Howdy from Down Under,
I read Sean Clarke’s article on polyuerthane finishes in the latest FWW. I did learn one thing. Not to use oil based stains. This has been a great help. Has anyone out there had experience buffing out a poly finish with a power buffer (the same used in the automotive industry) with a water based compound. My client wants a finish just a bit more glossy than satin but not high gloss. This will also will remove the annoying little dust nibs that invariably will appear on the last coat of finish.
If you would like to reply directly:
Steve Kemp
Many thanks
Replies
I haven't read the article (and won't) but to rule out something forever because of one article seems short sighted.
Sjay,
Welcome. Sagin, one of our more knowledgable contributors, would probably suggest you finish with a high gloss and rub out to the lower gloss that you seek....usning fine grit W&D sandpaper. My two cents beyond that would be to then use shoe polish (another FWW article) ...either spit polish or something less glossy.
The key point being with the above process your in control of the final look and have wiggle room for modification.
Edited 7/9/2004 7:21 am ET by BG
Yes about the car polishing technique.
FWW did an article onjust that topic quite a few years ago. Don't know the issue off-hand.
The guy was using a high speed buffer, the angle grinder type, and was using a product called McGuires rubbing compound for automobiles.
One point he stressed was to practice first, b/c you had to get the technique down so as not to burn thru the finish. Dan
That was Jeff Jewitt, and what he didn't say was you should NOT use this technique on any open-grained woods.
At the time, I had just received this gorgeous 12 foot conference table on a refinishing job. I had never even seen this wood before, and we guessed it was some SA mahogany species. I stripped it, stained and sprayed it, then I tried Jewitt's technique.
I had heard about this before, and was seduced by his seemingly fool-proof, easy-to-follow directions. I bought a buffer and all the Meguir products he used.
Well, I thought this was the best thing since peanut butter. Fabulous is the only word to describe the result, and clients were almost giddy with their pleasure at the outcome.
So it sat in their office for about 3 days, and I got a call asking me if I would come look at the little white flecks that were starting to cover the table -- more every day.
Back it came to be restripped, stained, etc .
I should have called Jewitt, but instead I spoke to a variety of people at Meguir's, and finally connected with some VP who was also into woodworking. He confirmed my suspicions about compound lodging in the open pores, and said there was nothing I could do except strip it off and avoid their products for any open-grained woods. He even advised that I might have the same problem (although less severe) if I first used grain filler.
The moral of this story is that even if an expert writes it down in a book or magazine, that information is not always reliable.
Howdy,
Thanks for the reply. I did see that article some years ago in FWW. The table top thay was buffed out had numerous coats of oil varnish on it, sanded flat btween coats so that the top was dead flat and no exposed pores. In that instance it works. I just need to know if Minwax Wipe on Poly, given the same parameters, is susceptible to the buffing compund in the same way as oil varnish.
Thanks,
Steve Kemp
The wipe-on poly is basically a thinned version of regular polyurethane. If you have enough coats (i.e. sufficient build) on your project, I don't see why the buffing technique would not work just fine.
However, if you are going to try the buffing technique, I think I would brush on at least one coat -- and maybe two, of regular poly. Then you ouhgt not have any problems at all.
If you try it, let us know how it works for you.
If all he is going to do is wipe and buff, this will work. I can not imagine buffing throught the finish. He intends to wipe and rub out (sand, rubbing compound, rottenstone, wax), then I would apply a thicker coat.
My issue with any wipe on product is that after 3-4 coats, the product no longer soaks into the wood, it is laying there on top of it. You wait 5- 10 minutes per instructions and wipe it off. The amount left on the wood is no thin as to be non-existant. If you leave a little on the surface, then you have ridges and wipe marks.
I think you are better applying a full coat of poly, albeit thin, with a foam brush, then waxing it down. If wax doesn't take the polish off, then apply some more with 0000 steel wool; if it is still too shiney, switch to 000 steel wool, or use rubbing compound, then wax.
By going in reverse order, you control the amount of sheen.Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
After stripping the table how did you finally finish it? Polly and 0000 steel wool or what? Or did you use the power buffer W/O the auto compound?
Thanks
(:-)
Windy Wood
From the Helderberg Mountains
In answer to your question, after the table was stripped, I resprayed it with lacquer, and did a simple rub-out with wet/dry paper.
Also, I agree with those who warn against using automotive buffers on polyurethane. Unless you are exceedinly careful, it would be easy to buff through the final poly coat, and thus have problems with witness lines.
The truth is BG I prefer to avoid rubbing out if I can. It takes time and adds cost to the customer. I prefer to apply gloss throughout and finish with the desired sheen as a last coat, and this applies particularly to open grained woods left open grained. Others have detailed the danger here with not being able to properly reach the gloss in the bottom of the pores when rubbing out. Also the problem of leaving the polishing compound in the bottom of open pores has been mentioned.
