Sanding through the grits, slower than you want to
Glue's cured, the shelf is square, it made it through the night in the clamps. Now we sand.
I'll say it up front, this is the lesson people want to rush. You've got a shelf-shaped object sitting on your bench and you want it up on the wall. I understand. But this is where the project really gets made, more than the cutting, more than the glue-up. This is the part people are going to touch. Every time somebody runs a hand across the top of that shelf for the next ten years, they're feeling what you do today. So we go slow.
What you need
- Sandpaper in a few grits. 120, 150, 220 is a good progression for pine. If your box only came with two grits, that's fine too, just don't jump straight from rough to super fine.
- A sanding block, or just a scrap of wood wrapped in the paper. Bare-hand sanding works, but you'll round over edges you didn't mean to round.
- A rag or shop vac for the dust.
- Good light. Actual good light, not the one dim bulb over your bench. You need to catch the surface at an angle to see what you're missing.
The order of operations
Start at 120 grit. Go over every surface, every edge, with the grain, not across it. Cross-grain scratches stand out like a sore thumb once you finish the wood, even if they look fine dry.
Don't linger in one spot. Keep the block moving, even pressure, and cover the whole surface before you go back over anything twice.
Once you've done a full pass at 120, wipe the dust off and look at it in that angled light. You're hunting for glue squeeze-out that's gone hard, any spot where the joint isn't quite flush, tool marks left from cutting. Deal with those now, still at 120, before you move up.
Then go to 150. Same thing, whole surface, with the grain. Then 220. By the time you reach 220 you're not really removing material anymore, you're polishing what's already there.
Most people stop at 120 or maybe 150 because it already feels smooth to the hand. It's not. Your hand is a poor judge of smooth when you're in a hurry. Slow down, do the last grit, and you'll feel the difference, and so will everybody who ever leans on that shelf.
A story about a crooked nail
I built a bookcase a while back for my friend Alexandria's kids, and near the end her youngest wanted to help. So I let her hammer in the last nail. It went in crooked, angled off to one side, and you could tell right away it wasn't going to sit flush no matter what.
I started to pull it and redo it and Alexandria stopped me. Said leave it. So we left it. That bookcase has been in their house for years now, and every time I see it I look for that one crooked nail before anything else.
I bring it up here because sanding is where a lot of people try to erase every trace that a person made the thing. And you can, mostly. You can sand a shelf until it looks like it came off a factory line. But you don't have to chase perfect. A little unevenness in the grain, a small mark from a clamp, that's not a flaw you failed to fix. That's just a shelf somebody built by hand instead of one that got stamped out somewhere.
Sand it well. Don't sand it into having no story.
A few things to watch for
Sand your edges and corners a little softer than you think you need to. Sharp square edges on a shelf people will bump with their hip walking by are going to get knocked and rounded eventually anyway, so you might as well do it on purpose and evenly.
If you're sanding indoors, especially in a garage that isn't well ventilated, wear a dust mask. Fine wood dust in your lungs isn't something you feel right away, it's something that adds up over years of doing this, so build the habit now, even on a small project like this one.
Watch your screw heads if you countersunk them. Sanding hard over a screw head that sits slightly proud will chew up your sandpaper fast and won't fix the real problem, which is that the screw needs to sit lower.
Before next time
Get all the way through 220 on every surface before you stop, even the underside nobody's ever going to see. Next time we talk finish, and I'll tell you straight now, that's the part of this whole process I'm worst at. I'll share what I know and point you toward better advice than mine.