Love the grit of your sandpaper, as it is critical in the finishing process. If you follow the blog, you know I prefer to use waterborne coatings; and sanding is critical, because these coatings cause the grain to raise. A good sanding will knock down the raised grain, preparing the road for a wonderfully smooth finish.
In this blog entry you get two for the price of one: A tip to help you keep track of your coating’s life, and something to help you get a nice, smooth finish.
In a recent article I showed how I go about prepping the legs to seal the wood for the stand-up desk, and to impart a wonderful reddish tint to the walnut by using a waterborne garnet shellac from Target Coatings, UltraSeal-WB. This product, like most waterborne coatings, raises the grain; as a result, light sanding is required to ensure a nice, smooth finish. I first tried the shellac on a test leg, to make sure it was still in satisfactory condition, as the can was close to one year old. This brings me to the following Tip-of-the-Day:
Tip for the use of coatings: Using permanent marker, always mark on the lid the date on which you first opened the container. Exposure to air is many times responsible for the premature expiration of perfectly good coating materials. The shellac was getting close to the first-year anniversary of the UltraSeal-WB:
As the application of the UltraSeal-WB went well on the tests on the spare leg I made, I proceeded to apply the initial seal coat to all four legs, using a lint-free rag:
It was apparent on inspection that I would need to sand, as the first application of shellac raised the grain significantly – the wood surface felt almost as rough as 150-grit sandpaper:
I proceeded to sand all surfaces on the legs with 3M’s 216U Fre-Cut™ Gold 600-grit sandpaper, which I mentioned in an earlier blog entry titled Sanding — gotta love it. Viewing the results of sanding at a low angle reflects the light nicely, an indication that the wood surface is now smooth:
Using 600-grit 216U sandpaper allows sanding of critical areas, such as the bevel on the legs – I would normally worry about sanding away too much of the thin layer of shellac at the corners, and rounding the corners, but not with this sandpaper:
Now I can continue the finishing process: I will give a second application of the garnet shellac to the walnut legs. The white oak, high in tannin content, will receive one or two coats of alcohol-based shellac, to seal the surface. Note: Avoid high-pH waterborne coatings directly on the raw wood surface of high-tannin woods like red and white oak, as pinholing and bridging are likely to develop; that would make it difficult to get a nice, smooth finish.
Following all these preliminary finishing steps I will do a dry fit, in preparation for the glue-up. The glue-up will include drawboring of the mortise & tenon joinery. Then, and only then, will the desk be ready for the waterborne topcoat, Emtech 2000wvx alkyd varnish; I will do that in the finishing room.
— Al Navas