PLEASE, I need help: Oil based poly, terrible finish, no idea why.

[Old Greenhorn]

I am going nuts here. I have a slab table top I am finishing for a client. It's maple, dried about 3 years or more. I did all the same things I have done on a dozen other tables, but for some reason the finish on this is coming out like crap, even as I put it on. The only difference is I did not put on tung oil or anything else before the poly. The client wanted it as clean as possible. The one other difference is that the client wanted semi-gloss and I have always used gloss. I did purchase the same brand of poly (Verathane). I have put on a coat, sanded after, done another, it gets no better. 
 The issue is that I get all these tiny bubbles like dust dots and it is extremely streaky. When it dries it looks just as bad or worse. I have resanded to clean wood a couple of times now, or tried sanding just to take out the flaws. Neither changes things. I tried wiping clean with mineral spirits, letting it dry, then applying the finish, same result. I tried putting stain sealer on before applying the finish, same result. It's hard to get photos of this, but if you look at this one close, I think you can see it.


 

I am beginning to wonder if I have a bad can of poly. It is a little more cloudy than I recall it being in the past, but that could be my imagination. I am using chip 2" brushes to apply it, but I have always used those. I have no idea what is causing all those dots that look like acne. The shop is at about 68-72° throughout the day, but the humidity might be a little higher than normal. I have only been heating for a few days now. Still, I feel like I am missing something basic. I did try a different piece of wood, freshly planed, joined, and sanded today of Birch, and that is even worse. 
 I am at my wits end. Any help would be appreciated greatly.

[beav]

Looks to me like outgassing. I used to get it when building west system (epoxy encapsulated) boats.
The temperature of the piece and the shop should slowly decrease after application of first coat so the wood sucks it in instead of bubbling air out as it dries or hardens warming up and expanding.
Clear as mud?

[Southside]

@Poquo any ideas?

[Old Greenhorn]

Looks to me like outgassing. I used to get it when building west system (epoxy encapsulated) boats.
The temperature of the piece and the shop should slowly decrease after application of first coat so the wood sucks it in instead of bubbling air out as it dries or hardens warming up and expanding.
Clear as mud?

Yeah, I thought that too, but that's why I did a test sanding all the way to bare wood, then applying a stain sealer before putting on another coat. same result. Also, those things that look like 'bubbles' may be some kind of contamination. There is no evidence I would expect to see from outgassing, such as the occasional bubble that does not burst, which is why I am wondering if I got a bad (old) can of finish. Put another way, I wonder if the problem is in the finish itself. Anybody ever get a bad can? I had a similar problem when I used to buy half gallons and used them over too long a period, the stuff would get harder to get good results from as it was exposed to more air. This (quart) can I only just opened on Monday.

[Larry]

Not a poly user, but when I have to, I thin it depending on the brand.  Sometimes a lot.  I might even wipe it on.  The cloudiness you are seeing in the can is the flatterer, usually zinc oxide.

[metalspinner]

it is hard to see, but it could be fisheye. You did try different woods with the same result, but with the same brush? Could the brush be contaminated? Did you dip right out of the can, or from another container? Maybe the container is contaminated? Did you wipe down your planer bed with something? Are you spraying the wood off with an airhose? your airlines could be contaminated?

[firefighter ontheside]

I have had this at times.  Sometimes I think it is from putting too thick of a coat on.  The surface dries to a sort of "skin" and then the offgassing from the rest of the finish blows bubbles.  I had a very frustrating time with my walnut table I made for my house.  I had to sand and scrape off the first few coats and start over.  I bought a new can and I used thinner coats.  By thinner, I mean brush on less finish and not thin the poly.

[Downstream]

I have had issues with cloudy finish using semi-gloss so don't use it anymore.  Done the same things you listed and my last chance attempt is to add 50% mineral spirits to thin the finish and turn it into a wipe on mix. Sand everything back to wood and then start wiping on very thin coats building it up slowly.  Usually this works well enough to finish the piece and then I swear to not use semi-gloss again.   Wipe on finish also takes care of any bubbles because you put it on in very thin coats that dry quickly.  I have read that some people with use things like shellac and other similar pre-coats to seal the grain on open grain woods.  I have not done this but others have.  I have had pieces where I had to same down to wood and refinish 8-10 times before it came out right.

[Ljohnsaw]

How many coats are you planning on putting on this piece?  I would finish with gloss or semi-gloss like you normally do and then put one coat of the new stuff on so you don't build up a hazy finish.

