|Here is part two of a three-part
series on sanding. If you don't want to waste a lot of time sanding, then you
need to understand the big picture. I used to think of sanding as a one-step
process -- just getting the wood ready for a finish. But now I like to think of
it as two separate steps.
FIRST STEP. The goal of the first step is simple: sand out all of the
blemishes. By blemishes I mean any deep or cross grain scratches as well as
nicks and dents. This step also includes any burns and layout marks. The first
step should be tackled with the coarsest grit you plan to use. Whether it's 100
or 150, don't switch to a finer grit until all the blemishes are gone.
Switching too early just means you'll spend more time sanding.
SECOND STEP. When all of the blemishes have been removed, it's time to
sand with finer grits. The goal is to make all of the scratches left by the
previous sandings finer and finer so they won't be visible after the finish is
Move to the next grit when you sanded out all the scratches from the previous
grit. (Good lighting and close inspections are important here.) And don't skip
more than one grit. In the long run you'll spend more time sanding -- not less.
EXCEPTIONS TO THESE RULES. When sanding, it's a good idea to keep the big
picture in mind. But there are times when it's more efficient to bend the rules
a little bit.
One rule you'll hear often is to only sand with the grain. But some times
there's a lot of wood to be removed, like on an edge-glued panel with lots of
ridges. In these situations, sanding with the grain has some drawbacks. It's
slow. And there's also a tendency to create dips and valleys across the panel.
So when there's a lot of wood to be removed, I'll start by sanding across the
grain first with my portable belt sander. Don't sand any more than needed.
Remember, you'll have to sand out the cross grain scratches by going back and
sanding with the grain.
END GRAIN. There's another rule I bend a little. It has to do with end
grain. Instead of starting with a coarse grit like 100, I sand with a medium
grit like 120 or 150. This way, I'll have to spend more time on the initial
sanding, but I think it's faster in the long run. Here's why.
Coarse grits are good for removing nicks and really deep scratches, but they
create deep scratches themselves that have to be sanded out with finer grits.
The problem is end grain is harder than face grain. So the scratches left by
the sandpaper are harder to sand out.
WORN PAPER. This is a rule I always follow. I change my paper often.
It's tempting to keep the paper on for just a little longer because "it's
just going to sand finer anyway." But that's not how sandpaper works. As
the paper gets worn, some particles may be smaller. But they're also becoming
dull. So instead of finer and finer scratches, what you end up doing is
polishing or burnishing the wood instead.
Go to Tip #54