Explore how creative uses of underbases can produce some knockout designs.
The concept of this special effect is to create an image with real dimension that invites the viewer to feel the surface of the garment and see the image pop off of the shirt in the right areas. This effect is achieved through the skillful use of modified ink that has a blowing agent added to the mix. A blowing agent is a compound that releases gas upon being heated. The gas that forms inside the heating ink causes the ink to expand upward in a domelike shape. Inks of this type are commonly referred to as puff inks, but I don't recommend using standard puff ink out of the can for this process. You'll achieve the best results when you mix a small amount of puff additive into an ink. Doing so allows you to control the amount of puff reaction.
I normally look at the manufacturer's specs on the puff additive and add between 5-10% so the ink won't puff too much. Another way to improve this process is to mix a stretch additive into the ink. The stretch additive gives the ink a smoother surface than regular puff ink will and maintains more detail of the halftones or line work that you print on top of the expanding underbase. I usually add 10-15% stretch to my ink for this method to help prevent loss of detail.
White is the most common color for an expanding underbase ink. In some cases, you may want to use a colored expanding ink to prevent the overprint from lightening too much. All puff-ink underbases will generally lighten overprinted colors to some degree. You can control the amount by managing the ink's expansion and keeping the ink film's surface smoother. The change you'll see won't necessarily a bad one. It'll often give the print a really cool, slightly worn look that is very popular.
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