[Old Greenhorn]

It's not the haze that is a problem, it's the bubbles or fisheye or acne, whatever you call it. I am not trying to put on a heavy coat. First coat has to be thin anyway, then I sand it and can begin to get even coats. I am using a new brush each time and pulling it right from the can. I can't seem to apply it thin enough to avoid these 'marks' and where their are no marks, it is very streaky. I may sand it down again and try some wipe on to see what happens. I have now spent wasted 3 days sanding, finishing, and re-sanding to take it off and start over. AT 20 bucks a quart this is going to add up, but I am thinking I will sand again today and go get a new quart and a better brush. I am really thinking it's in the can or it's the semigloss itself. But that's what the client ordered and I should be able to do this.  I don't think it is coming from the wood at all. Funny thing is, for semi-gloss, it looks awful glossy. I should have also mentioned this is an exterior oil finish. Maybe I should get the interior version. Not sure what the difference is. I think the exterior is thicker for protective qualities and that may be the issue.
 Thanks for all the advice so far, it's helpful to get me thinking.

[Poquo]

Use the Gloss finish , you can dull the sheen after it cures with 000 or 0000 steel wool . I clean and vacuum my work area before finishing . After applying finish I stay out of the shop so I don't stir up any dust . Good luck every now and then you get one that will try your patience .

[metalspinner]

I buy remnants from a local countertop shop. One "remnant" I bought the last time was a 42" x 9' x 2" mahogany butcher block. 
The finisher spent days, like you on a gloss finish and kept getting fisheye or orange peel in it. He finally just gave up and started over with a new counter.

[NE Woodburner]

You might try putting a couple of coats of gloss on, sanding between coats, and use the semi-gloss as the final coat. I'd also try using a better quality brush with fine bristles instead of the chip brushes.

[NE Woodburner]

Also need to be sure you are not introducing bubbles while stirring the can. I've been too aggressive trying to get all the flattener mixed in and caused bubbles in the can a time or two.

Good luck. I enjoy woodworking, but not so much the sanding and finishing. I always find myself going to fast and paying for it in rework time.

[Downstream]

The other thing I did years ago is switch from bristle brush to foam with much more consistent results.  If I soak in mineral spirits between coats I can reuse on the same piece until edge becomes rough.

[21incher]

It almost looks like silicone contamination. Does it always happen in the same spots? Have you used any spray can lubricant's, cleaners, or penetrants in your shop that could have drifted on it? Sanding won't get rid of it but a wipe down with wax and silicone remover after sanding could help but is not compatible with many uncured finishes.
I would try a good brush and only brush in one direction, Do not wipe the brush on the lip if the can because it creates air bubbles. just press it against the side of the can to remove excess finish after dipping. Only use a clean tack cloth between coats. Good luck

[kantuckid]

Silicone contamination shows as craters, not that stuff thats bumpy. I'd try another brand/can of finish. If the woods as dry as you say and clean as well then somethings is badly wrong with the finish. I seriously doubt blowing air from a system thats not real dry would be it. maybe if you had gobs of water blowed on or oil contaminant in air lines. That's why AB painters use filters in an anal manner. On wood I'm never as fussy as spraying a car with paint or just air. 
Take it off and try again ;D. 
Does the client insist on a built up finish? Poly wipes are very easily applied to table tops and ala naturel look too along with low gloss options. I've never had your result before on wood except for debris like wood dust. 

[alan gage]

You mention it being streaky. Are you spending too much time brushing so that it starts to setup and doesn't have time to self level?

When I get what you seem to be getting it's usually because a bubble has formed after I've finished brushing an area but the poly has set up just enough where the bubble can't quite reach the surface to pop. Or else it does reach the surface and pop but then leaves a raised crater because it was too thick to self-level. Or because I tried to touch an area up with the brush too late and the poly was again too stiff to self-level.

As a couple others mentioned I often thin oil based poly with a some mineral spirits. Sometimes it just seems too thick and I have a hard time getting a smooth coat.

Alan

[Old Greenhorn]

I think I have it.
 But first, let me thank everyone for the suggestions. They are all mistakes I have made in the past and repeating any of them would give 'poor results'. Everyone is on the right track for possible causes. My technique usually works fine, so this one was a real stymie for me. All clean bare wood and dry, and I use good stirring and brush techniques taught to me long ago by a very good pro painter. Clean air, no other work happening, new brushes and material each time. I have done a dozen or more tops this way with fine results.
 Well I started over on the off cut which is about 14x16" off the same slab, sanded and processed right along with the main slab. I am giving that to the client as a little bonus. I got a new can of finish, but this time got the indoor oil based semi-gloss (same manufacturer) I also picked up a good quality brush (it killed me, but I did it) and a foam brush. Re Sanded to bare wood with no defects, wiped off with mineral spirits then dried again. Applied the new finish to half the surface with the foam brush and the other half with the [costly] brush. After half hour of drying, both halves look good and the only defects I can see are clearly spots where I put on too light of a coat or otherwise caused by my hand. They will easily go away on the next coat. It dries as expected. No spots, puckers or any streaking. I think I fixed it and I really think that first can of stuff I had is 'not good'. I will thin that with a little mineral spirits and use it on an outdoor sign or something that doesn't matter much, just to use it up. 
 Now I have to re-sand the main top one more time and start over on that, then the stringer piece one more time. Thanks again for all the good suggestions because one way or the other you guys helped me think it through and find a solution, even if I don't know the cause for certain. I'll let y'all know how it turns out.