The reason I prefer applying only the last coat in the needed sheen is that the silica (common matting agent) in the less than full gloss coats can occlude the grain. The polish can also end up a bit milky looking if you put on successive coats of a less than gloss polish.
This applies to oil varnishes, water based varnishes, members of the nitro-cellulose family and any other film forming finish. One trick to achieve the preferred final sheen is to mix a bit (10% or so) of a fully stirred matte or satin finish to a gloss finish thus reducing the glossiness.
With slow drying oil based varnishes there is often, but not always, a bit of debris that rather spoils the final look and rubbing out might be required to get rid of the wee bits and to get the sheen wanted. A gloss finish can be rubbed out to any sheen, but it's a bit more difficult to do this with polishes prepared in satin or matte sheens.
If you expect to rub out, then rub out from a gloss finish is usually the best advice. With oil based varnishes this requires a waiting period between application and rubbing out of about two- three weeks. It takes this long for the varnish cure enough, i.e., cured hard.
Polishing is one of my weaker areas within the pantheon of furniture making skills, but I do what I can. Sliante. RJFurniture
Sgian,
"Polishing is one of my weaker areas within the pantheon of furniture making skills, but I do what I can. Sliante"
Your secret is safe with me....lol
Dear friend,
A favorite for rubbing has been nitrocellulose lacquer because all coats fuse into one and because they cure quite fast.
Polyurethanes do not fuse coats over coats, but each coat is a dry layer on its own, somewhat as one layer of scotch-tape adheres over a previous one.
Have tried rubbing with automotive polishing compounds in the past and it can happen that one 'burns' through a layer and gets small blisters peels, specially if one goes tough on the rubbing, or if for some reason the poly is not well cured there or not adhered quite well yet at a spot. Since poly is tough, then it calls for tough rubbing, which complicates the aproach. Poly is pretty much a plastic layer. Edges are places where the layer is most likely to yield to peel through, and it is quite a challenge to lower the sheen of a glossy final coat of poly due to wood-grain. The valleys glare-through, and it's difficult to get to it, and as one tries to get to it, one burns around it.
Rubbing with 0000 steel wool by hand was possible, but not as an equal to lacquer.
Polyurethanes, alghough dry on the surface and can be handled quite fast, still may need a few days to cure fully. That's to be checked with the manufacturer.
Also, the longer each poly coat takes to dry, the lesser the adhesion between coats could be. Again, checking with manufacturer for recommended times between coatings is advisable.
Based on the above, would also say it's best to leave poly as much as possible as it dries, and would do minor rubbing with steel wool by hand after curing, on the last coat, from a sheen as close as possible to the one wanted.
Good luck.
-mbl-
>>Polyurethanes, alghough dry on the surface and can be handled quite fast, still may need a few days to cure fully. That's to be checked with the manufacturer.
A test is to smell it. If it is still emitting an odor, it is still curing. Varnish, in normal film thicknesses takes 3-4 weeks to fully cure. I should not be "rubbed out" until it is fully cured and even then, poly can be problematic. Polyurethane is added to varnish to make it more scratch and heat resistant. Rubbing is scratching so it stands to reason that rubbing it out to a high gloss can be a problem depending on the product.Howie.........
Just to add some fuel to the fire, poly is usually too soft to buff well, even after curing. That is why people who rub out finishes prefer laquer as it is much harder.
Also, as someone pointed out, since it only mechanically bonds between layers if you rub through a layer you will get witness marks between layers.
Of course, I don't get to work with much in the way of flat surfaces as I only do gunstocks. It might work better on a flat surface.
Michael, you are generally correct.
However, interior rated varnishes contain a higher percentage of solids and cure harder than exterior varnishes. The interior varnishes frequently can be finished to a high sheen using the correct steps of abrasion and polish.
Lacquer and shellac are harder than varnish and therefore lend themselves to finishing to high lusters.Howie.........
Yes, friend, lacquers are harder than straight poly which is tougher or more wear/abuse resistant than lacquer becuase it is more resilient, or plasticky.
Some old automotive lacquers would dry as hard as porcelain and would chip-off and looked like glass where little rocks would hit them, or upon a collision. They are now discontinued.
Also because of its placticity, poly does not 'grind' or pulverize as lacquer but wants to 'peel' or minutely thread upon being abraded, like most plastics.
The dust of lacquer itself helps fill-in pores and even the surface as it fuses itself as the next coat is delivered.
So it is an ideal for rubbing, and would be difficult to equal it with a plasticized finish.
-mbl-
This forum post is now archived. Commenting has been disabled