How to Use Opacity Masks in Adobe Illustrator CS6
You can use masks to make more interesting artwork in Adobe Illustrator CS6. Create an opacity mask from the topmost object in a selection of objects or by drawing a mask on a single object. The mask uses the grayscale of the selected object as its opacity mask. Black areas are transparent; shades of gray are semitransparent, depending on the amount of gray; white areas are opaque.
To create an opacity mask, follow these steps:
Open the Transparency panel menu.
Make sure that the Blend Mode drop-down list is set to Normal.
Create a shape anywhere on the artboard or open a document that has artwork on it.
We’re using a circle, but the shape doesn’t matter. Make sure that the artwork has a fill. A solid color helps you see the effect.
Open the Symbols panel (choose Window→Symbols Panel) and drag a symbol to the artboard.
In this example, we’re using the drums symbol.
Using the Selection tool, enlarge your symbol so that it fills the shape.
Select both the symbol and the shape and then click the Make Mask button.
The symbol turns into a mask, showing varying levels of the underlying box of the newly created mask, depending on the original color value. To delete an opacity mask, click the Release button.
Click the right thumbnail (which represents the mask) in the Transparency panel, and a black border appears around it, indicating that it’s active. You can move the items on the mask or even create items to be added to the mask.
The mask works just like the regular artboard, except that anything done on the mask side is used only as an opacity mask. To work on the regular artboard, click the left thumbnail.