Anyone have a better trick for hiding kerf marks on curved trim?

The faceted look happens beacuse the kerfs on the back are spaced too far apart, leaving flat segments on the face that the light catches. Hot mud isn't the best choice here because it lacks the structural body to actually bridge those flats, and it tends to shrink just enugh to reveal the underlying geometry once it dries. If you want a true radius, you need to use a **long-board sander** or a flexible sanding strip that spans across the entire curve.

Instead of just filling the gaps, you should be focused on taking down the high points of those segments. A rigid sanding block won't work on a curve, so take a piece of flexible plastic or a thin strip of wood and adhesive-back sandpaper to create a custom sanding tool. This forces the sandpaper to follow the intended arc rather than dipping into the low spots. If the facets are realy deep, skip the mud and use a two-part wood filler or even Bondo. It won't shrink, and it sands much cleaner than drywall compound.

For future installs, the trick is to make your kerfs much shallower and significantly closer togehter. We’re talking maybe 1/8 inch apart. It takes longer at the saw, but it makes the wood behave like a noodle rather than a series of hinged plates. You can also spray the face of the board with warm water to help the fibers stretch without snapping.

If you're dealing with a really tight bullnose corner, sometimes it’s better to just use a piece of **PVC trim** for that specific section. You can hit it with a heat gun, and it’ll wrap around a corner with zero faceting. Then you just scarf-joint it back into your wood runs. But for what you've got now, sand those high spots, switch to a non-shrinking filler, and hit it with a high-build primer before your final coats of paint.

I didn't realize you coud use Bondo on baseboards. Does that stuff smell relly bad inside the house though? I'm trying to fix a similar spot and I'm worried about the fumes if I use it in a small hallway.

Also, with that warm water trick, do you just spray it on the front while you're bending it, or does it need to soak for a while? I'm always terrified of the wood snapping if I don't get the moisture level just right.

To the guy asking about Bondo—yeah, it stinks like crazy for a few hours. If you're in a tight hallway, grab some MH Ready Patch instead. It’s way tougher than mud, sands like a dream, and won't gas you out. Also, be careful with the water trick if you’re using MDF baseboards. If that stuff gets too wet, it’ll swell up like a sponge and you’ll have a permanent bump instead of a facet. I always use a pencil to scribble over the curve before sanding. It shows you exactly where the high spots are so you don't over-sand the middle of those flats.

Try the flashlight trick to see if you've actualy got it smooth. Lay a flashlight flat against the wall so the beam skims the curve. The shadows will show you every tiny flat spot you missed. If it's still looking jagged, I usally use a flexible sanding sponge. It lets you feel the transitions much better than a rigid block.

If you’ve got more of these to do, check out Flex Trim. It’s a rubbery moulding that bends around corners easily. It’s pricier than wood, but it saves you the trouble of kerf-cutting and mudding those tight bullnose corners.

I've had success using a guide coat to find those pesky flats. After your first round of sanding, lightly scribble all over the curve with a pencil or some chalk. When you hit it again with your sanding strip, the marks stay in the low spots and disappear on the high points. It’s a trick from auto body work that makes the geometry way easier to see than just relying on the afternoon sun.

Just be careful not to oversand the 'shoulders' of those segments. If you take too much off the edges of a flat, you'll just create a new, deeper flat spot.