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Thread: In Desperate Need Of Help On Polyurethane Mirror Finish!

  1. #1

    In Desperate Need Of Help On Polyurethane Mirror Finish!

    Hello everyone. I am in desperate need of help with finishing a project of mine. I am trying to get a mirror polyurethane finish, but no matter what I do I continue to have problems. My biggest issue is that once I rub out and polish my project, it becomes very glossy, but I can see what looks like smudges and milky white streaks under the finish. I can even rub my finger across the finish and some of the streaks start to gum up and roll off my project.

    I have tried wetsanding the finish down and starting the polishing process over again, yet the same thing continues to happen. For the record I started out with Minwax Oil-Based Brush-On Polyurethane and then decided to go with Minwax Oil-Based Spray-On. I wetsanded the final coat the next day and then I let it sit for 2 weeks before rubbing out/polishing it (it has been humid here the last few weeks if that helps at all). For the wetsand I started with 800 grit and finished at 2000 grit and for the polish I used 3M Rubbing Compound, and Meguires Swirl Mark Remover.

    Everything looks good until I begin the polishing process, what the heck am I doing wrong guys? I have also heard of the Behlens Rock Hard Table Top Varnish, but I am unsure of the durability and I also heard that the rubbing out process is brutal (I am unable to use a powerful buffer on my projects). I'm not sure what to do next, so now I am coming to the experts, thanks in advance for any and all advice given!

  2. #2
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    It does not sound like your process is wrong...

    Your varnish choice is the problem. Poly is tough, it is not very hard. High gloss mirror type finish needs a hard varnish that can be rubbed-out buffed and polished.
    As you are learning poly is so-so at best. That's one of the reasons I say poly is for floors.

    Typically you can't ever get poly glossier than it is off the brush or spray. Once you start to rub it out you end up with less shine. Hard varnishes (Alkyd resin or phenolic resin) will buff to a higher shine than when they first dried.

    Behlens Rock Hard Table Top Varnish is a phenolic resin linseed oil varnish which is very hard. It rubs/buffs-out beautifully, by hand AND it is MUCH MUCH more durable than any Minwax POLY.

    2 weeks in humid weather is not enough time for the poly (or other varnishes) to cure; they need ~30 days in ideal conditions. If you can still smell the poly when you put your nose to it, then it's not cured.
    Last edited by Scott Holmes; 07-28-2009 at 6:32 PM.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  3. #3
    Quote Originally Posted by J. Scott Holmes View Post
    It does not sound like your process is wrong...

    Your varnish choice is the problem. Poly is tough, it is not very hard. High gloss mirror type finish needs a hard varnish that can be rubbed-out buffed and polished.
    As you are learning poly is so-so at best. That's one of the reasons I say poly is for floors.

    Typically you can't ever get poly glossier than it is off the brush or spray. Once you start to rub it out you end up with less shine. Hard varnishes (Alkyd resin or phenolic resin) will buff to a higher shine than when they first dried.

    Behlens Rock Hard Table Top Varnish is a phenolic resin linseed oil varnish which is very hard. It rubs/buffs-out beautifully, by hand AND it is MUCH MUCH more durable than any Minwax POLY.

    2 weeks in humid weather is not enough time for the poly (or other varnishes) to cure; they need ~30 days in ideal conditions. If you can still smell the poly when you put your nose to it, then it's not cured.
    Man I really appreciate you taking the time to reply and help me out. So what do you suggest now? I have wetsanded my projects down again (not to bare wood because they are stained) can I go on top of the wetsanded poly with the Behlens Varnish? or do I have to stick with Polyurethane still? I'd appreciate any further advice from you. Thanks again.

  4. #4
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    Mr Holmes touches on a very good point. Polishing is an abrasive process. Polyurethane was developed (for floors) to be abrasion resistant. It's never going to buff out to a "mirror" finish. Frankly, most varnishes will not, either, although they will get very, very nice.

    In your case, put a barrier coat of de-waxed shellac on the piece over your abraded poly and then apply several coats of a non-poly varnish like the Behlens you mention. The barrier layer is to insure adhesion. Carefully level the finish on the top of the project where it will be seen the most using a block, wet sanding with fine abrasives. Re-coat again several times and re-level. From there, you can put your final coats on and rub them out to the sheen you prefer.

