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Tung Oil question (Read 967 times)
 
Turniniton
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Tung Oil question
Feb 24th, 2008 at 2:43pm
 
Hello,
Want to start off saying thank you to everyone who has posted advice to any of my questions over the last couple weeks.  It has been very helpful as I try to learn some of the basics of turning.  Im sure I will have many more questions as I continue:) 
At the moment I have a poplar bowl measuring 11x3 that I am trying to finish.  So far I have applied 4 coats of tung oil, and plan on doing at least a couple more.  Right now when it dries it has a somewhat blotchy appearance to it.  Will that go away with more coats?  In between coats I am lightly sanding with a 1000grit steel wool.  Should I be concerned about the metal shavings damaging the finish at all?  Should I be sanding harder between coats or even mounting on the lathe to sand or polish with a cloth?  Also, on some of bowls after I sand them down I have noticed that I can see very light rings going around the bowl even though the surface is smoothed down to 400 grit.  What is this due to ?
Thanks, Joe
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nuturner
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Re: Tung Oil question
Reply #1 - Feb 24th, 2008 at 11:00pm
 
1.  Will that (blotchy appearance) go away with more coats?
2.  Should I be concerned about the (1000 grit steel wool) metal shavings damaging the finish at all?
3.  Should I be sanding harder between coats or even mounting on the lathe to sand or polish with a cloth?
4.   Also, on some of bowls after I sand them down I have noticed that I can see very light rings going around the bowl even though the surface is smoothed down to 400 grit.  What is this due to ?


I can't speak authoritatively to the blotchy appearance issue, Joe.  My guess would be differences in surface condition (differential in ability of the grain to absorb the oil) which could be caused by a lot of things (including improper sanding) but I can't be certain.
I would recommend staying away from using steel wool at any point in the turning/finishing process.  Those little tiny pieces of steel wool that inevitably catch in the wood fibers can ruin a lot of otherwise very good preparation work.  I'd suggest you throw the steel wool away and stick with other methods of surface preparation prior to and between coats of finish.  A slow turning piece can be surfaced between coats with 1000 grit paper with better results (IMHO) that steel wool could ever provide.
Sanding "harder" makes me wonder if you're allowing the sand paper to do the job or if you're forcing it against the turned piece.  If you're pressing the paper vigorously against the wood you may have identified the answer to your "blotchy" question.  Paper forced against the wood surface creates heat and can heat the surface of the wood enough to damage the pores in the wood, causing the finish to be absorbed unevenly.  This may also be what's causing you to have the "light rings" (scratches) in the wood that aren't always obvious until the finish is applied.
I'd recommend trying to obtain an "off the tool" finish of 150 grit.  That means a 150 grit paper, applied firmly but gently against the turning piece produces an even smooth surface. Then, use your paper grits progressively (150, 180, 220, etc.) until you get to the 600 level (or finer) and NEVER skip a grade of paper between sanding stages.  It's the job of progressive grades of paper to remove the sanding marks (scratches) of the previous grit.  If you skip a grit you will find it difficult (albeit sometimes nearly impossible) to remove the unwanted "rings".
Hope that helps you ...   
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« Last Edit: Feb 24th, 2008 at 11:01pm by N/A »  
 
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Leo Frilot
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Re: Tung Oil question
Reply #2 - Feb 24th, 2008 at 11:37pm
 
Very eloquently put, nuturner.  Especially about pressing hard, if this is the case.  You end up burnishing instead of sanding.  With sanding, heat is your enemy, but is a byproduct as a result of the friction.  You have to be able to control the heat.  Spin slow while sanding is the best recipe.
The problem you seem to be having is one of the primary reasons that I do not like to use stains on turnings, especially oil stains.  But you have a double whammy in this case, oil and POPLAR.  The wood itself is not the best for sanding, IMHO.  I have turned it several times and have sanded through grits with success, but you have to be very observant that you are actually making dust instead of burnishing.  Poplar is a "fuzzy" grained wood and can become a booger in the sanding process.
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Turniniton
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Re: Tung Oil question
Reply #3 - Feb 28th, 2008 at 11:43am
 
Thanks for the responses.  I think a decent portion of my problem was/is in the sanding process.  Probably pressing too hard and sanding at too high of speeds.  Working in the trades for 10 years, sanding was never one of my favorite things and that remains true now!  I have to remind myself that the little bit of taping I did over the years I always had to sand like crazy because I never spent the time to get that skilled at the whole process.  But the guys who taped daily had to sand very little.  I realize as I get better at turning, sharpening my tools, etc.  I will have less sanding to do with each piece I create. 
About the tung oil,  is the idea to put on enough coats to where eventually the last coat(s) will stay on the surface of the piece instead of penetrating into the wood?  I put 8 coats on that poplar bowl with the first 6 drying into the wood.  Should I have stopped there or was I correct in putting on the last 2 coats that seemed to build up on the surface?
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Re: Tung Oil question
Reply #4 - Feb 28th, 2008 at 11:49am
 
Either.  Some will stop as they see the beginnings of a build, that splotchy shine look.  You can then buff to a pretty uniform shine.  Others will continue until they have a uniform shine, maybe even add one more coat, before buffing if they buff at all.  It's one of those deals where you really have to experiment to find the finish you like best.
CoolRev. Doug Miller
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Re: Tung Oil question
Reply #5 - Mar 14th, 2008 at 10:37am
 
I have put MANY coats of tung oil on projects and find I can use General Finishes brand Arm-r-gel satin, in place of tung or danish type oils, and get done with WAY fewer coats, better protection and same look. I find even though it says satin that I can get it up to semi with 3-4 coats. It's easy too.
That's just how I do it for satin to semi-gloss. When I want gloss I use Minwax wipe on poly. I have tried many others and this is the easiest, best overall for me.
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Re: Tung Oil question
Reply #6 - Mar 14th, 2008 at 6:18pm
 
Criag, you are right, the Arm-R-Gel will build faster.  The big difference is that the Arm-R-Gel is a surface finish.  Meaning that it doesn't soak into the wood per se.  It may soak in about 1/32", but not much more than that.  Your oil finish, on the other hand, will soak into the wood until the pores of the wood are filled.  In other words, it goes through and through.  That is why it takes more coats than the varnish/surface finishes.  A lot of folks are applying one or two coats of oil followed by a product like this one or even Seal-A-Cell from the same company.  Then they follow up with a good buffing once the finish is cured. 

Everyone has their favorite.  The beauty is that is matters not what your favorite is.  They all work and do what they are meant to do.  So, we have to decide what the end use will be and adjust our final finish accordingly (what ever that means  Undecided). 
CoolRev. Doug Miller
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