Replies

1. 
   SteveSchoene | Mar 07, 2009 05:42pm | #1

   You're descriptions seem basically on track.  I'll quibble a bit here and their, hopefully refining the process a bit. 

   In the satin finish.  For the final rubbing, assuming no more coats will need to be applied, it makes no actual difference whether you use genuine steel wood or synthetic based on the finish being waterborne or not.  It makes a big difference between coats since you are going to apply water, in the form of the next coat, on top of, and potentially rusting, and remaining steel shards. 

   I would never use an ROS here, though with very fine abrolon pads there can be an exception.  Generally, the ROS is too agressive.  Remember, except with evaporative finishes or finishes otherwise sufficiently crosslinked, you generally have only the final coat in which to sand and polish.  If you cut through that final coat you risk "witness" lines.   I recommend staying dry with sand paper.  Yes you use more paper because of clogging, but it is less risky since you see exactly what you are doing.  With experience lubrication is more efficient.  How, or whether, you lubricate steel wool at the end does effect the degree of satin, water is more agressive, wax less, for example. 

   Steel wool is only one of several ways of achieving satin.  You can also use a bit coarser rubbing compound, or with traditional materials pumice (the fine ffff pumice is fine). 

   For Gloss, again you start with 600 or the finest grit that will remove the defects and go to 1200 (CAMI).  It is often best to ignore the popular rule about not skipping grits--jump from 600 to 1200.  It will take a bit longer to be sure, but unless you stop sanding at exactly the right point with each grit, never a stroke too much, you will remove more material than by jumping to the higher grit. 

   Yes, with a gentle touch, you can use a scraper to very efficiently remove dust nibs or defects from the film.  If you are ham handed here you can very efficiently screw up. 

   Now, one more point, rubbing out consumer grade polyurethane varnishes is the most challenging because it is generally much softer than either traditional resin varnishes (ie. phenolic or alkyd) and especially softer than the evaporative finishes such as shellac or lacquer. 

   For best results with varnishes of any kind, be sure to give them plenty of time to cure and harden before rubbing out.  A month is generally considered desirable.  Shellac and lacquer can be rubbed MUCH quicker.  I still like to give them several days at least. 

    

    

1. 
   BG | Mar 07, 2009 06:55pm | #2

   Steve,If I could piggyback on the question, please help me understand the objective of rubbing out? I'm looking at a bench I made about 5 weeks ago and finished up with 7 coats of wipe on poly gloss and 1 coat of wipe on poly satin. It looks good; the satin gave it a kinda smoky look.I don't know if the current look can be improved or what to use.pS. I sanded between coats from the third coat on with finer grits.

   Edited 3/7/2009 10:56 am ET by BG

1. 
   SteveSchoene | Mar 07, 2009 07:42pm | #3

   There are two objectives of rubbing out.  First is to remove surface defects in the finish such as dust nibs or runs and drips.  The other is to adjust the sheen. 

   Rubbing out wiped on varnish can be challenging, especially if overnight drying or more were allowed between the next to last and last coat.  If so the risk of witness lines increases because the last coat is so thin in a situation where it may not have crosslinked sufficient with the prior coats to avoid them. 

   You can buff or polish a satin top coat, likely making it somewhat glossier than it was out of the can.  You probably don't have enough thickness to really sand, and then polish in a full fledged rubbing out process. I can't really tell without seeing in person, but the smoky look may well just be the natural effect of the satin finish.  If there are dust nibs that are bothersome deal with them with a VERY light touch with 600 grit (just enough to get the nibs, not trying to really touch the full surface), and then buff by hand with some steel wool lubricated with paste wax.  You might like that look better, than the off the pad look. 

    

    

1. 
   BG | Mar 07, 2009 09:03pm | #4

   Steve,Thanks. I usually wait about 6-8 hours between the final 3-5 coats of wipe on poly so the light sanding between coats works better. This piece is a recycled church pew so the surface was quite smooth to begin with after striping...lots of squirming on those benches...and good gum too.Have you tried the Watco Satin polish, do you have an opinion?