Sapele finish problem

Having some strange problems with Sapele finish. It seems to suck up the finish and become raw wood again.
Did Tung oil first and let dry 48 hrs
Applied a few thinned coats of dewaxed shellac.
Applied Briwax using a synthetic scrub pad and it buffed out to a beautiful flat finish.
A few days later I had severe "dry spots". It looks like I scrubbed through the finish and have raw wood on about 75% of the surface. I did another sample with more coats of shellac and a few days later same thing. I thought for sure too much scrubbing even though I did a very light job.
But now I find one of my first samples that I never waxed and it has done the same thing. It's like the wood sucked up the shellac and dried out. In fact the new find seemingly has raised grain.
I've heard this wood can be a problem but kind of baffled but intrigued too. Really glad I didn't sell the first article before I saw this problem, it takes a few days to appear.
Any thoughts?
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One of the reasons I quit using an oil for a finish and or prefinish. I learned that a varnish will typically not do that but it does take 2 or 3 coats before it stops looking dry. I have not worked with Sapele but have worked with many other woods that do what you describe.
At a local lumber dealer one of the salesmen had a chunk of exotic wood setting on his desk. He ad been applying Watco oil, it looked great. How many coats did you apply, I asked. He answered, lost count after 30.
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Yeah, I wasn't looking for build, just using the oil to add some depth. The Sapele has some nice sparkle when oiled. I love the look of a built up oil finish but just too much trouble to maintain and not protective enough.

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On Fri, 13 Nov 2009 09:43:19 -0800 (PST), the infamous

Then you'll love Waterlox. See other post.
-- You know, in about 40 years, we'll have literally thousands of OLD LADIES running around with TATTOOS, and Rap Music will be the Golden Oldies. Now that's SCARY! --Maxine
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It's a pretty popular sub/replacement for Honduras mahogany with instrument builders. Maybe you could check with a few of them... or maybe at rec.music.makers.builders
Ed

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SonomaProducts.com wrote:

I've never used it and a _very_ quick search didn't uncover anything particularly useful.
So, no known answer but--have you tried a sanding sealer to see if will help?
I didn't go look to see if could find anything at US Forest Products Lab site, though...
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SP - tung oil takes about 10 days to dry, but about 21 (more if applied fairly heavily) to cure out. You know the drill, depending on how humid it is, how hot it is, etc. Since tung has little or no drier in it (compared to BLO) it dries at its own speed.
I am thinking that the tung is your problem. The uncured oil spoiled your finish by trying to outgas under your shellac. Even shellac can't bridge over larger areas of oil, say bigger than a carpenter's pencil sized dot because the two products are not miscible. The alcohol/shellac will simply sit on the oil, and not bite in. Although it bridged at first, you can see the deterioration.
I had this happen years ago when I started refinishing, and incorrectly diagnosed the problem as a contaminated surface. I guess in a way it was, but that wasn't the culprit. It was incorrect procedure. Unfortunately, I repeated the procedure a couple of times before I found out it was me, not the materials, not the applicators, not the wood, and not the procedure.
Oils of any kind over tropicals can be problematic. The grain patterns on some can be very dense and then less than that without changing much in appearance. With that in mind you can see how that would affect the amount of oil that would be absorbed into the wood, as well as how quickly it was absorbed.
Although I appreciate the beauty of real oil finishes, since they provide very little protection to wood, I don't use them myself. I don't like the inconsistency when using them as a finishing protocol. I like predictability, and with so many other high quality resin finishes out there that mimic the appearance of oil but have a more repeatable outcome, oil is off the list.
As a suggestion for the fix, you might be in a bit of a pickle. The wax will leave behinds silicones, oils, bee's wax and carnauba residue. Your efforts to refinish will be hampered unless you get off the wax entirely, so in my opinion that means a stripping.
If you try to simply sand it off, the heat from sanding and the swirling motion of the sander will simply grind the above mentioned components into the wood, and compound the problem. When you apply your top coat, you will have similar results as you have now, but from a different source.
Personally, I never, ever, put wax on anything. Thinking of refinishing or finish repair, it makes it significantly harder to do.
Strip it, clean it down with a lacquer thinner bath and start again.
Good luck!
As always, just my 0.02.
Robert
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Thanks. I was suspecting the oil as the problem but I really like the depth it adds t the wood. The Sapele is very porus and soaked it up well. Maybe I'll try going with a BLO job.
No problem on ruining the project. Yes, this one is too far gone to fix. I might try slathering a few coats of wax and see if I can get enough build for it to last.
I cut parts for 4 of these, all as prototypes for my (pending) kit business. This was the fist offiical kit I am preparing. Just got the Sapele on a deal so tried it out. I do want to provide a recommended finish technique (that works). So I have 3 more tries wih the parts on hand.
I'll be taking videos and pictures during assembly and finsh of next one or two to use as assmebly instructions.
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I used polyurethane on Sapelle and it finished beautifully. Probably not the look you're after, but it does work. If I were to try and pop the grain, I'd use an oil/varnish mix that provides a harder/firmer base than just oil.. My only excuse is brainwashing by shop instructors who claim oil alone as base coat is too soft. But what do they know or I .. Good luck with your next try..

