Let me tell you-leaving lines with a corner trowel is one of the most frustrating things about DIY drywall work. I've been there: you finish a corner, step back, and see those ugly, streaky lines that make the whole thing look messy. But here's the good news: it's totally fixable, and it all comes down to three things-prep, technique, and patience. Let's break it down step by step.
First, start with the right joint compound consistency. If your compound is too thick, it'll clump on the trowel and leave lines as you pull it. If it's too runny, it'll drip and leave uneven spots. Aim for the texture of "soft sour cream"-smooth, spreadable, and not too heavy. I usually mix a little water into pre-mixed compound (start with a splash, stir well, and add more if needed) until it's just right. Test it by dipping the trowel in: it should stick to the blade without sliding off immediately, and spread easily when you press it to the wall.
Next, load the trowel correctly-less is more. I used to pile on compound thinking it would save time, but that's a surefire way to leave lines. Instead, scoop a small amount (about the size of your palm) onto the trowel. For inside corners, spread it evenly across both sides of the V-shape; for outside corners, focus on covering the corner bead without overloading the edges. Too much compound means you'll have to press harder to spread it, which creates ridges and lines. A thin, even layer lets the trowel glide instead of drag.
Now, the technique: angle and pressure are everything. For inside corners, hold the trowel so the V fits snugly against the corner (not too loose, not too tight) at a 45-degree angle to each wall. Start at the top and pull the trowel down in one slow, steady motion-no jerks, no stopping. Keep the pressure even across the entire blade; if you press harder on one side, you'll leave a lopsided line. For outside corners, hold the trowel so its flat edge follows the corner bead, and pull downward with light, consistent pressure-think of it like you're "ironing" the compound onto the bead, not scraping it.
Another pro trick: "feather" the edges. When you reach the bottom of the corner, lift the trowel slightly as you finish the stroke. This softens the edge of the compound so it blends into the wall, instead of leaving a hard line where the trowel stopped. I used to stop abruptly, and that's where those harsh lines came from-lifting gently fixes that in seconds.
And don't forget the second coat (and light sanding!). Even if your first pass looks good, a thin second coat is key to erasing any tiny lines you missed. Let the first coat dry completely (check the compound's label-usually 24 hours), then sand it very lightly with 120-grit sandpaper. Don't scrub-just dust off any rough spots. Then apply the second coat with the same slow, steady technique. The second coat fills in small lines and gives you that seamless, smooth finish.
Lastly, clean your trowel between coats. If dried compound builds up on the blade, it'll leave scratches or lines in the fresh compound. Wipe it off with a damp rag after every use, and if there's dried gunk, soak it in warm soapy water for 10 minutes to soften it before scrubbing. A clean trowel is a smooth trowel-simple as that.
It takes a little practice (my first few corners still had lines!), but once you nail the consistency, loading, and stroke, you'll be able to do corners that look like a pro did them-no lines, just smooth, crisp edges. Trust me, that "no-line" finish is worth the extra time to get the technique right!
