Problem with streaking in Polyurethane


  #1  
Old 11-08-04, 06:57 PM
alacheta
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Problem with streaking in Polyurethane

I have a recently purchased dining room set (table, chairs, hutch, buffet, coffee table, end table) all of which are valued as midgrade product. They look good, but are made with a softer wood and really don't have a protective finish on them. We have already noticed some scratching and pitting.

As a protective measure I've started down the path of putting some coats of a Satin finish polyurethane on them. I started with a standard type that I brushed on with a foam brush. I noticed when it dried there were a lot of streaks in the finish even after sanding down with 4'0 steel wool and wiping down with mineral spirits. I always apply with the grain and I've been carefull to not over apply.

In a strategic move, I switched to a poly that you wipe with a rag thinking that the foam brush was causing the streaks. I've put on about 4 coats and while the streaks are not nearly as noticable, if you look at the pieces on different angles under the lights you see them.

Can you offer any suggestions at this point? Should I apply any more coats, sand down more? I have only done the three tables and have not started the chairs or the buffet/hutch yet so any suggestions for avoiding this in the future are also appreciated.

Thanks for your help.
 
  #2  
Old 11-09-04, 05:52 PM
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Let it cure.

Couple of points on your efforts.

If the table have been treated with any kind of silicone, the varnish will not take - nothing will. Silicone is present in many waxes. The surface must be cleaned thoroughly - I use denatured alcohol. Then it must be roughened - 320 grit or steel wool. Then use a tack cloth to get all dust off.

I suggest a high quality bristle brush for application - lay it on - don't brush it alot. Let it dry for 8 hours and brush again - keep the layers thin. I usually put on three coats.

Then let it dry and dry and dry - at least 30 days. Varnish (all paints) take time to cure - to really dry. Varnishes today are very strong, but they must be given time to dry. Especially if you are going to rub them out.

Once done, you'll have a finish that will wear for years, even with hot pots.

Be patient.
 
  #3  
Old 11-09-04, 06:37 PM
alacheta
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Thank for the comments tmitchell

The poly did take pretty well. I roughed up the table with 4'0 steel wool before applying the first coat and didn't have any problem with the poly taking. After doing some additional digging, I think the problem is mostly related to my using a satin finish and possibly having the flatteners not stay homogenous while applying.

At this point I think I'm going to do a light sand with 400+ and some water to try to level out the streaks. Then give it another coat and see what happens.
That is unless anyone has other ideas?
 
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Old 11-09-04, 08:42 PM
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Multiple coats of flatted finishes such as semi-gloss polyurethane will look muddy or dull because of the accumulated flatted finish. I find it better to apply gloss coats until the final coat to avoid that accumulation. Actually, I always use gloss and rub it out to the desired finish.

What color are the streaks?
 
  #5  
Old 11-10-04, 08:07 AM
alacheta
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Chris, thanks for the input on the gloss. I'll do that in the future.

The streaks are a lighter color that look analogous to someone who did a really poor job cleaning the furinture with a rag. The are seen when you look at the tables in the light at different angles. And they are definitely from my application as you can see rag marks that go with the grain.

My current strategy is to take a 400+ grit sand paper with a bit of water and lightly sand down the finish to take out what I believe are the ridges of the streaks. Then clean it with mineral spirts, wipe down with a tack cloth and apply another coat of poly but have it be deluted with about 25% mineral spirts. The deluting is an attempt to apply a thinner coat with the hope that this, combined with making sure the satin finish poly is mixed throughly and often will minimize the risk of streaking.

I'm curious to hear your thoughts on this or if you have any other suggetions? Also, should I be switching to a gloss as opposed to a satin even at this point? Finally, you mentioned that you alway use a gloss and then just "rub it out" to get the finish you want. What is the process you use to rub out the finish?

Thanks for you help Chris.

- Aaron
 
  #6  
Old 01-10-10, 07:18 PM
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I'm having same problem with different brands

I'm refinishing my kitchen cabinets (I stripped them and after trying Minwax and Varathane due to the streaking, I switched to using General Finishes stain and Arm-R-Seal Oil & Polyurethane.) I also started by applying several coats of gloss and am trying to finish up with 2-3 coats of satin. But it is still a nightmare with the streaking as described by alacheta once I apply the satin.

Alacheta, did you finally figure out what to do?

Mine, maybe 25% of the time turn out beautiful, the other 75% have the streaking problem. I sand/steel wool them down and reapply until I get them right, but I'm having to reapply the satin several times. I just can't figure it out.

