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General finish for wood that might get a little wet?  RSS feed

 
William James
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Having trouble with a wood project.
I sanded everything down and now the time has come to choose what to do with the wood before putting it to use.

I got these very long and very thick planks for a microgreen production shelving unit. So, the wood shouldn't actually come into contact with rain, but there might be a little humidity under the plastic nursery trays and there will be a drop of water here and there.

I was thinking linseed oil, but having read some John Elliot's comment on the drying process, I'm not sure anymore I want to go that route. I'm doing this all in a warehouse, so there's little sun and not much ventilation.

I'm trying to find an alternative to whatever the hardware store is going to tell me to use. The objective is to get something similar to the natural wood tone that there is now and have it be somewhat waterproof.

Thanks,
William
 
William James
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Found a local supplier of non-toxic wood finish. Yay.
 
Jack Edmondson
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William,

Good old fashion Varnish is a great sealer and non-toxic. It is recommended for finishing wooden children's toys, so it is safe.
 
William James
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Anyone ever heard of soap?
Someone told me of Marseille soap as a water repellent varnish.

How about melting it down (with oil?) and painting it on.
W
 
William James
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The other idea I had was beeswax. I imagine that repels water well.
W
 
Rus Williams
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Yeah, beeswax mixed with turpentine is pretty natural and allows the wax to soak into the timber a bit more. Beeswax on its own is only really a surface treatment, and needs some pretty serious working in to really work properly.
Beeswax is a furniture finish, so I would suggest that linseed oil , (wipe on, wipe off. Repeat a time or two) would be easier and quicker for your situation.
 
Michael Bushman
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Location: Sacramento, CA
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Most of what people know about finishing wood is myth.

Finished called "linseed oil" have about as much variety as things called "organic" ranging from pure oil to pure crap. SOME but not all linseed has heavy metal drying agents, same goes for Danish oil. Linseed oil is not as waterproof as tung oil but neither are as waterproof as polyurethane.

Many finishes have solvents and are toxic when raw but safe and inert once dry. Many "food safe" and "salad bowl" finishes are in fact polyurethane with additional thinning agents to allow for two things, the first being they penetrate well and second that they are slow to build up a surface film and are thus easier to apply on a curved surface and look more like an oil finish.

If wood will be in contact with moisture, the two best ways to keep it from rotting are to either leave it all natural so that the water it absorbs can evaporate or finish both sides with a film finish like polyurethane or varnish and ESPECIALLY the end grain.

Varnish is used on boats because it used to be the best at surviving in the sun and it is flexible so that as the wood expands and contracts with changes in moisture, it didn't crack. Its a PIA to apply, its slow drying time means dust and such has lots of time to settle into your finish.

If I was making a wooden rack that was going to have water but I wanted to keep it looking great, I would find a brand of finishes that had both a salad finish and a full strength polyurethane, both cans are the same finish but the salad bowl finish would be my first few coats to get as good a penetration as possible, then three coats of the full strength poly. You can duplicate the same technique by thinning a finish but then you need thinner, so pick your path.

Another note on finishes, you will often see the same finish sold with "satin", "semi-gloss" and gloss. The way satin and semi-gloss are made is basically by putting dust into the finish. So a thick coat of satin has that horrible plastic look. Satin is great at hiding imperfections in the finish but the trick to getting it to look good is to use all gloss to build the finish and use a final coat (great time for a spray can) of satin so you get the clarity and depth of the gloss but the mistake hiding effect of the satin.

A note on polyurethanes. It is a plastic finish and once it dries, it is like a layer of saran wrap. If you add a coat when the finish is still soft, you do not need to sand as the solvents in the new layer will bond with the previous layer. Once it is more on the dry side, you sand to remove the imperfections but also to create a mechanical bond as there will no longer be a chemical one. True shellac and lacquer create a single layer as their solvents disolve the previous layer and bond chemically and so no sanding is needed between coats.
 
Jay C. White Cloud
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Hi William,

I don't know how this post thread of yours got past me..??...sorry about that...

There are a number of really good post here on Permies.com about natural wood finishes...I have written a few of them myself...

I have used the same general blend for over 30 years to very good effect both indoors and out. It is a blend of Pine Rosin, Tung Oil, Flax Oil, Beeswax, and Citrus oil as the carrying and penetrating agent that "thins" the other materials down. The amount of citrus oil takes it from a "paste finish" (with extra pine rosin and beeswax) to a true multi coat penetrating oil...We add a u.v stabilizer to the exterior forms of it.

You can get it at: Heritage Finishes They sell the natural food grade oils or pre blended materials. The owner, Autumn Petersen..(please feel free to contact her)...is a grand person to speak with...