[chet]

I had the very same result you experienced, happen to me a while back. I tried to use a unopened can of oil based poly that had sat on a self in my shop for many years. It looked fine in da can, but the resulting finish was terrible.  

[doc henderson]

the stuff in the finish you can see, can you get it on your finger and feel it?  is it precipitated finish?  to use the "bad stuff"  you can try to filter the stuff, and put in a new can, maybe thin 10%, and see if it is good for something.  it is so rough, it looks like particulates in the finish.

[Old Greenhorn]

No Doc, there is nothing physical to see or touch when the finish is first applied. All looks pretty good, but you can se the brush stokes no matter how thick or thin the finish is. My first coats are always thin just to set the wood up for the successive coats. These dots show up in about 10 minutes after I complete the coat, while it just sits, and they get worse for about 30-45 minutes. They are not 'bubbles' I don't know what they are. Bubbles are always round, these are odd little tiny shapes. If I just looked at it in the hardened state I would say it was contamination of some sort. Don't recall seeing anything like it before.  The closest thing I have ever seen to this is precipitated hydrogen in aluminum castings. This happens when aluminum is melted and cast in high humidity conditions and the moisture turns to a gas as the casting cools, creating gas bubbles inside the aluminum. You don't see those, but they clearly show up when you machine the part and it is often junk. I spent the better part of a year trying to troubleshoot this problem with a casting supplier we had. We found the cause, but try as I might I could not get him to clean up his process. 60% of his casting went in the scrap bin and we dropped him.

But this is different, it's not aluminum and I am not familiar with the science as well as I need to be, apparently. Looks like we have it figured out though. First coat dried pretty well and I am back to only having defects I clearly cause by my hand, which are all fixable as I go along. Today I flip all this stuff and get that first cost on the other sides.

[kantuckid]

Mineral spirits work fine but I mostly do my wipe downs using a more volatile solvent that flashes off faster and has a less oily composure. 

Lacquer thinner bought in 5 gal can/bulk is lots cheaper than mineral spirits so mostly my choice. I also watch for banged up gallons of mark downed solvents like xylene, toulene, etc. @ Lowe's markdown shelf along with other "paint" deals. They are better for removing skin oils IMO. 
We have all had finishes spoil our day at times. 

Try having to repaint a car again if you think you've had troubles... :D 
I rebuilt a Subaru for one son as a college car and had to re-do the new front bumper three times from silicone mold release contamination. Fact that he was leaving soon for AZ and ASU made it even more dicey senario. 

My current finish dilemma is my custom self-built entry door. It's white oak and has a large stained glass dogwood design top half then panels below. The issue is UV exposure as every sunny day the sun hits it for a few hours. I use spar varnish that's very pricey but it still gets grungy in only a couple of years. Humidity also is a culprit besides UV. The inside has it's original finish maybe 20-25 years old. I can make it more presentable by wiping down with solvent but not a true fix esthetically. 

[doc henderson]

well I wonder if it is a more solid spec in the old finish, that as the liquid around it contracts, it leaves this particle.  does it leave a proud bump after the finish dries?  for a white finish that is almost fool proof, try the general finish wipe on poly.  you brush or wipe on, then wipe off excess.  and recoat.  very little amber color.  I did a maple top with it.  

[Old Greenhorn]

 Well, I thought I had this licked, and I kind of sorta did, but I only got a lucky coat here and there. I did finish off the short piece and the stringer board. The bottom of the top is fairly good, for a bottom anyway. But the top remains a problem. Last nights results were the worst, gloppy and streaky. I have solved the particle dot problem with better and redundant cleaning steps. Bill kind of nailed it. The stuff is too thick. I can't get the shop up to 75 and hold it there for 24 hours and the stuff is just thick. SO I sanded the top all the way down this morning, then did a test coat with the same poly thinned out with 10% (by weight) of mineral spirits. I think that's got it and it slows the drying long enough for me to get the entire surface done before it begins to cure up. I have a second coat drying now and I am almost afraid to go out and check it.
 I just bought another quart of finish this morning because I have used a quart and a half already trying to get this right, then sanding it all off and starting over. I think I have it this time. I may go up a little on the mineral spirits to like 15%, perhaps more. But I seem to be fighting the genral temps and thinning is required. Tomorrow morning should tell the tale a little better.