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It looks like I have an interesting experiment on my hands (below).  The right side of the back rail has had tung oil applied, and apparently the back rail received a few drops as well.  The "splotchiness" of the finish has been an unfortunate surprise.   I've been reading logs regarding tung oil; it appears that some people apply directly to the model at 100% strength, whereas others apply a 50/50 mixture of tung and mineral spirits.  I suspect now that I should have applied a 50/50 mixture to avoid splotchiness.  Thoughts?  I've also heard that "more is better", and that splotchiness can be overcome with more coats.  I can go that route, or apply mineral spirits now to remove what has been done to date.  Thoughts?  I'm not sure how to proceed.  

 

The frustrating thing is that I tested the tung oil at 100% strength on identically sanded samples, and none of them revealed the splotchiness effect.  Just this rail.  The sides also look acceptable with just the "shiyiness" aspect to address....

 

Alan

 

766098420_IMGP1681-800.jpg.bcbbe67b492c34935a3d0a2938b58aec.jpg

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My observations re: pure ting oil, not tung  oil “finish,” on new walnut rifle stocks.  First couple of coats cut 50:50 with mineral spirits.  Applied liberally and allowed to soak in for about 20 minutes or so, then excess buffed off.  Wait about a day between applications.  Later coats, maybe 10 or more for long-term protection, cut about 75:25 tung to mineral spirits.  Buff well with a cotton tee shirt in between.applications.  Makes for a nice deep, water proof (or resistant) finish.  Note that with age the tung oil oxidizes to a nice reddish brown color.

 

Not sure this directly addresses your post, but maybe cutting the tung more will help even out the splotches.

 

HTH,

 

Keith

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Guys; for years I've used tung oil for finishing furniture. I've always gotten great finishes on hardwood but lately I've encountered problems especially using it on small parts. I'm probably doing something wrong but it seems to "raise the grain" on all types of wood. Any thoughts?...Moab

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Excellent feedback.  Thank you!  I'll fiddle with what I've already done, then thin the oil with mineral spirits, and proceed according to the above instruction.

 

Mark, no danger of glue spots on this one.  I'd sanded the rails down with progressively finer grits until the last phase, which was done with a grit almost as fine as paper.  I do wonder if the surface was "too" smooth, not allowing the oil to penetrate properly...

 

Alan

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Moab,

regarding the raised grain, did you acclimate the wood before applying the tung oil?  Also conditioning with a diluted oil, let the piece sit, sand and reapply helps.  However, like you, my experience with tung oil is with furniture. 

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Just a possibly redundant safety note: Real tung oil (Which should be clearly disclosed on the container, rather than "tung oil finish," which can be darn near anything, is basically "Chinese linseed oil." "Linseed oil" is also known as and sold as "flax seed oil," often in health food stores (and for a lot less than "raw linseed oil" in paint stores.)  Tung oil, a common component of varnish, like linseed oil, once a common component of paint, when "drying," or "curing," can cause oil-soaked rags to spontaneously combust. Everybody seemed to know this in the days before water-based coatings became popular. I've had younger people look skeptical when this is explained to them. Back in the day, a lot of shop fires were caused by oily paint rags left lying around or just tossed in the trash can.

 

All rags and other material containing tung, and linseed oil, or any wet solvent, should be carefully disposed of by hanging outside spread in the cooling open air away from where fire might spread and cause damage, or better yet, submerged in a water-filled covered metal container and left to "cure" in the water before final disposal.  An oily rag or paper towel balled up and tossed aside can burst into flames without warning long after you've left the shop.

 

A bit "preachy," I know, but it doesn't seem to be common knowledge to the extent it used to be.

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Bob,

 

I'd heard that as well.   I'm using Formby's.  I'm not at home right now, but I'm pretty sure it isn't real tung oil.  I have to admit I'd wondered if my model would spontaneously combust or not. :)

 

Alan

Edited by knightyo

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The polymerization reaction of the oil is exothermic - the oil exposed to oxygen generates heat.  On a flat open surface, the relatively low heat dissipates quickly.  A ball of rags in a closed space, can retain enough of the generated heat at a central point to cause the combination of air, oil, solvent, and cellulose to generate a chain reaction without a spark.  The trick is making sure that the heat dissipates in a room temp environment.

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When my house was under construction 30-ish years ago, the painters used tung oil as the finish on my windows.  The rags were left in a pile and spontaneously combusted, burning a large hole in my bedroom floor.  I was lucky the whole place didn't go up in smoke.

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For the record: tung oil and linseed oil are highly unsubstituted vegetable oils. They "dry" through oxidation. Oxidation is exothermic and thus the fire potential if stuffed in a ball without proper ventilation. Used engine oil will not ignite from oxidation because it has already been thoroughly oxidized in your crankcase. Solvent soaked rags are not heat generating but if the room temperature exceeds the flash point of the solvent and a spark source is nearby fire will result. Keep rags with drying oils and solvents away from your home

Jaxboat

Edited by Jaxboat

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For years I used "tung oil" on the furniture I made.  I got very good results by applying it full strength, waiting about 30 minutes and then wiping it off thoroughly.  The next day I'd buff the whole piece with 0000 steel wool and slather on another coat.  Wait, wipe off and let dry.  The next day, same thing.  After three applications the finish was terrific and that was it.  Rags went into an outdoor trash can and were carted off weekly by our local trash picker-uppers.  Ultimately I stopped using "tung oil" because (a) it took so long to apply, (b) it was not very water resistant and (c) I discovered the beauties of Sherwin-Williams water resistant spraying lacquer.  I could spray three coats, buffing between each coat with the 0000 steel wool, and have a fine (and durable) semi-gloss finish by day's end.  Spraying lacquer on ship models ain't so easy, so I use Deft brushing lacquer or a water-based polyurethane and rub it to a nice semi-gloss final finish with the aforementioned 0000 steel wool.  Good ventilation required in all cases.  

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