How to Use the Erase to History Option in Photoshop CS6
When using Adobe Photoshop Creative Suite 6, use the Eraser with the Erase to History option when a portion of an earlier state or snapshot contains information that you want to include in an image that you’ve extensively edited.
To erase and restore to a portion of an earlier state or snapshot, just follow these steps:
In the History panel, click in the far-left column of the state or snapshot that you want to use as the source for the Eraser tool with the Erase to History option.
A brush icon appears to the left of the state’s listing in the History panel, indicating that Photoshop will use this state as the source for the Eraser tool with the Erase to History option.
Select the Eraser tool.
You can also press the E key to access the tool.
Select the Erase to History option on the Options bar.
Select any other Eraser tool options that you want to use, such as Brush size and type, Mode, Opacity and Flow percentages, or Airbrush.
The Mode options include a Brush, Pencil, or Block tip for your brush.
Select your desired layer in the Layers panel and, in the History panel, select the state that you want to erase to.
Drag your eraser on the portion of the image you want to erase.
Photoshop removes the image in the layer and replaces it with the image in the state that you specified as the source in Step 1.
You can convert the Eraser tool so that it temporarily uses the Erase to History option by holding down the Alt key (Option key on the Mac) while you erase or paint.