    Yes, this is a lot of work... Do you really need a "mirror" finish?
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  5. #5
    Quote Originally Posted by Jim Becker View Post
    Mr Holmes touches on a very good point. Polishing is an abrasive process. Polyurethane was developed (for floors) to be abrasion resistant. It's never going to buff out to a "mirror" finish. Frankly, most varnishes will not, either, although they will get very, very nice.

    In your case, put a barrier coat of de-waxed shellac on the piece over your abraded poly and then apply several coats of a non-poly varnish like the Behlens you mention. The barrier layer is to insure adhesion. Carefully level the finish on the top of the project where it will be seen the most using a block, wet sanding with fine abrasives. Re-coat again several times and re-level. From there, you can put your final coats on and rub them out to the sheen you prefer.

    Yes, this is a lot of work... Do you really need a "mirror" finish?
    Thanks for the reply, yes I would like a nice, smooth clear finish that highlights and shows off the grain of the wood. I definitely don't want a satin finish, I prefer clear gloss with no visible brush marks. You guys are pretty confident that I can rub my projects out by hand with this Behlens Varnsh?

  6. #6
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    "You guys are pretty confident that I can rub my projects out by hand with this Behlens Varnsh?"

    I just finished (teaching) an Advanced Wood Finishing class this past Sunday afternoon @ WoodCraft... That's what we did; the students went wild.

    Rock Hard Table Top varnish was used on the samples about 2 months ago; so, they were completely cured.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  7. #7
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    I just reread you reply... I definitely don't want a satin finish, I prefer clear gloss with no visible brush marks.

    Are you thinning your varnish before you apply it? Most varnishes, especially the polys are way too thick in the can to use without thinning. It has to do with EPA and VOC regulations. Thinning about 10 -20% works nicely for the Behlen's RHT. It should flow out and brush marks should not be an issue.

    Could be your brushing technique, could be a cheap brush. My varnish brushes are badger hair and cost $20-$60 each. Rockler carries a 2" badgerhair for ~$20 well worth it.

    TIP: Pre-condition your brush... Dip your brush in mineral spirits (MS) before you start to use it; then when it's time to clean it, all your have up in the ferrul is MS. The brush will clean up like a charm. I have 20+ year old brushes that get used all the time and still look new.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  8. #8
    Quote Originally Posted by J. Scott Holmes View Post
    I just reread you reply... I definitely don't want a satin finish, I prefer clear gloss with no visible brush marks.

    Are you thinning your varnish before you apply it? Most varnishes, especially the polys are way too thick in the can to use without thinning. It has to do with EPA and VOC regulations. Thinning about 10 -20% works nicely for the Behlen's RHT. It should flow out and brush marks should not be an issue.

    Could be your brushing technique, could be a cheap brush. My varnish brushes are badger hair and cost $20-$60 each. Rockler carries a 2" badgerhair for ~$20 well worth it.

    TIP: Pre-condition your brush... Dip your brush in mineral spirits (MS) before you start to use it; then when it's time to clean it, all your have up in the ferrul is MS. The brush will clean up like a charm. I have 20+ year old brushes that get used all the time and still look new.
    For the wipe-on polyurethane I didn't thin it at all and the spray-on came in a spray can so I couldn't thin that either. Yeah, when I did use brush-on my brushes were cheap for sure, nothing expensive. I think you guys have convinced me to go with the Behlens instead of the polyurethane this go-round, I will get a can of that stuff and a nice brush and hopefully get some different results this time. I really appreciate your tips, hopefully they will help me avoid any more screw ups.
    Last edited by Anthony Brown; 07-28-2009 at 11:59 PM.

  9. I'm certainly no expert with polyurethane, but I was just wondering: why are you wet-sanding the final coat after only one day?

    The milky white streaks that you're describing sound exactly like what happens to me if I handle or touch the polyurethane finish too early. I don't know why exactly--probably because poly is a reactive finish with some complicated chemical reactions happening while it's curing--but poly has got to be one of the most unforgiving finishes to rub out. One mistake, or one handling or touching of the finish when it's not fully cured, and it's completely ruined.

    All of the previous suggestions seem to be good ideas, but if you can get an otherwise good-looking polished finish (other than the white streaks), you may just need to tweak your procedure a bit.

