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Finish for "rotten" wood?

C

Charlie Harley

Joined
Jun 20, 2006
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Location
Cincinnati, OH
Hi everybody. I've been lurking on your site for a while and finally decided to jump in and post.

What is a good way to finish "rotten" wood?

I found an interesting piece of crotch wood on my folks' farm. It was from an oak tree that was lightning struck about ten years ago. About 2/3 of the piece was weathered but still solid. The other 1/3 was eaten by bugs and partially rotten. The pattern intrigued me.

I cleaned the wood with bug spray, a stiff brush, and compressed air. What was left was interesting and fairly solid, but parts are still fragile.

I turned it to a neat shape. Now it's time to apply a finish.

What do you all suggest?

I thought of using a spray on finish to get down into all the surfaces.

What about a dip finish? Does such a thing exist?

I thought of rubbing oil on only the exterior turned/sanded surfaces and leaving the interior in its natural state.

So what do you all suggest? Any help is much appreciated.

P.S. As to my background, I'm an experienced cabinet maker but new to turning. Working with this "rotten" wood is completely new to me.
 
Welcome, Charlie!

On the matter of the wood---is it punky (soft), or just spalted (figured from decay yet still firm)? From what I have read, punky wood can be stabilized with cyanoacrylate glue (CA glue, or superglue).

If, however, you've managed to successfully turn the wood, I would imagine that it wasn't very punky. The finish you put on it is up to you, however I would opine that your idea of a spray finish is a good one. If the wood is firm enough to withstand it, and the shape conducive, you may want to consider a rubbed/buffed finish, applied on the lathe. I've seen dipped finishes used at the Louisville Slugger factory, but would not recommend them. Dipped surface coatings will invariably drip off, causing uneven areas in the finish, and dipped penetrating finishes will still require some rubbing and/or wiping.

Remeber also that with anything turned, you will invariably be sanding against the grain at some point or another. Thus, sanding marks will be very visible, possibly up to as high as 320 grit. I usually sand to 600, however have heard of other turners who sand up to 1200. By the time you get to these fine grits, the wood is becoming less sanded and more polished/burnished.

Good luck!
 
I have found that I like to use penetrating finishes such as Watco Danish oil for some of these softer woods. It will darken the wood though. But they soak in and harden the material to a certain extent. You don’t have to worry about rubbing it in if you put it on heavy enough. It is more a matter of wiping it off. My method is to drench the material and keep it wet for 10-15 minutes. Then start wiping it off. I use a dry rag and switch once it is saturated. I continue this until the surface stops bleeding. I then leave the piece to dry and keep an eye on it over the next couple hours because there may be a little more finish that bleeds up to the surface. If you don’t wipe it as it bleeds up it leave little shinny spots that are tough to buff off.

If you want a higher gloss finish, you can put another surface treatment over this type of oil finish after it has cured well for a week or so. This second finish will apply more uniformly because the oil has sealed the surface below. It still may require a couple coats though.

I usually sand to at least 400. Sometime I wet sand to 600 using Watco as the lubricant. This process seals and polishes at the same time. After it has dried I’ll buff the piece with EEE and white diamond compounds.
 
I'm a fan of the soak-wipe-dry-sand-soak approach meself. I use danish or eurythane oil. I find that the punky part will absorb more and more over time until it is basically plasticized. On the final coat, wipe very lightly and it will dry with a nice gloss.

Now it will, as said, leave the wood with a wet look. I generally like this but, if you don't, use a water based eurythane finish. This will dry with a "dry" look to it. Same process past that.

Dietrich
 
High-solids surface finish is probably the best. Full-strength poly or lacquer. Problem with penetrating finishes is in getting any kind of an even look. They sink into the punky stuff and shine on the firm.

You might try a sort of a mixed finishing schedule based on shellac. With dry wood the solvent alcohol will snuggle up pretty well to the cellulose and carry the resin in well. 2# cut, not just a sanding sealer. Then scuff to provide a mechanical bond for the urethane or whatever you choose. Better than trying to soak an oil finish in and suffering through curing problems. The boiling point of ethanol is low enough to give you a good rapid dry.
 
Wood treat

You may consider "POLYCRYL" made by the same outfit as "PENTACRYL". I have used both with very good results. They are available at you local Woodcraft or Rockler stores, of thru Craft Supplies mail order out of Utah.
 
What is "poly"?

I agree that a penetrating finish would get very uneven given the differences in wood densities of this piece. It is not "punky", but there are parts which are very porous and parts that have naturally dried to a rock hard state.

It was an interesting challenge to turn the piece. Sharp tools and lots of patience.
 
Charlie Harley said:
What is "poly"?
Click to expand...

You're kidding, right? Though it's just a prefix, most folks understand it to be polyurethane resin carried by some solvent.

There are some pieces which can't, and possibly shouldn't be saved. For instance the one below, which features a lump of mush made by squeezing the water out of some stuff that used to fill the hole it's sitting in. It even reeked of stagnant water.
 

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Charlie, be sure to post some pictures at some point. I am also a former cabinet/furniture myself and fairly new to turning myself (about 3 years, give or take a few spins). It is still amazing to me what other woodworkers would never even look at due to bad "rot" but woodturners will fight over it! Go figure!

Personally I have used various laquer based sanding sealers to give some strength to soft woods (punky, rotten, spalted, etc.) so I could turn them. If the wood is dry the sanding sealer soaks in pretty good and dries fast. I have also used tung oil, which soaks in good but takes a while to really harden. I typically finish bowls with tung oil or walnut oil so I use tung oil if it will have an oil finish, if it is going to get a lacquer finish I use sanding sealer.
 
I'm a fan of thinned lacquer for stabilizing punky wood. It will actually penetrate all the way through the wood and once it hardens will work nicely. It will clog sandpaper however so cut cleanly and shear scrape if necessary to clean up the tool marks. I also willuse a card scraper with the lathe off to get really bad areas of tearout although the lacquer will often firm up the wood so you don't have any tearout.
 
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