Where I stop and hand you off on finishing
Okay. Shelf is sanded, it's smooth, you've probably touched it more times than you needed to just because it feels good now. That's the whole point of the last lesson, so I'm glad if that's where you're at.
Here's where I need to be honest with you. Finishing is not my strong suit. Stains and varnishes give me fits. I get drips, I get uneven color, I get brush marks that show up under the kitchen light three days later when I thought everything looked fine in the garage. I've made peace with it, mostly, but I'm not going to stand up here and teach you something I'm genuinely bad at. That's not fair to you and it's not fair to the finish.
So this lesson is short. It's me telling you what I know, what I don't, and where to go from here.
What I can tell you
If you want to just protect the wood without changing the look much, a simple wipe-on poly or a Danish oil is about as forgiving as finishing gets. You put it on with a rag, not a brush, which cuts way down on the drip problem I just mentioned. You let it sit a few minutes, you wipe off the extra, and you let it dry. Do this outside or in the garage with the door open. The fumes are real, not dangerous in small doses with ventilation, but you don't want to be breathing that in a closed room, and you definitely don't want it near a pilot light or anything with a flame.
If you want color, a wood stain goes on before any topcoat, always. Test it on a scrap piece first, from the same board if you can, because pine takes stain unevenly and you'll want to see that surprise on a scrap and not on the shelf. This is the same reason I tell people to buy their lumber a few days before they cut it and let it sit in the garage. Our air out here is so dry the wood's still moving even after it's cut and sanded, and stain will show you every bit of that unevenness if you don't test first.
Two light coats beat one heavy one, on stain or topcoat both. That's the one piece of advice I'm confident handing you, because it's the one thing that's true no matter whose finish you're using.
Let it cure fully before you hang it. Dry to the touch isn't the same as cured. Give it the time the can tells you, and then give it a little more, because our dry air helps it dry fast on the surface and fools you into thinking it's further along than it is underneath.
What I can't tell you
Which specific product to buy. How to get a perfectly even coat with a brush. How to fix a drip once it's already tacky. I don't have good answers for any of that, and I'd rather send you to someone who does than make something up that sounds confident and isn't.
The folks at the hardware store paint counter are usually solid on this, better than me honestly. There's also a finishing class that comes around here sometimes, a few times a year, taught by someone who actually knows what she's doing with a brush. If sanding was the part that made you slow down and pay attention to your project, finishing is where that same patience pays off, I just can't be the one walking you through the fine points of it.
I will say this. Look at your project before you put anything on it. Check the surface for anything you missed, any leftover pencil marks, any spot you sanded past a screw head without noticing. I cut into a board once without checking it first and there was a screw hiding right where my saw blade went. Nicked the blade bad enough I still have it, hanging on the wall of the garage, not because I like looking at a ruined blade but because it reminds me to actually look at what I'm about to work on instead of assuming I already know what's there. Same idea applies here. Look before you finish, not just before you cut.
The opinion I'll stand behind
Sanding is where the project actually gets made, not finishing. Most people rush sanding to get to the finish faster, and I think that's backwards. A great finish on a poorly sanded shelf still feels rough under a coat of poly. A so-so finish on a shelf that's been sanded slow and thorough still feels good in your hand. If you did the last lesson right, you're already most of the way to a shelf you'll be happy with, finish or no finish.
Not great, but it held, that's been my standard for a long time. Your finish doesn't have to be perfect. It has to protect the wood and it has to be something you're willing to live with on your wall.
Before next time
Pick up whatever finish you're going to use, wipe-on poly is the easiest place to start if you're not sure, and test it on a scrap of the same wood before it touches your shelf. We'll talk about hanging hardware next, which is the part I actually do know well.