Any advice out there? Is this common as it happened with all 3 brands of polyurethane. Now I wish I had used lacquer, but read that polyurethane wears better. I've been at this for months and want to finish this awful job I started!
 
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Old 01-11-10, 08:29 PM
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I always thin my poly, sometimes to 50%.
It goes on even and levels quickly: sometimes I wipe it on.

fred
 
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Old 01-14-10, 02:44 PM
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Thinning 50% isn't a good idea. It will affect the strength of the coat. Just brush full strength but thinner coats.
 
  #9  
Old 01-14-10, 02:56 PM
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When you say you stripped them how far did you take it? Sounds as though you haven't either cleaned it thoroughly or you've got some silicon (from spray polish) laying on surface. Why so many coats, adding more won't improve it!
Here's my suggestion. Strip one door back to wood, the worst one. Use shellac sanding sealer, this will cap any silicon on surface. Sand back, using zinc stearate paper. Clean off dust, don't use tack cloth. Thin 1st coat. Allow dry thoroughly sand lightly 400 w/dry with or zinc stearate between succesive coats. Clean.don't apply more than 3 coats last one thin. If this doesn't work I'll eat my hat! good luck
 
  #10  
Old 01-14-10, 03:07 PM
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re finishing furniture

Originally Posted by alacheta
I have a recently purchased dining room set (table, chairs, hutch, buffet, coffee table, end table) all of which are valued as midgrade product. They look good, but are made with a softer wood and really don't have a protective finish on them. We have already noticed some scratching and pitting.

As a protective measure I've started down the path of putting some coats of a Satin finish polyurethane on them. I started with a standard type that I brushed on with a foam brush. I noticed when it dried there were a lot of streaks in the finish even after sanding down with 4'0 steel wool and wiping down with mineral spirits. I always apply with the grain and I've been carefull to not over apply.

In a strategic move, I switched to a poly that you wipe with a rag thinking that the foam brush was causing the streaks. I've put on about 4 coats and while the streaks are not nearly as noticable, if you look at the pieces on different angles under the lights you see them.

Can you offer any suggestions at this point? Should I apply any more coats, sand down more? I have only done the three tables and have not started the chairs or the buffet/hutch yet so any suggestions for avoiding this in the future are also appreciated.

Thanks for your help.
What type of polyurethane are you using? If it's water based use synthetic brush. It will help. See my other posts. Silicon is present in household spray cleaners it affects any finishing work you may undertake. Hope this helps! good luck
 
  #11  
Old 01-14-10, 05:33 PM
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Originally Posted by aoliver
Thinning 50% isn't a good idea. It will affect the strength of the coat. Just brush full strength but thinner coats.
Thinning is PERFECTLy fine, what do you think the Wipe-on polys are.
It just takes a couple more coats.
fredaht
 
  #12  
Old 01-15-10, 03:08 AM
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Thinning Coats

Originally Posted by fewalt
Thinning is PERFECTLy fine, what do you think the Wipe-on polys are.
It just takes a couple more coats.
fredaht
My understanding from the original question was that a problem was found streaking on coats that had already been put on. My answer is that I don't think thinning up to 50% is a good idea.

Sometimes you will thin up to 10% as a sealing coat.

Carry on doing it your way, I don't mind!
 
  #13  
Old 01-15-10, 06:09 AM
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Originally Posted by aoliver
My understanding from the original question was that a problem was found streaking on coats that had already been put on. My answer is that I don't think thinning up to 50% is a good idea.

Sometimes you will thin up to 10% as a sealing coat.

Carry on doing it your way, I don't mind!
The OP streaking was caused by brushing on a thick poly, period. You can not apply it evenly, it doesn't level as fast, thus the streaks. That's why furniture mfgs spray and they use lacquer. (it dries fast and they can box it and send it out quickly).
His streaks were minimized by successive coats of wiped on finish. It tended to level the finish across the entire table.

Op, try your next piece with a thinned or wipe-on poly after sanding. Steel wool between coats to eliminat dust 'nubs'. You will be more satisfied. No matter what the thinning ratio, thinner will level faster, the spirits will evaporate, and whats remaing will be a leveler finish. It just takes more coats if thinned!!!
(never use steel wool with waterbase poly).

fred
(I don't know what streaks are, since i always thin my poly)
 
  #14  
Old 01-17-10, 02:05 PM
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In the U.K streaking means there are streaks. Differences in sheen between brush strokes, this is more likely to be due to poor preperation. We use the word runs as in tears for your streaks! When the coating is applied keeping a wet edge - the work is then gone over with a lightly dampened brush with the same finish. This is called tipping no doubt it's called something else over your side of the water!

