Creating clean transitions
The color separation for the cold foil should be created as a spot color channel and saved in TIFF format. A precise clipping path should be used when doing so in order to guarantee a clean transition between the foiled and foil-free areas.
Increasing the contrast
The color value of the foil reduces contrasts and lessens the spatial effect. This can be compensated for by altering the color composition of the overprinted design. The color value of silver foil contains high proportions of cyan and black. These color components should be reduced accordingly, and the other process colors increased.
If there are light areas where the foil is not omitted, then these areas of the foil should not remain unprinted. A more realistic rendition of light can be achieved by using 10% of a process color.
When light-colored foiled areas border dark printed areas, registration inaccuracies can become visible. This can be avoided by enlarging the color channel of the foil by one pixel. In Photoshop® this means creating a selection that is one pixel larger than the masked object.
Designs containing large proportions of black will appear more vibrant by producing the black from primary colors rather than using the process color black. In the case of grayscale images, a deeper black can be obtained by adding a cyan layer underneath.
Simulating cold foils on the monitor
It is not easy to picture how cold foil effects will appear. Sometimes the effect is difficult to predict and surprising. You can partially simulate the cold foil usage on the monitor by selecting a gray value of approx. 30 to 40% in the spot color channel options.