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Printing A White Under Base On Black Or Dark Garments
This article is intended to introduce you to white under base printing. This can be a very technical process and requires that you are familiar with the technique. White under base screens are often burned on 110 mesh. If you are printing fine detail or halftones on top of the white under base, you will need to use a higher mesh count for the under base in order to provide a smoother more consistent surface. Printing halftones or fine detail on a rough under base will produce poor print quality. Subsequent colors may require a higher mesh count depending on the inks you are using and your artwork. High quality, high opacity inks are necessary for obtaining great results easily.
The under base will actually fill the knit some and keep the colored ink to be printed on top from soaking into the fabric of the shirt and thus losing its intensity as well as its coverage ability. It is somewhat like a primer when painting a house. The primer seals the surface and presents a good surface to paint onto.
In most cases, when printing dark garments, you will want to print a white under base. Some plastisol inks are made to be "high opacity". These "HO" inks are intended to be printed on a dark garment without the need for a white under base. Many of these inks are great and work very well. Sometimes it will be necessary to do a hit-flash-hit in order to achieve the coverage you desire. But most will work well using 110 mesh stretched tight. And as always, you would want to avoid the hit-flash-hit to keep production time at a minimum. Wilflex makes great high opacity inks for dark garments. Most of their inks will cover well just using 110 mesh.
Heat buildup is a problem that has to be resolved with cool down stations. If you are printing with a fixed pallet and print head, you will need to let the pallet cool between prints. This is very important. And be sure that your flash dryer is not heating the screen above it. With a fixed pallet and print head you will need to set the flash dryer so that it flashes the under base quickly thus limiting heat buildup time for the screen and pallet. It is best to use a rotary press for this or any multi color printing with a flash cure.
Creating your artwork for multi color jobs on a white under base can be difficult. I highly recommend letting someone do this for you if you have never done it before. You will be able to learn from the film and setting up on the press all the "how's and why's". If you are just printing 1 color on the under base, then you should be able to set it up yourself.
The artwork for a 1 color print with an under base should be choked some. That is to say that the color over printing the white under base should over print the white under base by at least � point. This will make it easier to print and can compensate some for ink or shirt shrinkage. So for the most part, the artwork for the white under base is the same as the color to be printed onto it but just slightly smaller in overall size unless your art calls for white outlines. Then you might be printing inside the white under base and following up at the end with a white highlight printer to whiten these areas.
Whether or not you will need to print a white under base will depend on your particular printing situation, inks and artwork. Using high quality inks that may cost more but eliminate the need for a white under base can save a lot of labor costs.
For more detailed instructions and explanations of this process, please see the article link below. This is an awesome article about printing on dark garments by Tom Vann and Charlie Taublieb from impressionsmag.com. � 2009 Nielsen Business Media, Inc.