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Has anyone used rubbing compound, or polishing compound, on wood? I want to remove brush marks before the next coat of poly. Does the rubbing compound have waxes or other ingredients that would inhibit the adherence of the next coat of poly? Should I use pumice and rotten stone instead? Thanks in advance.
Rubbing compound is generally not agressive enough to take out brush marks. I use fine wet or dry sandpaper, like 600 grit. If the surface is flat, use a sanding block and a spray of water.
I use polishing compound to rub out a final finish if I want to make it glossy. Polishing compound is finer than rubbing compound.
If you're using water based finishes, one thing you don't want to use is steel wool. Small pieces will get imbedded in the finish and rust when you put the next coat on.
Mike
Thanks for the info. I have the 600 grit wet/dry sandpaper and I am using an oil based poly. I just did not want to taint the surface so that it would not adhere the next coat.
Just use sandpaper. Anything from 150 to 600 grit should be fine. There's no need to completely eliminate brush marks between coats though, you just need to remove the especially high spots. In fact, some people will apply two or three coats of finish without sanding between coats except maybe to remove dust nibs. The only coat that needs to be perfectly smooth is the final coat, so spend your time and effort there.
In general, 320 grit is about ideal for sanding between coats. Coarser than 220 and you run the risk of sanding marks telegraphing through the next coat, and finer than 400 grit you may not get sufficient "tooth" to assure the best adhesion of the next coat.
As far as brush strokes with varnish, poly or otherwise, you really shouldn't have any. Varnish needs to be thinned. (The labels only say not to thin because of VOC regulations.) Proper thinning should allow almost all brush strokes to flow out before drying. In addition, after brushing out a section of varnish you should "tip off" the surface with a almost dry brush held vertically and just barely skimming the surface to finish leveling and brush strokes and to eliminate any bubbles.
I found my solution to the brush marks. I have some scrap that I have been testing the finish. All of the scraps came out perfect, or near as I can tell. It dawned on me that the scraps were laying flat when the poly was applied. The project has a 56 degree slope and I either got runs coming down or brush marks when I tried to smooth the runs. Solution, I tilted my project until one side was level. I applied the poly and wala, the finish is almost mirror flat. It will take finishing each side individually, but I will get the glass like finish that I am seeking. Maybe this tip will help someone else.
Sounds like a plan. The drip issue is obvious. The brush marks probably appeared when you "over brushed" the already drying finish to get rid of the drips. Tipping it off while it's fully wet is one thing, while it's partially dry is another. If you want a little extra insurance that the brush marks will flow out, you can add a little thinner now that you're working on a horizontal surface. Glad you solved your issues. BTW, different products brush differently. If you ever get really frustrated, consider testing out a different brand.Quote:
Originally Posted by Tommy Emmons
I wouldn't use rubbing compound between coats of varnish for another reason: it's hard to get completely off. You run the risk of sealing in the red stuff in pores between coats. Best to leave it for the final coat so you can dig out if necessary.
I have tried the same approach to finishing. After brushing on oil-based poly on something vertical, I simply place it in a horizontal position to set and dry. It reduces the brush marks dramatically and prevents those aggravating runs that are tough to prevent with oil-based poly.Quote:
Originally Posted by Tommy Emmons