so i started a painting in photoshop, i have three layers, a background which is currently white and blank, a second layer which is my ground sketch and the top layer which is all color. My issue is that now that i have the top layer colored i want to add in a background. But only places where i have eraced mistakes show through to the background and i dont know how to make the rest of the "white" areas invisible or see through so that the background shows up... can anyone help with this? im sure its some simple layer option. (i also plan on deleting the sketch layer as i no longer need an outline).