I have heard, read and seen my grandmother's version of "soap finishes," they are not durable as other forms of natural oil finishes...

I recommend only pure natural materials with no additives and "food grade" if you can get it.

>>>

Hello Michael B.

Michael Bushman wrote:Most of what people know about finishing wood is myth.


I could agree with that to some degree...especially if speaking of "modern woodworkers" and "painters." They have lost (or never learned) the art of making there own paints and finishes...

Michael Bushman wrote:...Linseed oil is not as waterproof as tung oil but neither are as waterproof as polyurethane.


This is kinda subjective in perspective in my experience. I have a number of old articles (pre internet) and studies from "material science" types that have examined both modern formulations and old natural finishes as well. The only thing to actually reach a level of "water proof" in the 85% to 95% range was 3 or more coats of "marine grade epoxies" of several types, and the only thing to achieve 95% to 100% water proof capacity was wood dipped in pure wax twice or more times. Of course these traditional "dipped finishes" are not heat tolerant or very time/abrasion durable.

More than three coats of natural oil blends are actually much more "water resistance" and durable over time than any of the urethanes which, like epoxies, have a tendency to trap interstitial moisture within the wood, and are never as easy to refinish as natural finishes are...

Michael Bushman wrote:...Many "food safe" and "salad bowl" finishes are in fact polyurethane with additional thinning agents...


I have hear and read about some recent applications of urethans for "food surfaces." This is something I have never recommend to students or clients and I suggested before...they are not that much better than natural oils (which have been employed in good effect and service for millenia as have some "rubbed lacers" and are never as easy to refinish. Nor do I personally care for eating off plastics of any type...but I own that is a subjective aversion of my own...

If wood will be in contact with moisture, the two best ways to keep it from rotting are to either leave it all natural so that the water it absorbs can evaporate or finish both sides with a film finish like polyurethane or varnish and ESPECIALLY the end grain.


This one we will just have to take a different view on. In my experience urethanes and epoxies, along with most modern finishes trap moisture within the interstitial zones of wood in almost all applications I have ever seen expose to continued moist environments. I recommend "naturally rot resistant species" and only oil finishes and/or natural paints such as lime, casein or tempra based. With Lime being the best performer over time in the "paint" venue. I have worked with woods that are still in service that are over 300 years old and have been parts of "restoration projects" where urethans and epoxies have been used as a "modern finish only to destroy the vintage character and rot the wood...

Michael Bushman wrote:Varnish is used on boats because it used to be the best at surviving in the sun and it is flexible so that as the wood expands and contracts with changes in moisture, it didn't crack. Its a PIA to apply, its slow drying time means dust and such has lots of time to settle into your finish...True shellac and lacquer create a single layer as their solvents dissolve the previous layer and bond chemically and so no sanding is needed between coats.


Actually, from my experience working on and with several traditional Boat Wrights, not all are the same in level of characteristic, or as challenge to apply...Some like the "Asian Lacquers" can be but are also very durable as well, some lasting over centuries even underwater. Many artifacts have been found where the wood is gone inside and all that is left is the finish.

All in all, it is a personal choice, but being a traditional woodworker and timber framer (and this being a "permi" type forum focused on "natural modalities,") I strongly recommend against any "plastic finishes" from not only a "performance standpoint" but also an "environmental one" as well. The industries that produce this "modern urethans" and other paint finishes are some real series polluters...with huge carbon foot prints in general...

Regards,

j
 
Chadwick Holmes
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Location: Volant, PA
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Shellac finishes are a product of a beetle mixed with alcohol as the solvent, using a waste product and an evaporative is a good choice as well....

Buy shellac flakes and the remaining portion is shelf stable forever in a jar....

Boring tips from a dorky master carpenter!
 
Chadwick Holmes
Posts: 618
Location: Volant, PA
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forest garden fungi goat trees wofati woodworking
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Now I’m not going to waffle on in great detail about the process’s of polishing but a little knowledge will help.. The primary ingredient of French Polish is shellac. A tiny female Lac beetle secretes this amber coloured waxy resin as it gorges on the sap of trees. Found in India and Thailand this insect is farmed for its protective covering of shellac but only after it has finished its life cycle. You see, we are very ‘green’. The flake shellac is then dissolved into a solution by adding industrial alcohol/methylated spirits. The French Polisher would apply this to his chosen piece by the use of a carefully folded ‘fad’ which is a large palm sized piece of cotton wadding which has been soaked or ‘charged’ with polish and meths. Similarly a Beautician would apply it to your finger nails for a small fortune!
 
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