The first step to getting sharp lines is all about preparation. Before you start applying joint compound, make sure the corner is clean and smooth. Remove any dust, loose paper, or debris from the drywall. If there are any small imperfections in the corner, you can use a utility knife to trim or smooth them out a bit.
When applying the joint compound, use a light hand at first. Load a small amount of compound onto the trowel. For inside corners, hold the V - shaped trowel at about a 45 - degree angle to each wall and slowly pull it down the corner, applying even pressure. This will ensure the compound spreads evenly. If you see any gaps or if the compound seems to be piling up in some areas, stop and adjust. You can go back with a bit more compound to fill the gaps or use the trowel to smooth out the excess.
For outside corners, make sure you have a proper corner bead installed. Hold the outside corner trowel so that its flat edge follows the bead. Press the trowel firmly against the bead as you pull it along, spreading the compound evenly over the bead and sealing the edges.
Another important thing is to work in layers. Don't try to get the perfect sharp line in one go. Let the first coat of compound dry completely. Then, sand it lightly with fine - grit sandpaper. This will smooth out any rough spots. After sanding, apply a second coat of compound with the trowel. This second pass is where you can really focus on getting that sharp, clean line. Take your time, and be patient. With a bit of practice, you'll be able to achieve those sharp lines that make your drywall work look professional.
