Odd behavior with General F Arm-R-Seal: rippling, shriveling, veins in finish

[John W Henderson]

I've been working on a cribbage board for a nightmarish amount of time. The board itself was cake -- it's the finish that's got me on the verge of... well, unpleasant things. I found my old General Finishes to have gone bad, and I tried to make it work, such as with THIS THREAD (http://www.sawmillcreek.org/showthread.php?172596-Thinning-General-Arm-R-Seal-urethane-topcoat-that-might-have-dried-out-a-bit&highlight=).

In any case, I went out and got a brand new can of General Finishes Arm-R-Seal Oil & Poly semi-gloss. I built up a few coats and was pretty happy with it, but in my a-retentiveness, I burned through to wood when trying to wet sand out some piece of dust or lint that I could see. Bummer. I re-scuffed the whole thing and started again. To combat dust, I started applying the finish and then putting a cardboard box over the top of my board. This worked really well to keep dust from the air off the board.

On my third coat of this... all of the sudden I got radical "veins" running all through my board. It looked like the liquid had "shriveled" up and left these monstrous protruding veins coursing around. The sides looked more like runs -- like they "sagged."

I figured that it was due to my cardboard box. I thought that without air circulation, perhaps the drying time had increased and caused something funny to happen without direct exposure to plenty of air. Who knows, though?

I tried to sand all of these flat, but it was just too much. I ended up burning through in a couple places and so I started over... again. Now I took to putting the board in the bathtub on some 1x1 slats and drawing the curtain closed. This also worked really well for dust. Well, I just did the second coat and already those veins are back!

I have no idea what would cause this!! Here are some pictures. I put black dots just below anywhere there's veins, as I have to take a picture in just the right light to capture them:

210277 210278 210279

The last one looks more like spots/orange peel than running veins like the other two.

Any thoughts on this? Feel free to ask for more information.


Thanks,
John

PS. I apply the finish with a folded cotton t-shirt rag. Same as I do with other things. I've used this finish on many other boards and never had this happen. I'm going to sand this one down and re-apply, leaving it in the room I always use rather than the bathroom. I'll deal with the dust somehow -- not getting finish on flat is a bigger problem than dust. I'll post back in a couple days with the results.

[Howard Acheson]

Some questions:

What is the species of wood?
How are you applying the finish?
When you say "wet sand" what are the details? Grit and process? What kind of backer are you using for the sand paper? How long are you letting the finish dry before wet sanding?

Urethane varnishes are not the best candidates for wet sanding. Urethane is added to varnish to make it more resistant to scratching. Wet sanding is scratching and it's difficult to end up with a consistent scratch pattern. To have the best chance at rubbing out, the finish should be allowed to fully cure for 3-4 weeks.
Urethane varnishes will never be any better than they are right out of the can. Another point about the finish, Arm R Seal is a fairly highly thinned product. If you plan to wet sand, you should build up at least 5-6 coats to have enough film thickness so that sand through chances are minimized.

Finally, just a quick observation. It looks like your "veins" may be just the hard annual grain structure. Some woods that have prominent grain figure have both soft wood created by summer growth and hard darker wood created by winter growth. When sanding, the sandpaper will more easily and quickly remove the softer wood between the hard wood. This makes the hard wood lines in the finish. They will actually be raised areas because that do not get sand down. The more you sand, the more prominent the lines both in looks and feel. It would also explain why the first coats seemed to sand smoothly but the lines started to become prominent as you continued the process.

[John W Henderson]

@Howie: thanks for the response. To your questions:

- My process: dip 600 grit 3M wet or dry in water, spread water with my hand on the wood, and sand with my hand as the backer

- The wood is maple with inlaid brazillian cherry

- I apply the finish with a folded up piece of old white, cotton t-shirt

- Good tip on allowing it to dry sufficiently. That may contribute, though I would expect this to just not allow good "rubbing out," not the veins

- I was tempted to say that the veins are aligned with grans, but the veins look to be the same (random, same approx. spacing, same thickness) in both species of wood and they have insanely different grain patterns. It also doesn't explain why one side of the board has long thin veins while the other has more of an orange peel/dimpled pattern

- The veins are there upon drying; they don't become any more prominent as I sand. I have a hard time imagining that *that much* protrusion would build on the finish when I can't see such things during initial coats. Oh, I should take a picture of the sides, as those are vertical when drying and they end up looking like they've sagged/run, not veins. Thus, I think something weird is happening with the finish chemically or due to the air properties, not the wood.

