Talk me out of tung oil for drawer interiors

I've had raw tung oil get a bit stinky when old.... kinda like a dog that has needed a bath for 10 years.  Linseed has a strong odor even when fresh.  I don't find linseed's odor unpleasant, but I don't think I would want it on a drawer.

Shellac is the way to go.  I know you've ruled it out, but I think it's worth a second look.  For this you want what is called button lac.  You can get it at shellac.net.  It dissolves much more easily and quickly in alcohol than does dewaxed flake shellac, and is very good for utilitarian sealing work like this.  It will take several coats but it's the best way.  Mixing is easy, you just need a jam jar, a measuring cup and a cheap postal scale from an office supply store.

For solvent, get some pure ethanol, it's harmless and fully evaporates.  Denatured alcohol is ethanol with a little methanol mixed in so it cannot be consumed and thus avoids liquor taxes.  I typically use that for shellac, but if you are fume conscious you may want to avoid the methanol.  Lately I've not seen denatured alcohol in the local stores where I live, instead it's called "fuel alcohol" and is mostly methanol.  I find that the shellac doesn't dissolve as fully in methanol (as in you can dissolve less shellac before it's saturated).  Though it still works, probably best to avoid that stuff in your case, peace of mind if nothing else.

You can also use water based polyurethane.  More than about 3 coats and you start to see it's kinda milky sheen on the work (unless it's very light color wood).  That's why I prefer shellac.

if I were going to use tung for this, it would be thoroughly mixed with 1% japan drier. 

I've never really had an issue with shellac for drawers, though, and I'm sure i've sprayed Target EM6000 on drawers of something before, but can't remember what. 

You get your pick, I guess - microplastics in the air with target, or denatured alcohol with shellac (or isopropanol).

The solvent in shellac is alcohol. It will evaporate in minutes and leaves no lingering odor or toxicity. Shellac itself is food safe and used as a coating on medicinal tablets for human consumption. You can buy it premixed at any paint, hardware or big box store.

Dave Bair wrote:

You can buy it premixed at any paint, hardware or big box store.

I always forget about that one, good point.  The Zinsser stuff I've used in the past was a pretty thick version, a coat or two would do it easily.  It was basically what I get using button lac too, more user friendly than dewaxed.

"Talk me out of tung oil for drawer interiors"
That's easy. It stinks something like vomit when it's trapped inside an enclosed space with little or no air circulation, e.g., the interior of a cabinet where drawers tend to be. Slainte.

Sgian Dubh wrote:

"Talk me out of tung oil for drawer interiors"
That's easy. It stinks something like vomit when it's trapped inside an enclosed space with little or no air circulation, e.g., the interior of a cabinet where drawers tend to be. Slainte.

that smell can be eliminated with an ethanol wash, but doing so does increase the price of raw tung from about $33 a gallon here to maybe twice that after paying for the ethanol, which is spent into a pee yellow condition and with the fatty acids that stink in it. It may actually be good as a rust prevention wipe. 

it also requires boiling ethanol and tung oil together and then giving it a gentle mix and separating the oil from the mix when done - alcohol goes to the top. Boiling ethanol could be hazardous to anyone who doesn't realize that it doesn't just float away that quickly - the vapors pour over the side of the bowl and are present in a way that a spark even from a drill could be a big problem. 

But compared to making varnish, it's not terribly hazardous. I would guess the free fatty acids remain in the commercial oil because they are useful for moderating/slowing the reaction speed when it's heated. An ethanol wash removes a little over half of the free fatty acids (by cas spec, 4% or less of the volume) and more importantly, the ones that stink.

DavidW wrote:

Sgian Dubh wrote:

"Talk me out of tung oil for drawer interiors"
That's easy. It stinks something like vomit when it's trapped inside an enclosed space with little or no air circulation, e.g., the interior of a cabinet where drawers tend to be. Slainte.

that smell can be eliminated with an ethanol wash, but doing so does increase the price of raw tung from about $33 a gallon here to maybe twice that after paying for the ethanol, 

That all seems like a lot of bother. I reckon it's much easier just to not use tung oil in any shape or form, i.e., pure and/or modified as you describe for the interiors of enclosed cabinets. Better, in my opinion, to just use shellac or even a lacquer such as pre or post cat all of which don't smell unpleasant after a wee while after they've fully off-gassed. Slainte.

Sgian Dubh wrote:

DavidW wrote:

Sgian Dubh wrote:

"Talk me out of tung oil for drawer interiors"
That's easy. It stinks something like vomit when it's trapped inside an enclosed space with little or no air circulation, e.g., the interior of a cabinet where drawers tend to be. Slainte.

that smell can be eliminated with an ethanol wash, but doing so does increase the price of raw tung from about $33 a gallon here to maybe twice that after paying for the ethanol, 

That all seems like a lot of bother. I reckon it's much easier just to not use tung oil in any shape or form, i.e., pure and/or modified as you describe for the interiors of enclosed cabinets. Better, in my opinion, to just use shellac or even a lacquer such as pre or post cat all of which don't smell unpleasant after a wee while after they've fully off-gassed. Slainte.

shellac is my choice, too - unusual constraint at the beginning of this was VOC-free finishes. I use tung oil for other things, but including making varnish. Guess what makes the tung oil stink disappear completely? cooking it together to make a molecule of pine rosin and tung combined, and varnish would be OK, but it's more trouble than shellac and I've never had any trouble with a shellacked drawer, and the repairability is always there if there is one. 