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SonomaProducts.com wrote:

I dunno...what particular oil product did you use? Most of the tung oil preparations do have driers; in general doesn't one have to look specifically for a product that doesn't? I've generally used the ol' "tried 'n true" Minwax Antique Oil since I started w/ it 30+ years ago when didn't know anything at all and have never been particularly dissatisfied so I just keep on keepin' on... :)
As said, I've not had any to actually work on, but sounds to me more like the issue of porosity than the finish not actually curing.
The surface prep w/ the sealer or a cut shellac first instead of later would seem to me certainly worth a try...
But, of course, that's all un-swag speculation... :)
--
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100% pure Tung thinned with mineral spirits.

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Oops, actually did buy real Turp for thinning.

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SonomaProducts.com wrote:

Well, in that case, possibly...there's another one I've never done because was always told it would be long time to dry (as in good approximation to "forever"... :) ).
--
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If you used tung oil from Woodcraft, it has NO driers. You will be waiting.
BLO has metallic driers, but it dries slowly and still takes a while to cure out. You can finish with another oil topcoat on top of BLO, but you should still wait about 14 - 21 days. Since I do production finishing, I don't use BLO except when making one of my witch's brews.
I passed this forumula on to BARRY a couple of years back, and he loved it. BARRY (now only found on Lumberjocks) did a lot of professional finishing for different builders in his area. Like me (and like you!) he was always looking for an edge in speed and appearance.
It was modified by me, and it works just as well as the original formula that was passed to me by another finisher. You can go over this in a couple of hours and it makes a great undercoat/conditioner. Multiple coats of this stuff in a day are easy. Keep it stirred up.
A couple of coats of wipe on poly/varnish/shellac over this is fast and makes the end product look like million bucks.
http://www.bburke.com/woodworking/robertsformulaphotos.html
Note that you should use pure gum turpentine (not paint thinner or anything BUT pure gum), and dewaxed shellac (sanding sealer).

Well, that's got to be a relief!

So what are you making?
Inquiring minds you know....
:^)
Robert
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Yeah I have played with an oil\turp\shellac mix in the past but felt like after the first coat the oil was just sitting on the shellac so never adopted it.
I am making a little clock I showed here once before. My own design, Stcklyish, called "Little Gus".
http://www.sonomaproducts.com/images/My-clock.jpg
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I like it! It looks strangely traditional and stylish all at once. The clock face is a perfect match for the style. Nice job, great design! Robert
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On Fri, 13 Nov 2009 09:41:39 -0800 (PST), the infamous

Try using some Waterlox on the next one. But give it time to soak in this time, then give it plenty time to dry before waxing if you do.
Highly figured Sapele and burls can have lots of end grain exposed, hence the soakup problem. Keep adding finish and allow it to soak in until it doesn't do that any more. Yes, this will take weeks or months. Just do it.
-- You know, in about 40 years, we'll have literally thousands of OLD LADIES running around with TATTOOS, and Rap Music will be the Golden Oldies. Now that's SCARY! --Maxine
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