To perform an eye mask test, engineers used to draw a mask on the display of an analog oscilloscope with a grease pencil. Next, they had to trigger the oscilloscope with clock signal, turn up the ...

To form the "mask," use a liquid liner to draw on top of the gold shadow and along your crease. Revlon's ColorStay Triple Edge Liquid Eye Pen is shaped like a, well, pen so you can literally draw ...