of non-natural recipe options out there, that I haven't tried, such as mixtures of used motor oil, power steering fluid, and automatic transmission fluid. Some recommend adding a bit of roofing tar for color. I'd rather not go there because the legal status of wood products with treatments like that would be dubious at best. In California for certain.

I'm now backing up and looking at finishes/solvents that might work with paraffin, but still pop the wood grain/figure as nicely as BLO. But I'm totally open to hearing other recommendations.


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## kelvancra (May 4, 2010)

Rather than paraffin, look to beeswax and a double boiler. Run a search on the Net for that mix. You'll get all sorts of boat hits and Finnish hits.

I've been playing with the same thing, off and on, for a couple years now. My wife's potting bench is the primary test device.


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## ArtMann (Mar 1, 2016)

I don't mean to be too negative but I don't think your experiments are going to verify that a piece of lumber won't take on moisture and change dimensions. The stuff you are putting on the surface will only penetrate a few thousandths of an inch, as you may have discovered from sanding it off. Moisture content in the wood will still change with changes in humidity unless you completely cover it air tight in something like a fiberglass/epoxy laminate and I'm not too sure about even that.


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## kelvancra (May 4, 2010)

I don't think it's negative. Rather, it's just part of what this whole site is about- trying to share information and experience.

On the latter, I hear many say finishes only go in a few thousandths. The problem I have with that is, for example, the gallon of plastic oil, polly or pine tar that went into the boards I was applying one or the other on. Obviously, the material has to be going somewhere, and isn't gassing off.

Of course, in situations where the wood I was applying product to sucked up large quantities of finish, the wood was seasoned and dry. Too, how it soaks in would depend on the wood.

Years back, I was working a six inch slab of redwood with poly. I started off flooding the slab and when I got to an end, I'd go back and flood spots that had soaked in. The process repeated for the better part of an hour and a half. Then, throughout the day, every time I walked by the slab, I'd apply finish where it soaked in.

Toward the end of the day, I dropped my brush. When I knelt down and picked it up, I looked at the bottom of the slab and several spots were wet.

I think I know where the gallons of poly and finish went.

The upside was, even in front of a working fireplace insert, the wood remained pretty stable.



> I don t mean to be too negative but I don t think your experiments are going to verify that a piece of lumber won t take on moisture and change dimensions. The stuff you are putting on the surface will only penetrate a few thousandths of an inch, as you may have discovered from sanding it off. Moisture content in the wood will still change with changes in humidity unless you completely cover it air tight in something like a fiberglass/epoxy laminate and I m not too sure about even that.
> 
> - ArtMann


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## ArtMann (Mar 1, 2016)

Unless your finish is gas sealed, your strategy won't work. The humidity we are talking about is not a liquid. It is a gas. You can't stop the migration of gaseous H2O into and out of a piece of wood with anything that you can easily sand back off. It needs to be thick and solid. If changes in humidity of wood could be prevented with a spray, brush or wipe on finish, then people wouldn't go to such great lengths to design furniture and structures that take into account. It just not as easy as you are thinking.

On the other hand, here is a word of encouragement. If your piece is going to be inside, the relative humidity changes much less than some people think. I live in the super humid Southeast and I monitor the RH inside my house daily. I have seen it as low as 45% and as high as 59% but mostly it ranges much less than that. If you consult one of the many tables that predicts dimensional changes with changes in RH, you will see that the change is small over that range. Some people go way overboard with their concerns with humidity.


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