    Again, I'm no expert with polyurethane, but I'm curious as to why you'd sand the final coat after only one day? With high humidity, things can take much longer than usual to cure/dry. Once it's tack-free and dry to the touch, (hopefully within a day) I like to have a fan blowing on the surface of the finish to speed things up. But you definitely don't want to sand/polish/handle polyurethane too early, it's very unmerciful in my experience.
    Eric Meier

    I Shellac.

  10. Quote Originally Posted by Eric Meier View Post
    I'm certainly no expert with polyurethane, but I was just wondering: why are you wet-sanding the final coat after only one day?

    The milky white streaks that you're describing sound exactly like what happens to me if I handle or touch the polyurethane finish too early. I don't know why exactly--probably because poly is a reactive finish with some complicated chemical reactions happening while it's curing--but poly has got to be one of the most unforgiving finishes to rub out. One mistake, or one handling or touching of the finish when it's not fully cured, and it's completely ruined.

    All of the previous suggestions seem to be good ideas, but if you can get an otherwise good-looking polished finish (other than the white streaks), you may just need to tweak your procedure a bit.

    Again, I'm no expert with polyurethane, but I'm curious as to why you'd sand the final coat after only one day? With high humidity, things can take much longer than usual to cure/dry. Once it's tack-free and dry to the touch, (hopefully within a day) I like to have a fan blowing on the surface of the finish to speed things up. But you definitely don't want to sand/polish/handle polyurethane too early, it's very unmerciful in my experience.
    Thanks for the reply. Actually I was told (obviously wrongfully) that you could wetsand the poly within a day or two, but that you had to wait 2 weeks for it to cure to rub out/polish it. Also, I saw somewhere that oil-based finishes take 2 days to cure while water based finishes take 30 days. There is so much misinformation out there on this stuff, that is why I came here to the pros for some real answers!

  11. #11
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    Quote Originally Posted by Anthony Brown View Post
    Thanks for the reply. Actually I was told (obviously wrongfully) that you could wetsand the poly within a day or two, but that you had to wait 2 weeks for it to cure to rub out/polish it. Also, I saw somewhere that oil-based finishes take 2 days to cure while water based finishes take 30 days. There is so much misinformation out there on this stuff, that is why I came here to the pros for some real answers!
    Oil base isn't going to cure in two days. Try a month. Weather has a lot to do with curing. I have never tried to buff poly, but I have polished automotive clear coats on guitars that are mirror finishes.
    Phil in Big D
    The only difference between a taxidermist and the taxman, is that the taxidermist leaves the skin. Mark Twain

  12. #12
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    I think the white streaking you're seeing could be caused by the humidity you speak of. I know that's true of other finishes. Humid weather can cause several problems. Hope you get it solved. I've been there, too, where you redo a finish a number of times while trying to learn the secret.

  13. Quote Originally Posted by Ken Casser View Post
    I think the white streaking you're seeing could be caused by the humidity you speak of. I know that's true of other finishes. Humid weather can cause several problems. Hope you get it solved. I've been there, too, where you redo a finish a number of times while trying to learn the secret.
    Lol, That's exactly where I am right about now. This project has taken almost my whole summer to complete because I keep fouling up the finishing stage. Oh well, I'll get it right one way or another.

  14. plastic polishing cream by Novus

    I found this thread two years later; however, for those of you looking to polish polyurethane to a mirror finish it can be done. I was searching for something to polish my plain old polyurethane when dry sanding to 2000 was not working. From reading the above thread, I thought it was not possible, and put my project away for the night. Today, I picked up my plastic polishing stuff and gave it a try. It totally works, with not a lot of elbo grease.

    It is a plastic polishing system of 3 creams by Novus. I purchased them at Tap Plastics, but have seen them other places. Since I have sanded to 2000, I started with the 2nd cream, for minor scratches. Using this cream and a Viva towel, My sculpture now shines as if it was wet was water or oil! I topped it off with the #1 polish as well, but there was not a noticeable difference from the #2 cream.

    To recap: I applied about 6 layers of polyurethane by varathane. I waited 3 days then sanded with 300. Then 600, 1200 and finally 2000. The 300 and 600 was a paper based sandpaper. The 1200 and 2000 are a cloth based and I found them to work better than the 1500 on paper. Last I used #2 scratch cream by Novus. This really made the surface smooth and crystal clear like a mirror; exactly like the wet polyurethane looked, except without brush marks.

  15. #15
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    Are you using a water-borne poly or an oil based poly? You can make poly shiney; you can't make it as shiny as a harder varnish.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

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