So, how do you know where to lay the tape and make the line? First off, you need painters tape...frog tape to be exact. The blue tape just will not do the trick for this project. In our home, we have what are called bullnose corners, but they come to a point at the bottom. At the bottom, it is easy to form the line between rooms. Then, we just selected the inside of the round point and taped. Sounds easy...but it really is not. It is has to be a perfect straight line or it will just look awful. The tape needs to be applied from the ceiling down in most cases.
Once the line in taped, it is time to paint. Paint away. Once both coats have been applied (let's be honest, the "2 coat paint" never seems to be quite good enough), the tape should be removed. I have found the quicker the tape comes off, the better.
And here is the result form our painting project. Kitchen: Valspar Burnt Caramel (from Lowes) and the family room: Sherwin Williams Latte.