I would think that diluting/thinning the varnish to the degree you suggest would adversly affect the balance between solid content and solvent and be detrimental to the quality of the coat.

As to using wire wool to take off imperfections (we call denibbing), I would use a zinc stearate paper 320 or 400 between coats. If the surface is flat use a block.

Please bear in mind: I give this information in the spirit of a forum an exchange of ideas and practice. Given the tone of a particular response, I get the feeling that a certain contributor think's it's a personal attack!
 
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Old 01-18-10, 06:22 AM
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alacheta:
One other possibility for the streaks is in the prep before the poly application. Even hand sanding could be the culprit.
Borrow or buy a ROS (random orbit sander) to achieve a smoother surface.

fred
 
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Old 01-18-10, 03:49 PM
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Originally Posted by fewalt
alacheta:
One other possibility
This is all very interesting, but did anyone happen to notice that alacheta's post is 6 yrs old? Monkeymind resurrected an old post.
 
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Old 01-18-10, 10:17 PM
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good point, but monkeymind has a similar problem with streaking.

fred
 
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Old 01-19-10, 07:11 AM
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Yes, I do! Using Arm R Seal

I have 2 cabinet sides left to do and of course they face the sink where any flaws are very noticeable. I already stripped one side and tried again. Called General Finishes and was told to thin 10 - 15% OR mix in a little gloss with the stain. Tried both and they are better, but still a little streaky. They also said that I could use some lemon oil on 0000 steel wool to buff them. That didn't work when I used it on the 100% satin, but might on the satin/gloss mix (I'm going to let it dry a couple more days). But they did turn out more shiny. I am now out of ideas and will have to live with the streaks.
 
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Old 01-20-10, 02:37 PM
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I hadn't noticed! It's one of those timeless questions, that will run, and run (Pun intended)!
 
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Old 01-20-10, 07:31 PM
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That's a good one, aoliver. I know a few people who also had problems with streaking but that was a long time ago and it was usually after they had one pint too many. LOL

It sounds like monkeymind is talking about an uneven surface due to brush strokes, (correct me if I'm wrong) and steel wool is not the answer in that case. Only aggressive sanding (likely with 180 grit, then 220) will flatten out those ridges. Putting the sandpaper on a block sander would help. Thinning the finish, working quickly, spreading the finish as thin as possible, and not brushing too much will help. Tipping off the finish can help, but if it's done after the finish is tacky it can also result in brush strokes.

If the streaks are actually color/sheen changes, I would suggest that maybe the can needs to be stirred with a stir stick. All the goody is in the bottom of the can.
 
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Old 01-21-10, 06:43 AM
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No - I stirred

Arm-R-Seal is a wipe on poly and oil. Their gloss goes on absolutely wonderful - love the stuff. The satin - arghhh! - on some pieces, of course those that don't show, went on great, too. But some left streaking of the flattening agent? Can't be brush strokes as it is wiped-on. And I stirred extremely well. I even stripped one down and tried again - it still streaked. It must be something with the satin poly's. Is there anyway to apply gloss and buff with ??? (I tried #0000 steel wool and it seemed to buff too much, do they make a finer steel wool?)
 
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Old 01-21-10, 03:36 PM
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monkeymind,

My only suggestion now is to try a different medium to wipe it on with(could even try a brush). Other suggestion is to try a different brand of wipe on poly, and stir often!!
You're probably correct, the flattening particles are probably sinking faster than you think.
good luck,
fred
 
  #23  
Old 01-21-10, 03:54 PM
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I think monkeymind's problem is more likely not stirring the pot! Surely brushing on a lacquer isn't going to cause major runs, sorry streaking. It's good practice to rub between coats with zinc stearate it will take out (minor) ripples (sorry another english word). If you rub lightly but evenly you can eliminate minor finishing defects.

I agree with what you say. Except - When you mention about cutting back with sanding paper do you mean sanding paper? It's better to use lubricated paper like zinc stearate because the abrasive particles are more suitable for flattening coatings. Alhough I agree that If radical sanding is needed you could use it.
 
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Old 01-21-10, 03:58 PM
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What type of brush are you using? If it's water based poly use a synthetic brush.
 
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Old 01-21-10, 04:16 PM
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You could get a satin look by using gloss and taking the sheen down. Use a 1000 grit wet and dry, using an orange oil, or water as a lubricant. Lower the grade until you get the sheen you want. Or, you could use a rubbing compound, by hand or use an electric buffing machine.
 
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Old 01-21-10, 04:22 PM
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I tried lemon oil and 0000 steel wool

Oil and steel wool didn't work. Will look into wet/dry sand paper.
 
 

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