Hello All,
I have made a smallish table with a top made out of a maple log I rolled around in the yard for a year to promote some spalting. When I opened up the log, it might as well have been a pirates treasure chest! Beautiful black-line spalting! After waiting 2+ years for further air-drying, I finally chose two pieces for the top. Jointed them. Let them rest (6 mo.) Re-jointed, cut to fit, ready to finish, but can’t seem to get a consistent sheen. I used a wood stabilizer to strengthen the punky areas, but the finish ( Tung oil ) doesn’t look good. Dry spots and shiny areas jump out. Should I put on a top coat, like a 2lb cut of shellac or a thinned poly? This is one of the coolest tables I have ever made and don’t want to roast marshmallows over its burning embers. Help!
Regards, Sean
Replies
Uneven absorption of finish is a common problem with spalted wood. I don't think you'll lose your table to firewood, but it'll be interesting to see what people come up with. We don't seem to have many members who actually work with spalted wood here, or maybe they just haven't been around much lately.
Do you have any spare wood you can experiment with? I'd be tempted to start with shellac until a uniform surface came into being.
Sean,
I once made a kitchen table and a matching trolley using spalted sycamore for the former and spalted beech for the latter. The beech seemed to have a lot of punk in it (the sycamore had none).
Not knowing a better way, I ended up pouring rather a lot of Tung oil into the beech. The punky stuff just drank it but after I don't know how many applications, it eventually built a sheen. It takes time, as pure Tung oil does not dry fast.
The owner was gven a full bottle of Tung oil and told to keep applying it if and when the punky areas got dull. He did have to make another application or two but the last time I looked the surfaces seemed fine. The trolley gets wiped quite often, it being a kitchen implement, and I suspect this might help keep it's sheen.
I suspect also that all that oil might tend to keep the wood more stable, even in a steamy kitchen (but that's a guess).
Lataxe
You don't say what kind of tung oil you are using, though if there are shiny spots, it sounds as if it might be something like Formby's. If so, it may really be just a wiping varnish, and probably much better for your application than if it were pure tung oil. The varnish will cure harder than the oil, and can be allowed, eventually to build a thin film on the surface. I think that if you want some sort of sheen that you continue with a wiping varnish--sanding between coats using 320 grit paper on a sanding block to keep the built up on the denser parts from building up too much. It will still require quite a few coats for the punky parts to stop absorbing more finish. But, eventually you will get there if you are patient. Remember it takes 3 coats of wiping varnish to lay down the equivalent of one coat of brushed on full strength varnish. If you want a satin finish in the end, you can make the last couple of coats with a satin wiping varnish.
Pure tung oil, even on unspalted woods requires 5 or more coats, with sanding between each to develop a low satin finish. With pure tung oil you need to be sure all excess is wiped off since any remaining on the surface would be soft. On spalted wood it could be many many more coats to achieve an even sheen but it would still leave punky areas soft.
I've just recently worked with some spalted big leaf maple. I can vouch for the shellac approach. I used Zinser Clear (Blond) right out of the can and loaded it up heavy into the punky areas. Works very well!!
I tried BLO on a sample and was not happy at all. It turned the wood too dark. Try the shellac on a sample; I think you'll like it.
No bon fire! LOL
Mack
"WISH IN ONE HAND, S--T IN THE OTHER AND SEE WHICH FILLS UP FIRST"
Edited 6/12/2008 10:06 am ET by Mackwood
I have used coats numbering into the thirties on some spalted pieces (polyurethanes). I would definitely NOT use shellac as it becomes brittle in thicker applications (which you need here). To make it truly nice you must keep the finish thin over the main surface while sating the thirst of the spongey areas. This means that you must sand between coats to limit the build on the less thirsty areas. Today I'd probably use something like Kwik Poly to speed the filling process but many (easy to apply) coats of polyurethanes is still a good strategy.
It takes perseverance to deal with this difficult material in the way of excellence that it seems deserving of. I once read an interview of a fly tyer who was questioned by a visitor at one of his exhibitions. The visitor was an aspiring tyer himself and asked about the varnish used for the glossy heads on the exhibitor's flies. The exhibitor (knowing that his varnish was ordinary stuff) asked the visitor how many coats he was using and was answered "two or three". "Well there's your problem" he told the visitor. "The flies you see here have from thirty-two to fourty-six coats of varnish on their heads." The visitor left angry that the selfish exhibitor wouldn't share his secret varnish formula. Of course he had the truth told to him straight out and refused the answer because he did not believe that anyone would do that much work, even for the stunning results that he saw. There is a moral in this story for spalted wood finishers... can you see it?
Link to Kwik Poly: http://kwikpolyllc.com/
The punky areas will soak up the first couple of coats with no brittleness problem. They could even be coated separately at the beginning.
The boxes I made and finished with shellac have five coats of shellac scuffed between coats with 220, 320, 000 Steel wool and 0000 Steel wool. Final finish was one coat of Maloof finish part 2 followed by a very light coat of Briwax. They have a nice mellow sheen and are very pleasant to handle.
The punky areas obviously finished at a different rate than the rest but turned out quite even.
Regards,
Mack"Close enough for government work=measured with a micrometer, marked with chalk and cut with an axe"
Thanks all for the input. I applied another coat of that crappy Formbys tung oil finish, (it's miles from real tung oil, but it has a longer shelf life I guess)and it seems to be working towards a consistent sheen. No more than twenty or so applications will be needed. LOL. Also, thanks for saving me from slathering a bunch of shellac on it, you guys are great.
Best Regards,
Sean
Formby's Varnish sold as Tung Oil Finish isn't a bad product, the only thing I have against Formby's is the marketing that leaves users confused about what they are using.
Sean, once this adventure is complete and you've had time to recover, you might want to pick up a couple of finishing books (Flexner, Jewitt for examples) and read about these tung-oil finishes, and recipes for making your own blends. Formby et al., make way too much money off of the stuff they market under (practically) false pretenses.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Good advice Girl. I sometimes neglect to think through the finishing during the planning stages of a project. It's way to important to take lightly. Thanks . Sean
Here's one more solution: Minwax Wood Hardener. This product is specifically sold for hardening partially rotten wood and works wonderfully to harden it up so that you can machine it or finish it. I'm not totally sure of its composition, but I suspect it has a fair amount of an epoxy monomer in it.
I'm not sure of its compatibility with tung oil or oil/varnish blends. It's intended to soak into the wood, so it's probably a solution best used for other parts of your spalted wood stash when you make other projects out of it.
I used a wood stabilizer before the final jointing. It took much of the sponginess out, however, the tung oil still poured into it like a sponge. I have continued to apply more coats, and it is beginning to find a balance in its sheen. Thanks for all of the input.
Regards,
Sean
I know that in the case of your large table top this is impractical: but if you have small pieces of spalted wood with punky areas, such as a jewlery box lid, the thin cyanoacrylate glues, super glue, do an admirable job of stiffening up the punky spots. It is applied liberally, really pour it on, to the soft areas, and often it will require more than one coat, and when it is dry, several hours, sand the surface smooth using a sanding block. After a film finish is applied the soft areas will have the same look as the harder areas. This works great on smaller pieces but on something as large as a table top it could get expensive!
Bruce
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