I have such a distaste for the stinky smell, but the whole issue of washing tung oil came up  since it's a necessary part of making good linseed oil for varnish - to get rid of the volatiles and proteins and keep the parts you want. Either that or a harsh cook in a pot full of lead - but that's out of style these days. Bill tells me that the association of danger with leaded finishes like varnish is overblown, but the cooking part with the lead in would definitely be less innocent (vapors) and you get a big pile of litharge to take to hazardous disposal as a result.  my solution to tung was to put japan drier in it so that it cures quickly and deeply in short order and the stink stops. finding that washing it took the stinky part of the FFAs out is a nice byproduct, but some additional research found that they're left in for a reason instead of being completely stripped - tung is really reactive in a cook and probably would go into a run away reaction in some circumstances. 

A one ton pot of exothermic reaction in manufacturing would probably not be good. the old varnish books, old compared to now, but after industrialization, show big vats and guys essentially working around the outside of them with a firehose to slow reactions that could otherwise take off.

Mark Mandell wrote:

With a double penchant for chemistry and cooking, David is never at a loss for good technical advice.

Just don't forget, "Never eat blueberries for breakfast!" according to a top doc and the A.S.P.W.T.S.

Boy do I know almost nothing about chemistry, but fortunately, Bill Tindall knows a lot about it and is willing to answer questions. 

to that end, any time I mention free fatty acids or double oxygen bonds (oxygen double bonds?...the type critical to all of the finishes that dry in sun, heat or oxygen exposure), I'm just parroting what I have learned from Bill. 

I do like the experimenting side, though! It usually yields something unexpected. I washed tung oil seeing if it would result in faster drying or harder curing films. I couldn't tell the difference, except the rancid nut smell that permeated my work are and my office area (adjacent) went away with that. Bill provided the idea for a process that might separate the FFAs - warming ethanol and tung together and then rolling gently in a jar. Actually easier than one would guess, especially if you buy a cheap separator funnel. There is a time component, but it can be done in a minute here and there between something you're actually working on. The separating part just needs time sitting somewhere on its own. 

There is some joy in experimenting and then getting things you weren't looking for - because you often don't get what you were looking for. Hardening steel, all the way up to just making a hard English style chisel out of solid Japanese white #1 steel yesterday really came out of just seeing how bad steel would be before finding a heat treater and sending it off. Unexpectedly never got to sending anything off or even buying a heat treat kiln. it all just falls out of the sky almost if you're just there to catch it.  

Odor free tung oil is just another happy thing that fell from the sky. But a little dangerous to make and probably not suitable information for beginners who never really got a taste of consequences to get a good feel for what's a good risk and what's not.

Shellac is the best option for inside drawers, in my view.  Premixed shellac is fine.  The ethanol solvent will completely evaporate.  

It is interesting that an ethanol wash removes the worst smell from Tung oil.  But have you actually checked that it is low enough for a drawer?  Varnish even after it seems to have cured to the odorless state can still be horrible inside a drawer where slight offgassing can build up.  Shellac doesn't do that.

Japan drier sounds like a better idea than heating with lead oxide, which is more toxic than finish with tiny amounts of lead in it, but even that toxicity is unnecessary.  What you want is a small amount of a transition metal ion dissolved in the finish as a catalyst.  Less toxic metals than lead (manganese, cobalt...) work, and soluble versions of these can be made using 2-ethylhexanoic acid -- probably what's in modern Japan drier.  The amounts of these soluble salts needed are minuscule compared to older methods with direct heating where the acids you remove in an ethanol wash are probably responsible for solubilizing a small amount of the metals from the oxides.

I use klean strip's japan drier, but it appears they have ceased to bottle it. Sunnyside looks to have the same thing. 

And, you are correct, I have not put any of the tung in an enclosed box. it does still have a trace of smell after the hot ethanol wash when it cures, but it is almost a sugary smell. no clue if that's from the combination of the finish and wood or just the wood. I wouldn't be surprised if something occurred over time from degradation or aging that made it stinky. 

I think I mentioned the 20 year old polyurethaned cabins at deep creek above - there will never be a point that they don't stink if they are closed for even a few days, I guess as the finish cures initially but then never really is 100% stable - it's degrading and giving off stink. The cabin owners who let us stay there for a weekend said "you'll notice a smell that smells like wood when you go in, because nobody has been there for a couple of weeks". 

it wasn't wood! 

i've got a bunch of cigar boxes here that are spanish cedar and that seal well. I'll tung oil one and put varnish in the other (not polyurethane) and see if they stink. 

there's a lot of hysterical advice about how toxic japan drier is, but Bill informed me that's overblown for a casual user. I love the stuff - but I hope the three drier combination (magnanese, cobalt, and I think zinc - dissolved in probably a petroleum distillate) remains available from elsewhere. The trio is great and I never thought I'd say it, but I'd much rather choose how much drier is in my finish than have the factory put driers in from the start.

Added later 01 min 53 s:

By the way, as a side note - one can cook an asphaltum and linseed oil varnish using gilsonite asphaltum, and it's slow drying, but if something is too big to be cooked, 3% japan drier makes it dry in a couple of days. And it's far tougher and more adhered to metal than any paint I've ever seen. Easier to make as a varnish than any of the natural resin types, and other than stinking when being cooked (like a tire or burning grease), it's pretty easy - doesn't have to get that hot and crosslinks very quickly.