Striking a balance between vibrant colors and subtle details requires a careful approach to creating separations. Trimingham describes his favorite method in this month's column.
The ink-fall-off point is a specific percentage of underbase where the overprinted ink changes hue from its main color. It may not be an obvious spot and may encompass a range of values, but this range is where an artist can create some very interesting effects by using a color that barely appears on a dark shirt to develop drama in the shadows.
Another equally critical element in this process of testing the underbase and top color overprint is to determine at what percentage the underbase color still shows through the top color’s halftone. This issue is a common cause of on-press failures and shirt rejections from clients. The last thing a printer wants is for the underbase to show where it shouldn’t.
Using a simple gradient overlay is a quick way to determine the fall-off point for the inkset in use (Figure 3). Test several of the inks in a set to make sure the properties are consistent from ink to ink. Don’t assume that the red has the same opacity as the blue, only to find out on press that it doesn’t even show up on the black shirt and, as a result, you have to remake two screens in a mad rush.
Once you determine and record the fall-off points, you can quickly prepare art without a lot of worry about how it will reproduce on press. One key is to make sure that the final screens, films, mesh, and inks share all the same values with the test. Things like screen tension and mesh count can make a big difference in the amount of ink that is laid onto the shirt and how opaque the colors appear.
Separating art for underbase fall-off and deep shadows
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