*
greetings
we are having problems wet sanding a piano primed and topcoated with an ebony lacquer. This piano is going high gloss and we seem to be building “corns” rather instantly on the paper. There is a good amount of surface detritus and orange peel to sand out for a glasslike surface and we have been going through a good amount of wet/dry sandpaper. We have also used a silicon wet disc on an orbital sander both wet and dry with the same results (corn buildup). What are the gurus out there suggestions on paper, lubricants and overall techniques. We are using
400-600-800-1000-1200 grits in order then wheeling the finish out with a 3 step compounding/polishing finish. thanks in advance
Robert Mansfield
Discussion Forum
Get It All!
UNLIMITED Membership is like taking a master class in woodworking for less than $10 a month.
Start Your Free TrialCategories
Discussion Forum
Digital Plans Library
Member exclusive! – Plans for everyone – from beginners to experts – right at your fingertips.
Highlights
-
Shape Your Skills
when you sign up for our emails
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. -
Shop Talk Live Podcast -
Our favorite articles and videos -
E-Learning Courses from Fine Woodworking
-
-
Replies
*
Robert,
It's probably still too green, especially if it's nitro and not acrylic lacquer. Particularly if it was shot heavy and/or insufficient flash time, it can take a few weeks for the solvent to creep through the layers. Keep some air moving across it. The olde-fashioned boys would wait 3-6 months before beginning buff-out. Stick your nose into the finish; if you can smell it, leave it awhile. Oftentimes when I've been in a hurry to get a project done I'll cut the top open with the 400, let it sit another day or two, then the 600, another day or more, and so on through the higher grits and compounds. Always use wet, a TINY amount of dishwashing detergent in a bucket of water will minimize build-up on the sandpaper, but better is to wait, if you can.
*If you are still getting corning, it would seem that your finish isn't cured out yet. If you put on too-heavy coats too close together, the finish could take a couple of weeks to cure out, more in cool temperatures. I try to allow 30 days before rubbing out, whenever I can arrange it.There could also be a problem with the formulation of the lacquer itself. I once got some with too much ethylene glycol in it, and I don't know whether it ever would have dried. We had to refinish a LOT of work.Your sanding & polishing schedule sounds fine. Water with a couple of drops of dishwashing detergent is the most aggressive cutting lubricant I've found,and is easy to clean up. Mineral spirits is less aggressive, and you can mix it with Naptha to speed up the drying rate.If you haven't tried the foam compounding and polishing wheels, by all means do. They seem both faster and more controllable.
*What/whose lacquer and color coats are you using? If perchance its the stuff made for the manufacturer (like Steinway), it may be formulated for hot spray application and will have copious amounts of MAK and other high boiling solvents (they act as retarders).Jeff Jewitt
This forum post is now archived. Commenting has been disabled