Combine to Layer is a tool which gives you the control and flexibility to combine layers at different tonal percentages. There are two reasons for doing this; to reduce the number of colours in a design, and to adjust the look of a design. In addition, smooth continuous tones can be created to improve the balance between overprinting layers in a separation. Layers which are being edited are previewed in the Design Window in real time, letting you apply the changes only when you are happy with the overall results.
How to use Combine to Layer
Combine to layer can be used in various ways, such as:
- Adding the information from two or more layers together. This article explains how.
- Balancing layers which overprint by taking the information from one layer away from another layer. Click here to learn more.
- Adding the information from some layers while taking the information away from other layers at the same time.
- Combining textures and tones to develop textures. Click here to learn more.
- Adjusting the tonal levels of layers to create smoother fall on areas and better separations. Click here to learn more.
With the many functions of the Combine to Layer Window comes many different workflows. To get you up and running with using this tool, this article will focus on the basic principles of reducing the number of layers in a document by merging information from other separated layers in the document onto one layer.
Note: If you want to view the overall design alongside the layer you are editing, use the Split Views feature.
Surfaces
In this example, the design is currently made up of 6 layers. 
However, we should assume that for production we can use a maximum of 4 layers. In this case, the bottom two layers, which are creating the effect of the bevelled edge, can be built into the other 4 layers. The movie below demonstrates how:
Note: To view the above movie in a larger frame, hold down ^ (control key) on your keyboard and click on the movie. Select 'Open Video in New Tab' from the menu which appears.
Textiles
In this example, the design is made up of nine layers:
Note: To view the above movie in a larger frame, hold down ^ (control key) on your keyboard and click on the movie. Select 'Open Video in New Tab' from the menu which appears.
Wallcoverings
In this example, the design is currently made up of 4 layers. Layer 4 has a different transparency to the other layers, creating an opaque white effect over some of the other layers.
We can save the cost of engraving layer 4 by building its effect into layers 1 and 2. The movie below shows us how:
Troubleshooting Combine to Layer
If Combine to Layer is not working as expected, you may have forgotten to press 'Make' at the bottom window first. Therefore, activate the layer you want to edit (click on its pencil icon in the Layers Palette) and then click the Make button in the Combine to Layer Window. A preview icon will appear on the layer chip in the Layers Palette.
Also check that no other layers are active. If more than one layer is active in the Layers Palette, the Combine to Layer Window will be empty.
Use the keyboard shortcut ⌘D to ensure no hidden selections are in the file.