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Help - Spray on poly top coat is dull

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Forum topic by buddy4344 posted 12-03-2009 03:42 PM 3065 views 0 times favorited 11 replies Add to Favorites Watch
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buddy4344

13 posts in 2556 days


12-03-2009 03:42 PM

Topic tags/keywords: top-coat dull finish polyurethane question advice request

My shop is in my basement. I built a large (80”) entertainment center for a friend and stained and top coated pieces in the basement, then brought them upstairs for final assembly. Since the completed project finish had some minor scuff marks from clamps, I decided to spray two light coats of minwax semi-gloss (oil based) polyurethane over the work and call it a night. This morning, the piece is a giant dull haze. I am suppose to deliver this tomorrow. Can I simply buff the surface? How soon? Should I re-coat with a wipe on poly-finish? Should I recoat with a paint on water based poly finish (since it will dry quicker)? I need advice – fast.

-- Buddy, Pennsylvania


11 replies so far

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Karson

35034 posts in 3860 days


#1 posted 12-03-2009 03:47 PM

Sorry I’m not going to be any help there. Is the haze some humidity that got captured in the finish while spraying. High humidity can cause that condition.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware soon moving to Virginia karsonwm@gmail.com †

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buddy4344

13 posts in 2556 days


#2 posted 12-03-2009 04:05 PM

Karson, I don’t think so. the re-assembly was done in my kitchen (breakfast table area) and, if anything, this house is too dry with the heating on. My guess is that I went too light on the spray coating, but the question/challenge is – what to do now?

-- Buddy, Pennsylvania

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CharlieM1958

16241 posts in 3678 days


#3 posted 12-03-2009 04:20 PM

.You can try buffing a small area to see if that brings the shine back. If not, I would try wiping on a coat of gloss poly like you said.

-- Charlie M. "Woodworking - patience = firewood"

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buddy4344

13 posts in 2556 days


#4 posted 12-03-2009 04:59 PM

Charlie, idea makes some sense. Since it was a ‘light spray coating’ done at 7pm last night, how long do you think I need to wait before either buffing or wiping on a top coat? I know Minwax often talks of 72 hours for complete drying/polymer formation, but that seems like a long time.

-- Buddy, Pennsylvania

View Scott Bryan's profile

Scott Bryan

27251 posts in 3282 days


#5 posted 12-03-2009 06:49 PM

Buddy, you can re-coat when the surface no longer feels tacky. One way to check this is to lightly sand an inconspicious area with a high grit (400 or 600). If the paper gums up then the finish needs to cure longer. If you produce a fine dust then the poly has cured enough for recoating. Normally you should be able to re-coat after letting it sit overnight, if you use a straight application of poly. Poly that is thinned for wiping or spraying will dry in a matter of a few hours, dependent, of course, on the ambient temperature of your shop.

I have never seen poly do what you are describing. This is a fairly common condition with lacquer that is due to humidity. Charlie’s advice is on target. The sheen you get from a poly application is determined by the final application.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

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buddy4344

13 posts in 2556 days


#6 posted 12-03-2009 08:09 PM

Scott,
Thanks for the added comments. They sound encouraging. of course every answer leads to more questions -

SHOULD I sand entire top (and drawers) with 400 or 600 before re-applying? Will I be better off laying on a new coat of the water based brush on or maybe using the Miniwax wipe on poly (I have both).

Buddy

-- Buddy, Pennsylvania

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Scott Bryan

27251 posts in 3282 days


#7 posted 12-03-2009 08:45 PM

Buddy, at one time I would have said yes you need to do so because I thought that poly needed a “rough” surface to bond to. But the current thinking is that sanding between coats simply to get the next layer to bond is not necessary. So I would sand if you have dust nibs or orange peel and want the final coat to be as smooth as possible. But if you are satisfied with the feel and look, other than the haze, of the current coat you do not need to sand the entire surface.

Of the two I would go with the wipe on poly. I just do not like the look of water based poly. It has a blue cast to it and I prefer the amber tone of oil base.

By the way if you are going to use a wipe on oil base routinely, either by wiping or spraying, you can save yourself some money by making it yourself. Just dilute concentrated poly with mineral spirits about 50:50 and you will have the same product that Minwax sells.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

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buddy4344

13 posts in 2556 days


#8 posted 12-03-2009 09:01 PM

Fantastic. Thanks for the advice. I just tried sanding a little and no gumming, just clean sand dust. The surface looks great except the haze … so i guess I am good to go. I will report back on my results for the thank you and also to log this thread completely for the forum.

-- Buddy, Pennsylvania

View poroskywood's profile

poroskywood

618 posts in 2824 days


#9 posted 12-03-2009 09:31 PM

Hi, I’ve been following this post sorry to hijack. (dumb) Question for Scott: What would I thin Water based poly with?

-- There's many a slip betwixt a cup and a lip.--Scott

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Scott Bryan

27251 posts in 3282 days


#10 posted 12-04-2009 03:41 AM

Scott, I sent you a pm on your question. In answer to it you normally do not need to thin water base poly but if you want to do so then you can thin it with water.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

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buddy4344

13 posts in 2556 days


#11 posted 12-04-2009 05:06 PM

What a difference a day makes. The entertainment center is really looking good. I postponed delivery until saturday to make sure all of the poly is cured but …. here is the story’s ending”
Based on the feedback of the site, I tested a small area with 400 grit sandpaper to make sure the dull coating was dry enough. It was. I then applied a hand wipe coating of poly and waited a few hours. looked like progress, but I could tell the minor texturing from the dull coat was not going to give things a great coating, so I very lightly sanded the piece with 600 grit paper. I then wiped down with some mineral spirits and let dry. Over the course of the evening, I put 3 more coats of wipe on poly on the piece (every 1 1/2 to 2 hours). This morning the piece is looking quite nice.

After a good 24 hour sit, I will probably light buff with old newspapers, put it on the truck and be done with this baby.

Final parting question – This unit is semi-gloss finish. After last coating, do any of you buff? If so, how much and with what?

Thanks again, Buddy

-- Buddy, Pennsylvania

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