I’m finishing a large table top with Waterlox Original varnish (after a sealer coat of unwaxed shellac). It’s been sitting for a couple of weeks. When I start to sand it with 320 open grit sandpaper ( in preparation for additional coats), after a couple of strokes, the sandpaper starts to clog up & little, thin rolls of material begin to form. Since that didn’t happen on prior sandings, I’m wondering if the varnish was getting old when I applied the last coats. Should I try wet sanding with water & dish detergent? Would it work better to use some mineral spirits as the lubricant, instead?
The other problem that I’ve had, leading up to this one, is that the finish wasn’t building up in some of the low spots in the grain (although, I sanded to 220 & thought it was really smooth before applying any finish) or in the slight spaces between some of the boards where the joint glue-ups were not perfect (there are 122 pieces in this 5′ X 10′, eliptical table top). So, as I added coats & then sanded, I guess, I was sanding “the mountain tops” off and then building them up, again. I’ve attacked it with 0000 steel wool, to get into “the valleys” which has helped a bit. I’ve attacked the spaces between boards with steel wool & even tried the edge of folded sandpaper in the spaces, with little success. I’m to the point of giving up on getting those spots as nice as the rest of it. Any suggestions?
I know this is long. Thanks for taking your time & for any ideas you may have.
Morty
Replies
Well, how long has it been since you first opened the can? When you mention previous sandings are you referring to previous coats on the same table from the same can? Waterlox ought to sand to powder after a couple of weeks.
I don't like using real steel wool on intermediate coats. It can leave shards, and 0000 is really too fine to add much tooth for varnish to grab. . If you do want to get valleys, then this is the place for synthetic steel wool (3-M pads or the like.) But using the flexible abrasive instead of sandpaper on a sanding block if done to any extent, defeats the purpose of using the finish to fill surface defects. But, especially with a relatively low solids finish such as the Waterlox Original/Sealer isn't a very efficient way of accomplishing that--it would take very many coats.
You can use lubricated paper. It is messy, and without a fair bit of experience you can get carried away before you know it since the impact of the sanding isn't nearly so visible. Stearated paper works a lot better than open coat at not clogging.
synthetic steel wool& stearated sandpaper
Hi Steve,
Thanks for your reply. Did you mean "if you want to get INTO THE valleys", so I can build them up? Will stearated sandpaper interfere with the bonding of additional coats?
Morty
Yes, into valleys would be right. But the reason for that is just to add tooth for varnish to adhere better. Non-poly varnishes such as Waterlox don't need much tooth. The goal is to remove as littleas possible from the valleys while removing the mountain tops.
Some waterborne finishes have suggested not using stearated papers, but with oil based finishes it isn't a problem. What ever paper you use you would still wipe down the surface with naphtha or mineral spirits.
I'm using Waterlox Original for my finish - 2-3 wipe on coats between sandings.
I've been unable to find "stearated" sandpaper. But, the flat sanding is working out all right. It's slow, since I have to use a soft bench brush to remove the powder, after every few strokes, as it starts to form corns. Then, I've been following with synthetic steel wool and "sandblaster" (without a sanding block), to get into the valleys. My question is this. After I've flat sanded & synthetic steel wooled it; the surface is all pretty "flat" looking. But, after 1/2 hour or so, some areas start to look shiny, again. This increases with time. What is happening & will this shininess interfere with the bonding of the next coat?
I really appreciate your responses.
Morty
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