Defining the optimum ink deposit for UV starts before the ink is applied-Part II

When printing UV ink, two additional variables that are occasionally overlooked are the squeegee and ink viscosity.

Squeegee
Keep it sharp. The properly selected mesh, appropriate stencil build and superior ink cannot compensate for an improperly adjusted, worn out or poorly-maintained squeegee.
There are several squeegee considerations in applying a proper, uniform deposit of ink:
Determine that the blade you are using is resistant to UV formulations. If a blade is not universal it could work very well with solvent-based inks, but could swell or deteriorate very quickly when introduced to UV ink. This could drastically alter the uniformity of the ink deposit. Make sure that your squeegee is sharp and well-maintained. Ink cannot be transferred through mesh consistently with a dull or nicked blade. Slight imperfections in the blade can negatively affect the print quality when using UV ink.
Sharpen your blade only after it has been out of the ink a sufficient time for it to fully recover.
Do not use a solvent wipe to remove dust after sharpening, as it will swell the blade. Any solvent absorption could cause the blade to swell.
Develop a squeegee rotation program that designates three squeegees to each press. Use the first today, the second tomorrow, and the third the day after. This rotation will allow each squeegee two days between printings so it can fully "recover," and be properly sharpened before use. Adjust the squeegee angle and pressure to allow the blade to remain at the correct printing angle. Too much pressure or angle will allow the blade to bend severely and result in poor print quality.

Ink Viscosity
The viscosity of a UV ink can affect the amount of ink deposited and therefore, the cure energy required and color density may both vary. While the majority of Sericol's UV inks are formulated to be press ready, variations in screen mesh, substrate, climate, and individual variations in presses can lead to the need for slight modifications. For instance, UV inks may need to be thinned 2%-5% when printing with a cylinder press, as opposed to using without thinning on a clamshell or a four post semi-automatic press. Sericol's technical personnel are available for on-site assistance in recommending the proper print viscosity for each of our formulations based on your equipment, substrate, and other variables. Another consideration when talking about viscosity is temperature. Temperature can have a tremendous effect on the viscosity of the ink itself, which can lead to printing inconsistencies. As ink cools it becomes thicker. For instance, if a can of ink comes off a truck in Minnesota, during February, and sits on a dock all weekend, it will most likely need time to warm up to the normal printing temperature before using. Although it will probably print immediately, the ink deposit will change drastically due to the inconsistent viscosity. This same principle applies to warm climates as well. If the ink is warmer than usual, it will effect the viscosity, and therefore the ink deposit through the screen.
Remember, even though there are many variables in printing UV ink that need to be monitored and controlled, the benefits far outweigh the liabilities.