M
McRabbet
Many of you may have seen my earlier thread "Unique Countertop Commission" that described a beautiful solid Bubinga countertop I built for a client here in Hendersonville. After the installation was completed, I gave the top a final coat of Rockhard Tabletop Varnish and snapped some final pictures, like this one: 
You can see the nice glossy finish, but something more ominous shows if you look more closely, especially around where the overhead light is reflected. I came back five days later to check the finish and to caulk around the angle brackets and noticed numerous imperfections in the varnish -- often called "pimples" in the literatures -- I call them "Nits". The client was not pleased with this surface, nor was I -- and his wife said she would prefer a satin finish. Here is a close-up after I discovered what the problem really was and what caused it. 
The nits were not embedded bubbles as I first suspected; they were small solidified particles of varnish that got into the final coat from the varnish brush -- I had picked up one of my very best brushes for this final coat and it had not been cleaned properly -- a fine film of varnish remained on many bristles and they broke off during that application as the brush flexed and laid down in the application. Ugh! My fault and now I had to figure out how to remove them without damaging the finish and leaving scads of dust all over the clients now furnished new home!
I used 320 grit paper in my RO sander with a vacuum hooked to the exhaust port. The Shop Vac had a Drywall Filter Bag installed so nothing could pass through. It took about 2-1/2 hours of patient sanding (8 disks of 320 grit were used) got the "Nits" sanded down to the final finish layer, followed by re-sanding with 400 grit, 600 grit and then 800 grit paper. Here is the result:
A beautiful, blemish-free surface!
Thank goodness they wanted a satin finish! I was prepared to rub out this surface back to a high gloss -- I had 1000, 1200, 1500 grit papers, plus 2F and 4F pumice, rottenstone and furniture wax waiting in the wings! Needless to say, I'll always check my varnish brush whenever I pick it up (I've since re-cleaned that contaminated $20 brush and combed out all of the remaining varnish it contained!)
Rob
You can see the nice glossy finish, but something more ominous shows if you look more closely, especially around where the overhead light is reflected. I came back five days later to check the finish and to caulk around the angle brackets and noticed numerous imperfections in the varnish -- often called "pimples" in the literatures -- I call them "Nits". The client was not pleased with this surface, nor was I -- and his wife said she would prefer a satin finish. Here is a close-up after I discovered what the problem really was and what caused it. 
The nits were not embedded bubbles as I first suspected; they were small solidified particles of varnish that got into the final coat from the varnish brush -- I had picked up one of my very best brushes for this final coat and it had not been cleaned properly -- a fine film of varnish remained on many bristles and they broke off during that application as the brush flexed and laid down in the application. Ugh! My fault and now I had to figure out how to remove them without damaging the finish and leaving scads of dust all over the clients now furnished new home!I used 320 grit paper in my RO sander with a vacuum hooked to the exhaust port. The Shop Vac had a Drywall Filter Bag installed so nothing could pass through. It took about 2-1/2 hours of patient sanding (8 disks of 320 grit were used) got the "Nits" sanded down to the final finish layer, followed by re-sanding with 400 grit, 600 grit and then 800 grit paper. Here is the result:
A beautiful, blemish-free surface! Thank goodness they wanted a satin finish! I was prepared to rub out this surface back to a high gloss -- I had 1000, 1200, 1500 grit papers, plus 2F and 4F pumice, rottenstone and furniture wax waiting in the wings! Needless to say, I'll always check my varnish brush whenever I pick it up (I've since re-cleaned that contaminated $20 brush and combed out all of the remaining varnish it contained!)
Rob