I could be wrong, though!

[ray hampton]

Do you think if you apply the finish then hung the board upside down to dry that the dust will not settle on it ?

[John TenEyck]

If you are getting dust nibs in Arm-R-Seal then either your room is VERY dusty or you are putting on far too thick a layer. Arm-R-Seal is meant to be wiped on and wiped nearly off. It's a close to the wood finish. Your comment about seeing sags in the finish on the sides suggests to me that you are applying too heavy a coat. I would not choose it if/when your objective is to build up a film thick enough that you can wet sand it. 3 or 4 thin coats is all I ever use, I almost never get dust nibs even though I apply it in my shop, and any dust nibs I do get are easily removed after a week or so with a brown paper bag.

[Howard Acheson]

wet sanding a flat surface with your hand or fingers as a backer may be contributing to your problem. One of the prime objectives of wet sanding is to flatten the finish. Using your hand or some other non-rigid backer method will allow your sanding to move up and down with the unevenness of the finish. It will cause you to remove more of the soft between winter grain. For flat sanding, mount your sandpaper on a felt covered wood block or a hard rubber sanding block. The rigid surface will level both the hard and soft portions of the wood equally. For the same reason, using a flexible non-woven abrasive like Scotchbrite or steel wool will not flatten a surface.

[John Coloccia]

FWIW, I've found the best sanding "block" for leveling a finish to be an eraser. Just your run of the mill, rectangular eraser wrapped with sandpaper.

[John W Henderson]

@rayhampton: yes, that's an idea I had not thought of. I would have to do the top separately from the sides, I think, though. I'd clamp on the sides and suspend the clamps from a horizontal rod or something like that. Good suggestion.

@John TenEyck: I'd agree with the thick coat thing, except that I'm not doing this any different, that I know of, compared to a bunch of other boards and a picture frame I used the same stuff on. I use a t-shirt and usually do a set of final passes to even everything out... how thick of a coating can a folded t-shirt used in that manner leave behind? I'd say it's very thin. I'm not really trying to "wet sand" in the sense of progressing through up to 2000 and then pumicing or something. I just wet sand to get dust nibs out. I hadn't heard of the brown bag trick.

---

To the rest: the veins are there when the material dries. As far as I know, it shouldn't have anything to do with wet sanding, should it? I just lightly go over the surface to get out any issues from the previous coat, and I dry often to re-check the nibs I'm focusing on. I only wet sand because I've tried dry-sanding those areas and they burn through much faster. I'm thinking of using 80 to just start all over on fresh wood. I just thought someone might have seen this before. It's truly baffling to me. I appreciate the suggestions, but would it fair to say that the answer, so far, is, "No, I have never seen anything like that"?

[John W Henderson]

@John TenEyck: I sanded down and am now applying in extremely thin coats. I'm wondering if that was the problem. I checked things after only a couple hours and they were already quite dry. Maybe I was being too liberal with the instructions' recommendation of "thin to moderate" coats. I put this coat on like I'd be applying oil or wax polish, just attempting to dampen/wet the surface and no more. Thanks for the tip; things are looking much better already. This probably explains why I thought I had enough to wet sand (I was applying a lot more than one would suspect) and that seemed odd to others. Thanks.

[John TenEyck]

John, happy to hear your results have improved. I think you'll find that as you build 3 or 4 thin coats of Arm-R-Seal all you'll need between coats is a light scuff sanding with (dry) 320 or 400 grit. You can put the first coat on heavy, keep the surface wet for several minutes until it stops absorbing, then wipe it off to leave a very thin almost dry layer. Let that coat dry/cure at least 24 hours - it takes longer than the subsequent coats because it's in the wood and not just on the surface. The subsequent coats will cure more quickly, usually in less than 12 hours. All the coats should be dust free almost immediately and certainly within a few minutes. If not, something's wrong and most likely because it's too thick.

John

[Harvey Pascoe]

I have had that happen on occasion and I have no idea what causes it. To remedy all I did was sand it down and recoat. Presto! Problem gone. Could be caused by stearated sandpaper.