Sanding through the grits, slower than you want to
Okay. Glue's cured, shelf is square, it survived overnight in the clamps. Now we sand.
I'll tell you 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 on the wall. I get it. But I feel like this is actually where the project gets made, more than the cutting, more than the glue-up. This is the part people are going to touch. Every time they run a hand across the top of that shelf for the next ten years, they're feeling what you do today. So we're going 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 skip 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 dust.
- Good light. Actual good light, not the one dim bulb over your bench. You need to see the surface at an angle to catch 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 show up 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 checking for glue squeeze-out that's gone hard, any spots where the joint isn't quite flush, tool marks left over 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're at 220 you're not really removing material anymore, you're polishing what's already there.
The thing is, most people stop at 120 or maybe 150 because it already feels smooth to their hand. It's not. Your hand is a bad judge of smooth when you're in a hurry. Slow down, do the last grit, 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 of it 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 that 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 out of a factory. But you don't have to chase perfect. A little unevenness in the wood 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 that people will bump into with their hip walking by are going to get bumped and rounded eventually anyway, might as well do it on purpose and evenly.
If you're sanding indoors, especially in a garage that isn't super 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 get in 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's sitting slightly proud will chew up your sandpaper fast and won't fix the actual problem, which is 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 going to see. Next time we talk finish, and I'll be honest with you now, that's the part of this whole process I'm worst at. I'll tell you what I know and where to go looking for better advice than mine.