Rubbing out a lacquer finish

B

Bob Seibels

Member
A couple of months ago I completed a Baltimore card table (Steve Latta's plan from FWW).  The top coat was 10-12 sprayed-on layers of Hydrocote Resisthane gloss waterborne lacquer.  I waited several weeks before attempting to rub it out.  My goal was to achieve a high gloss (mirror-like) appearance on the tops.  I used successive grits of wet-dry sandpaper with water-diluted Wool Lube from 400 on up to 2000.  At that point, I switched over to a rottenstone/water slurry and damp cotton pads.  After a LOT of rubbing, I achieved a brilliant, glossy finish on the upper surface of both half-circle tops.  Then, I put some soft cotton padding on the front half, folded the rear half down, and went to work on the back of that panel (which routinely faces the wall, but can be a "working" surface if desired).  After a lot more elbow grease had been expended, I achieved a similar glossy finish on the back side.  When I unfolded the top, I discovered to my horror that the cotton padding had left fabric marks on both of the tops.  Although it was completely cured and hard prior to my rubbing it out, I evidently had managed to soften up the finish with the Wool Lube and/or rottenstone.  I then waited a few more weeks for the finish to completely harden again, and started all over, this time replacing the rottenstone with a 3M automotive polishing compound called Finesse It II.  The same thing happened again (although not as bad this time, because I was much more careful in padding the two half-tops). 
I spoke to a technician at Hydrocote today, and he said I should not use any water-based products to rub out a water-based finish.  Apparently, they can soften a "cured" finish.  He suggested that I use baby oil or mineral oil, which, according to him, would not soften the finish. 
A year ago I used the above technique on a shellac-finished huntboard, and it, too, seemed to be softened by the rubbing out process.  It buffed out to a beautiful gloss, but a candlestick placed on the surface left a mark.  Now, a year later, the finish is hard as a rock and safe to place items on.
Has anyone ever encountered a situation like this while rubbing out finishes?  Should I rub out the table in stages, leaving the top halves to sit for a few weeks before I try to work on the bottom? 
I'm beginning to understand why most woodworkers shy away from gloss finishes........

Bob Seibels
 
I've encountered this with nitrocellulose lacquer when I failed to wait at least two weeks before rubbing it out.

It left a mess, grey areas, bare areas and dull areas.  Net result, do over.  Lesson learned, now I always wait 3 to 4 weeks before touching the stuff.

Herman
 
I feel your pain, Bob. Everything you are doing is pretty much on the money but you have encountered the ambiguous "cure time" or "dry time" of the finish. I don't think it is economically feasible to conduct a final rubbing out in the shop with anything but a catalyzed finish. Lacquers take a long time to really cure, which is why they are so problematic. Shellacs, while preferable for the high gloss, remain soft for months. Let's face it, you can't do better than Finesse It. What I find remarkable about shellac finishes is that they can be rubbed out to a beautiful gloss by hand. Literally by hand. I put a little rottenstone on the heal of my hand and rub until my arm aches. This produces a certain amount of heat and I have found that when the heat generated becomes uncomfortable it is time to back off. After the rottenstone stage I just rub with a bare hand. Does this heating process hasten the curing time? I don't know absolutely, but I get a lot of "how'd you do that" 's from people.
Rubbing out conversion varnishes is obviously the best choice but there are no shortcuts. You either end up with a perfect, beautiful glass-like finish or you don't. It requires hours of careful hand rubbing. It can't be done by swirling machines with soft pads. The higher the gloss, the more obvious the method used to create it. But one thing these modern varnishes do provide is a comparatively higher predictability in cure time. Any rubbed finish will benefit from some sort of lubricant like mineral oil but used very sparingly. Remember, in the final analysis the oil film also has to be removed entirely without affecting the finish. Naptha is usually good but effects shellac to some degree, enough to remove that glass finish. If a light mineral oil is used you are better for it. I use the tiniest speck of oil on a finishing pad with just a hint of alcohol for shellac. After this I rub by hand as described above and it seems that the oil film is removed in the process. Try this with the waterborne lacquer and let me know how it pans out.
 
Bob, I agree with previous posts.  You also recognized something that I learned some time ago.  If I intend to finish the finish of a secondary surface, I do it first.  Always waiting to the very last operation to do the "show" side of any project.

Feel your pain.

Good luck.

Ken
 
For those of us who have found ourselves immersed into the intricacies of finishing wood there should be felt among the cogniscenti a great pity. It is one thing to produce a good piece of furniture. To finish it properly is another thing. My personal view is that, having created this conundrum, I am duty bound to bring it to it's resolution. There have been times when I have reconciled myself to my inadequacies in this regard and turned a piece over to people who do nothing but finishing. It is from these people that I have learned valuable lessons. It is out of these experiences that I have learned to stick to what I know. These methods include using simple remedies for the vast majority of my work ( a brilliant sheen can be obtained from off the shelf varnish) to the more elaborate methods of working with shellac. I am not in a position to invest in a spray booth and have become entirely disenchanted with brushed on lacquers. I have found that the simplicity and reliability of the various methods of applying shellac finishes consistently produce the best result. But, regardless of the chosen finish, I must reconcile myself to the fact that a decent finish will inevitably require more time than is economically warranted. As I have expressed before, the glass or mirror finish, is the most troublesome, for as we bring out this shine the imperfections become more and more obvious. Developing techniques for dealing with a wide array of spectacular results from every available finish is for me impossible so I rely on this most versatile material, shellac, to take the guesswork, and the disappointments, out of the equation. My only issue is that the use of shellac was employed widely in furniture after the pieces I wish to reproduce were originally made.
 
Thanks to everyone who has  responded to my posting.  If I make another one of these (and I intend to do just that), I will plan to rub out the finish in stages, starting with the secondary "top" as Ken suggests.  Since both the shellac and the lacquer seem to "soften up" from the rubbing out itself, I'll probably go back to the shellac next time.  As Fran noted, it's a wonderfully predictable and forgiving product.  I only used lacquer because I'm giving the table to my sister in Atlanta, where it will live in a front hallway.  I am tempted to use my random orbit sander with a polishing pad to complete this job, but I'm leery of switching horses in mid stream.  There's also the possibility of rubbing through - - I certainly don't want to go there!

Thanks again,

Bob
 
I don't think you'll have trouble with rubbing through this lacquer since the process you have gone through will have already rendered the surface almost perfectly flat. I don't know what equipment you have but I have found the variable settings of the Festool RO 150 6 inch sander to be pretty darned good for rubbing out finishes. The platin discs will get you close to the edge whereupon the lambswool (with whatever fine abrasive you use) will bring the finish up to a high gloss. Festool sells a porous sponge which velcros to the sander. It is excellent because it about an inch thick with a rounded edge. Use this with the Finesse and you can't do better, unless you have time to hand rub.
 
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