Speckles in polyurethane finish.

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Forum topic by justinwacker posted 09-03-2016 09:26 PM 265 views 0 times favorited 11 replies Add to Favorites Watch
View justinwacker's profile


4 posts in 93 days

09-03-2016 09:26 PM

Hi guys,

I used a thinned poly, 3 or 4 layers, and after using a 400 wet paper to light sand my dust nibs I have these speckles where every nib was.

In shade they’re hard to notice but direct sunlight really brings them out.

I’m hesitant to use higher grits, it’s already baby bottom smooth, but would sanding with higher grits polish them out?

Any other ideas? I am also concerned that maybe they’re not dust nibs, but a cotton rag that started to fall apart while wiping the poly.

11 replies so far

View sawdust703's profile


270 posts in 837 days

#1 posted 09-04-2016 12:48 AM

From the looks of the picture, your wood weren’t clean before you stained it. No offense, but, when you done your final sanding, you had places fill up with dust from sanding. To prevent this, I blow the project completely down with the air hose, then wipe the work piece down with a clean rag & mineral spirits, then blow dry it again. Be careful after you wipe it down with mineral spirits. Wear poly gloves to finish cleaning it up so you don’t leave any fingerprints on the wood. They will show through the stain. Once your work piece is completely dry, stain it, & leave it to dry. Before you spray the poly, make sure those areas are still clean. Start in w/your poly. Allow it to dry overnight. Then buff it out with 220 paper. Remember, go all the same direction because your sanding will show as scratches if you don’t. Blow the dust off the project, wipe it down, & apply your next coat. This is my experienced way of handling your situation. Good luck, & God bless.

-- Sawdust703

View jwmalone's profile


769 posts in 120 days

#2 posted 09-04-2016 01:07 AM

Hard to tell, But ill agree with sawdust703, something was contaminated. That fine dust can be hard to see until its to late, also I rarely use wipe on Polly but be mindful of what you use to wipe it on with and clean it with. Never use old t-shirts and such, occasionally the dies, detergents and what not in the cloth will cause the contamination, even if its clean (not always but I don’t chance it). . I use a brush but that’s my preference. so no amount of prevention can be considered over kill. . Just sand it down start over.

-- "Boy you could get more work done it you quit flapping your pie hole" Grandpa

View nightguy's profile


213 posts in 80 days

#3 posted 09-04-2016 01:09 AM

I dont understand most of your Thread? Did you use 400 between coats? What did you use to apply it with?
I dont know where Sawdust 703 is coming from with gloves, spraying ect. Reminds me of Pulp Fiction, time in reverse.

View jbay's profile


696 posts in 316 days

#4 posted 09-04-2016 01:12 AM

The “nibs” that your talking about must have been there when you stained. Or could have came from the rag you stained with. (You didn’t mention how you stained or prepped the project.)
They took color, then when you sanded them off the color they went away leaving the speckle. You need to make sure the “nibs” aren’t there before you stain.

It’s hard to tell from the pics but from my experience, the whitish color in the grain can come from stain that isn’t completely dry especially minwax.

-- Glad to discuss ANY of my comments! Understanding why someone said what they said may help you understand the person.

View nightguy's profile


213 posts in 80 days

#5 posted 09-04-2016 01:32 AM

What wood is that?

View BurlyBob's profile


3450 posts in 1683 days

#6 posted 09-04-2016 01:51 AM

If your wiping, cotton is the wrong thing to use. Try a polyester cloth, it doesn’t shed lint. Fold it in a rectangle and use the fold like a sgueege.

View justinwacker's profile


4 posts in 93 days

#7 posted 09-04-2016 02:45 PM

Hey people,

A little more info. I used the “t shirt material rags in a bag” that you can buy at Menards in the paint department. Fresh rag every time for wipe downs and layers of stain, poly etc.

I did blow the project clean, then wiped with a dampened cotton rag (mineral spirits). Let dry.

It is pine. I stained with Varathane oil based, applied with cotton rags. Dried a full day.

Another wipe down with mineral spirits damp cotton rag. I used my fingers to feel for any bumps and was smooth at this point.

My thinned with mineral spirits poly was, again, applied with a cotton rag, 2 very thin coats. Let dry overnight. Hit with 400 wet barely any pressure just to smooth. Again, seemed smooth.

2 more coats poly, less thinned. Again, rag. Again, 400 grit next day. Super smooth. Nice satin sheen. But these spots….

I’m really leaning towards one of my rags must have been worse than previous experience, and deteriorated into one or more of my poly coats….. On the corners of the project I can see what look like bits of fiber from the rag.

I’ve never used a polyester applicator/rag, is there a place you can load up on those for cheap? I really like the thinned poly and the way it goes on, but haven’t tried the thinned stuff with a brush, foam or natural. Maybe I’ll have to give that a go.

Thanks as a always for a round of opinions. Honestly, because this project looks great in most lighting I’m not going to refinish it, but I want to avoid it in the future and product better quality finishes

View BurlyBob's profile


3450 posts in 1683 days

#8 posted 09-04-2016 03:14 PM

Justin, a lot of you problem in the cotton rag! Scrap that idea totally. I use a piece of polyester folded and wrapped in a piece of a women’s nylon. Works like a champ. Find some old piece of clothing at a yard sale or buy some at a fabric store. It’ll save you a world of grief. Trust me I learned the hard way just like you.

View nightguy's profile


213 posts in 80 days

#9 posted 09-04-2016 03:20 PM

I use the cotton T shirt material from Menards with no problems with wipe on oil Poly or 1 1,2-2lb cut Shellac. I always shake the piece of clothe a few times b4 I start maybe I have just been lucky over the past 7 years.
My thoughts are air borne dust possibly. Who knows.

View a1Jim's profile


115166 posts in 2994 days

#10 posted 09-04-2016 04:05 PM

My guess is that you’re getting what Charles Neil calls push back,your finish has filled the grain of the wood and as it starts to dry the excess finish bubbles out . A couple other alternatives is that your finish is old or contaminated or that your first coat was not completely dry.

-- Custom furniture

View oldnovice's profile


5642 posts in 2785 days

#11 posted 09-04-2016 04:34 PM

I have never seen that problem and, believe me, I have created a lot of my own!

BurlyBob, I use lambs wool for applying poly!
These are sold at Lowe’s for floor finishing so I cut them down to size depending on the project.

-- "I never met a board I didn't like!"

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