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Help: Pigtails in my Polyurethane Finish

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Forum topic by Bulkhead posted 12-02-2016 08:18 PM 684 views 0 times favorited 14 replies Add to Favorites Watch
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Bulkhead

23 posts in 1371 days


12-02-2016 08:18 PM

I have been working on two large soft maple desktops for a couple weeks and have done something stupid I’m afraid, so I’m wondering if anyone here has a solution gained from the same mistake…

I have stained and sprayed General Finishes High Performance gloss poly on the desktops. They were looking great. These are for built-in desks, one is 11’5”, the other about 9’. After milling, glueing, planing, belt sanding and RO sanding, and 5 applications of GF dye stains, I started finishing. I sprayed 4 coats of the poly and was getting an okay surface, but had bumps when looking across the surface of the large desktop with or into a raking light.

Here’s where I fear I went wrong.

I waited 3 days (just due to other things being dealt with, not specifically to let the finish harden) before sanding with 220 on the ROS. I wanted to get to a smooth, flat surface before spraying the final coat of poly which I thinned in an attempt to get it to really flow out and lay down as smoothly as possible.

I vacuumed and wiped down the surface and I don’t remember if I thought they would vanish in the finish or if I didn’t see them.. but I sprayed about a 3 mil coat I had hoped would be the final.

I now see pigtails throughout my finish.

What do I do now? The poly has dried for 24 hours. GF’s directions say wait 2-4 hours before light sanding and recoat.

I really don’t want to risk sanding through the coat I just applied and down into the 4th where the pigtails are, but I am thinking that is what I need to do.

Are there any other approaches I can take? If I sand down, what do I use to avoid creating more pigtails or otherwise creating more issues? BTW: I have abralon disks from 1000g to 4000g and a 1/4 sheet sander and various wet/dry papers.


14 replies so far

View Fred Hargis's profile

Fred Hargis

4761 posts in 2331 days


#1 posted 12-02-2016 08:30 PM

The pigtails have to be removed or they will show. If they are so obvious they will be seen I don’t know of another option. What I’ve always done was to sand after using the ROS; by hand with the grain. With pieces the size of yours, you might look for a 1/2 sheet sander to do that.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Bulkhead

23 posts in 1371 days


#2 posted 12-03-2016 12:28 AM

Upon looking closer, and when trying to take a picture, I should add that the pigtail swirls are only visible where you look toward a light. Off light, they are not visible.

Also, the coat I applied on the problem desktop seems to me to be thinner than the other which didnt have this problem. Perhaps I sprayed too thin a coat?

If the pigtails are tiny shallow lines refracting light, could they be minimized with a couple more coats, each presumably filling in more? Then when I flatten (more carefully than last time) and rub out the surface, might they be not visible?


Pigtails visible in reflected light. Image quality due to mobile phone pic.

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Fred Hargis

4761 posts in 2331 days


#3 posted 12-03-2016 02:50 PM

You can try, but they’ve never went away on stuff I’ve done. If they’re barely visible maybe the thing to do is not worry about it. We typically look more closely at our own stuff than others will.

-- Our village hasn't lost it's idiot, he was elected to congress.

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jbay

1857 posts in 737 days


#4 posted 12-03-2016 03:28 PM

I would hand sand it with 320 going back and forth in straight lines with the grain,
then I would spray another coat, only thinning material enough to spray properly, and I would put on a pretty good coat not to light but not overly heavy.

-- If anyone would like to see my Portfolio, PM me and I would be glad to send you the link.

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mahdee

3828 posts in 1605 days


#5 posted 12-03-2016 04:22 PM

I would give it few more coats of straight from the can, wait 3-4 days, sand it smooth and finish it with a rub on poly. Or you can go down in grits to wet sanding it to 1000 or more before buffing it. Since the surface is irregular right now, any additional coats sprayed will put an even coat over the surface. So, the idea is to create a thick enough film so it can be sanded to an smooth surface.

-- earthartandfoods.com

View corelz125's profile

corelz125

314 posts in 814 days


#6 posted 12-03-2016 04:28 PM

I have had the same problem and the only way they go away is by sanding it by hand like how Fred mentioned.

