# how to repair scratching poly on desktop?



## wdedalus (Feb 27, 2009)

About six months ago, i made a bunch of built-ins for my home office out of solid ash ($1,000+ on lumber). i finished with 3 coats of minwax stain followed by 3 coats of minwax satin poly. for the desktop itself, i did an *additional* 3 coats (6 total) so I'd have an extra-strong surface for the hi-traffic area.

it came out beautifully and installed well. but six months later, the desktop looks like crap. it appears that the poly is scratching - which leaves white marks all over the place (which stand out against the dark espresso color of the wood).

download pics of problem here:
http://www.yousendit.com/download/U0d6bUpTZ2c1UjUzZUE9PQ

now i'm thinking i should have just oiled it and not used poly at all. i thought poly was supposed to be *the* most durable finish there was! is there anything i can do now to fix it? something i could put on top of this to correct the problem, without having to strip down and re-finish from scratch (which would make matching the rest of the room difficult).

after all the cash and effort, this problem is very frustrating... i'll never use poly again.


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## CivilEngineer13 (Aug 29, 2008)

Polyurethane is extremely hard and inflexible, so while it sits on the active wood it starts to loosen it's grip by teeny tiny amounts at a time, especially where there are two boards joined together edge to edge, because the density of the boards would be slightly different than each other, so would expand and contract differently. The wood is flexible, as are natural finishes, so they can generally contend with each other, but polyurethane just sits there kind of ho hum while it loosens up. So it makes furniture with cracks in the finish along a joint, or some of the finish is missing, or light areas like there may be a large bubble under the finish.

From what I can gather, the wood may not have be completely dry, or the time between your poly coats was too short, so while the poly on top is now 100% cured, the previous 5 coats my not have been... not good.


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## firehawkmph (Apr 26, 2008)

Wd,
In your pics it looks like it is not a 'scratching' problem. It looks like the coats did not adhere to each other. Did you sand in between each coat? Did you follow the directions from the manufacturer as far as how long to wait between coats? I have never had polyurethane come off like that. I have my original computer desk that looks like a big table, that coincentally happens to made out of ash. I put a coat of golden oak stain on it and three coats of polyurethane on it. Still looks good after 22 years. You may have to sand that top down to get rid of the peeling and start over again.
Mike Hawkins


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## wdedalus (Feb 27, 2009)

man, that seriously sucks. i followed the directions to a T. cured each coat for 24 hours before applying the next, lightly sanded with steel wool between each coat (then wiped down to remove any particles). chances are, it will be years before i have the patience to take the whole room apart to re-finish the top. it's built into a bay window, so isn't going anywhere; i'll have to do it in place. kicking up all that sawdust in a room with printers & computers would be a nightmare.

when i do re-finish, think i can sand lightly with a 220grit on orbital sander and try to keep my stain intact underneath? and just re-apply the poly (or oil)? or do you think any attempt to sand will strip off the color and make it look blotchy?

minwax has made a lifelong enemy of me with this junk.


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## soniferry (Feb 27, 2009)

se a really fine sandpaper or superfine steel wool to very lightly buff the scratch and surrounding area so it's smooth again. Make sure you work in the same direction as the wood grain. Clean the area with a damp cloth to remove any dust and dirt and then let it dry completely. If you tend to be impatient, grab a hair dryer to speed things along. Next, use a wood marker to fill in the scratch and blend it with the rest of the wood. Now you want to touch up the polyurethane to keep the floor protected. Dip only the tips of the bristles into some polyurethane and then brush it onto a paper towel to remove most of the finish. Use your dry brush to cover the area. This dry brushing technique will blend the repair with the floor rather than making it stand out. Finally, put some painters tape around the area to remind people not to step on the repair for 24 hours.


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## johnnie52 (Feb 16, 2009)

I have never seen any poly do what is in your pictures unless something got onto the surface and wasn't properly cleaned away before laying down the finish.

This almost looks like either water droplettes, or sweat, or oily hands touched the surface and were not cleaned properly before the final coat of poly was applied.


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## GeorgeC (Jul 30, 2008)

soniferry said:


> se a really fine sandpaper or superfine steel wool to very lightly buff the scratch and surrounding area so it's smooth again. Make sure you work in the same direction as the wood grain. Clean the area with a damp cloth to remove any dust and dirt and then let it dry completely. If you tend to be impatient, grab a hair dryer to speed things along. Next, use a wood marker to fill in the scratch and blend it with the rest of the wood. Now you want to touch up the polyurethane to keep the floor protected. Dip only the tips of the bristles into some polyurethane and then brush it onto a paper towel to remove most of the finish. Use your dry brush to cover the area. This dry brushing technique will blend the repair with the floor rather than making it stand out. Finally, put some painters tape around the area to remind people not to step on the repair for 24 hours.


Good afternoon to you in the UK. To what post are you replying? This one was about repairing a desk top.

George


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## Julian the woodnut (Nov 5, 2008)

Was the stain and poly both oil based? I have seen waterbased poly come off like that before after using linseed oil, which is the oil in minwax stain, as the basecoat.


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## wdedalus (Feb 27, 2009)

yep, poly & stain were both oil based, and both made by minwax. the stuff in the pictures shows *big* spots - where there's really visible problems that show up easily on a picture. but the entire area where i work has tiny little white dots and lines all over it. we have a cat who likes to jump up on the desk to sit in the bay window & bask - and any time his claws touch the surface you get a white line.

think i could strip off *just* the poly and keep the stain, to avoid stripping all the way down to the raw wood and starting over from scratch? oy vey...


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## Rick Mosher (Feb 26, 2009)

*Rick Mosher*

"3 coats of minwax stain followed by 3 coats of minwax satin poly"
3 coats of stain is a potential adhesion problem. You are building up a film of pigment which is not allowing the poly to wet into the wood and achieve a good bond. You should only use 1 coat of minwax atain and wipe it off thoroughly. If you need a deeper color you should use a dye stain first.

"lightly sanded with steel wool between each coat (then wiped down to remove any particles)."
Steel wool will not roughen up the surface enough to get a good mechanical bond. 320 sandpaper MINIMUM 280 would be better. Poly is a finish that REQUIRES a good mechanical bond between coats or it will peel off. Shellac and lacquer re-wet the previous coat so steel wool or scotch brite pads are OK. I am afraid that you will have to remove the finish to make it right. I hope this helps...


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## wdedalus (Feb 27, 2009)

hey rick, i never knew that (about using 280 grain sandpaper between poly coats instead of steel wool).

do you think, now that the top-coat and those underneath have had a good long while to cure, that if i sanded the entire desktop with a 280-grit sandpaper (paying special close attention in the areas where there are dots and bubbles), i could then put one more coat of poly on - and resolve this problem for good (without having to re-finish)?

there's hope yet...


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## Rick Mosher (Feb 26, 2009)

That would be your call. However if there are areas with bad adhesion a new coat won't do anything to fix the problem so you could have more failure in the future.


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