How to Coat Corner Bead With a Trowel: First-Coat Basics

Coating corner bead with a trowel comes down to one idea: on the first coat the mud must be full, not perfect. A drywall finisher with 15 years of experience explains that passing over the bead again and again pulls the material out, so one loaded pass and a feathering pass are usually enough.

Choosing the trowel

The trowel used is a straight 13×5 in. model with a slight curve. Trowels on big box store shelves or online are often curved the other way. The presenter doesn't recommend them: they leave the mud out a little on corner bead, but he calls them a one-trick pony and not particularly user friendly. A knife can be used with a very similar technique, but he says he is a trowel guy.

Mud and loading

For the first coat the mud should be fairly thick and well mixed, with little porosity, so it goes on nicely and doesn't shrink too much. The easiest way for beginners is to load the trowel and run it along the bead, working up to just past the middle at a comfortable working height. Normally he puts a blob closer to the front of the trowel and arcs the stroke to load the edge of the bead full. Arcing the wrong way puts a lot of mud on the edge.

Feathering and filling

The edge is feathered by pushing on it. A knife does the same by bending the blade, leaving a perfectly feathered edge. A corner bead is just filling point A to point B. The bead has a nosing that flares up, and that is what lets the mud cover the flange if the bead is installed properly. The first pass aims to clear mud off the nosing. Before going up to the ceiling he often makes sure the top edge of the trowel is clean so he doesn't put goobs on it.

Obstacles

With electrical boxes in the way, you work around them and try not to fill the boxes completely, though some mud gets in. He says a trowel is hard to use on things like this, so he often doesn't bother, and a knife comes in handy. More complicated bead work is done the same way on both sides, pushing on one side first and then lightly on the other. Anything that isn't perfect will sand flat and get a smooth second coat.