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Bulkhead

23 posts in 1371 days


#7 posted 12-03-2016 05:23 PM

Thanks for the advice guys. It helps to have some reassurance that my thinking is mostly on track.

I am skeptical, but hopeful that I can resolve the issue.

If I wipe the the surface down with a wet rag, the swirls and pigtails are not visible until the water evaporates which gives me hope that they can be obscured by more coats of poly.

Im thinking, similar to the advice given, that I’ll wet sand with 400 by hand with a block in the direction of grain and then spray another coat.

I dont have any 320 on hand at the moment. I dont want to sand too aggressively but I guess I dont want to make progress any slower than necessary either..

Im curious about the suggestion to finish with a wipe on. Can you comment on the advantages of such? I’ve sprayed these pieces because they are so large and I thought the poly would set up so fast I would get overlap and visible start / stop marks.

View Carloz's profile

Carloz

979 posts in 429 days


#8 posted 12-04-2016 05:41 AM

Thd only right way is to take a sander and sand everything down to bate wood. Then start over. Take it as learning experience. Heck once I did exactly that 5 times on s piece of furniture before I got it right.

View jbay's profile (online now)

jbay

1857 posts in 737 days


#9 posted 12-04-2016 05:49 AM



Thd only right way is to take a sander and sand everything down to bate wood. Then start over. Take it as learning experience. Heck once I did exactly that 5 times on s piece of furniture before I got it right.

- Carloz


The pigtails are in the finish. There’s no reason to sand it back to bate wood. (whatever that is) lol

-- If anyone would like to see my Portfolio, PM me and I would be glad to send you the link.

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mahdee

3828 posts in 1605 days


#10 posted 12-04-2016 02:21 PM

You can brush on or spray the wipe on and thin it further if needed. Once you have the entire surface wet then wipe it off. The wipe on is too thin to create uneven surface.

-- earthartandfoods.com

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Bulkhead

23 posts in 1371 days


#11 posted 12-04-2016 06:52 PM

Success!

I wet sanded in direction of grain w 400g and felt block.

Sprayed more unthinned GF High Performance. Swirls are mostly gone. I feel good that they will be when I repeat the process.

Regarding spray vs. wipe on: I have been using water based poly for ease of cleanup and speed of drying. It is amazing how fast it dries! I can touch it in an hour without leaving fingerprints. Seems to fully cure in 24 hours.

But, because of that I don’t think it can be wiped on a project as large as mine.

I think I want a satin or semi-gloss sheen (these are desktops for teens). I’ve used gloss thus far thinking I will rub to desired sheen although I’m going to have to learn how to do that. Many various techniques described online..

Given that I intend to rub out the finish for a very smooth surface and seeking a satin or semi-gloss sheen, should I switch to an oil based wipe on or continue to spray the water based GF poly?

If wipe on, which product do you like?

Thx

View Fred Hargis's profile

Fred Hargis

4761 posts in 2331 days


#12 posted 12-04-2016 07:08 PM

I make my own wipe varnish by diluting my regular brand (P&L 38 alkyd varnish) 50/50 with MS. Most of the store bought stuff is diluted to a much greater degree. As for switching to an oil based product at this point, given the problems you’ve had so far I’d suggest you wait to the next time to start with the oil based. If you have a path to success, call it a win and move on.

-- Our village hasn't lost it's idiot, he was elected to congress.

View CharleyL's profile

CharleyL

221 posts in 3202 days


#13 posted 12-04-2016 07:09 PM

If for teens, I wouldn’t worry at all about the marks. Just look again after they’ve used them for a few years and you won’t even be able to find these marks what with all the other marks that will be there. Rivets on blue jeans
make all kinds of marks, not to mention the marks left by other strange things that get piled on their furniture. DAMHIKT. (I survived raising 4 teens)

Charley

View Bulkhead's profile

Bulkhead

23 posts in 1371 days


#14 posted 12-05-2016 04:34 PM

Thx all! Another coat of unthinned poly sprayed to full wet film and they look great again. No pigtails!

Sure would be nice to not have to contend with nibs and the occasional gnat stuck in my finish!!

Now to the next learning opportunity: how to finish the finish…

I may have to start another thread specific to rubbing GF water-based poly…it is a different beast.

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