Color, Underbase, and Flash...

When deciding on colors for your shirts there are many factors to consider.

1. What color shirt?

2. What color/colors of ink?

3. Will it require an underbase?

4. Will any of the colors require a flash?

In order to understand the process here you need to remember a few things. You cannot print ink onto wet ink, our ink only cures when its surface temprature reaches 350 for 1 minute. You can partially cure our ink so that is can be printed on top of with a flash unit.


One difficult part of the process known as screen printing, is printing light colors on dark t-shirts. There are a few different ways of making the light print stand out and look great on darker colored t-shirts. One of the ways to do this is by adding an actual layer of clean printing surface underneath of the design. This is called an “under base” and it is from this that the term “under basing” is derived.

An under base is usually done with white ink. The reason for this is that the white provide a very neutral color for the other ink colors to be printed on top of. It is also the lightest color so it provides better results on darker shirts. The way the process works is that the screen printer will print a wide layer of ink underneath every color in the design. This provides a base canvas for the rest of the colors to then be printed on top of. That way it is almost like printing on white shirts instead of darker shirts.


A flash is the term for partially curing a layer of ink before adding a second layer on top of it.

I.E. We would print a white underbase first. Then move the pallet that the shirt is on under a flash unit for 15-30 seconds. (The flash unit is simply a heating element that partially cures the ink.) Then we can print a second color.

Lets look at the shirt color vs. ink color first for a 1 color job. This job is a red ink on an athletic heather shirt. For this shirt color and ink color there is not need to use an underbase as this is a dark color ink going onto a light shirt. Had this shirt been a dark grey, then we would have printed a white underbase, flashed and then printed the red.

In this example we used an underbase, then two colors on top of that underbase to give us a three color print.

For this job we printed white, flashed, then printed white again, flashed then printed the red.

For this job we printed silver metallic, flashed and then printed red. Had we not printed the silver metallic the red would be much darker and not stand out the same.

So as you can see flashing and underbases are part of just about any job that is not one color.

Look for our next Screen Printing blog.

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