Wednesday, February 3, 2010

Putting a glow in your presswork - OBAs and black light posters

Most printers who are faced with a printing job that's intended to glow under black light tend to think only about the issues of printing with fluorescent inks (see the post HERE). However, there is another important item that needs to be considered and that is the effect that the amount of, or lack, of OBAs (Optical Brightening Agents) in the paper will have on the final result.

For example, viewed under a black light this poster "glows" in an expected way:And it will look similar, except for the glow effect, under normal room and black light conditions.

However this poster which has large areas of white, i.e. unprinted paper, looks very different under normal house light:compared with being viewed under black light:
The difference in appearance is caused by the amount of OBAs in the paper. In this example, the paper contains low/no OBAs. Under normal home lighting the paper looks white and the fluorescent inks fairly bright. However, under black light the inks glow brightly but the paper which contains low/no levels of fluorescing agents goes dark - there is effectively no light for the paper to reflect.

This difference in color response can be used creatively or it could destroy the intended look of the poster as envisioned by the artist.
If a paper with high levels of OBAs is used instead, then the appearance of the image would be preserved under black light:
So, when quoting a "black light" job consider the amount of OBAs that the paper contains because it can have a profound effect on the final result. If the paper will have 100% ink coverage then choose a paper with high OBA content to assist in the final glow effect. If the design includes areas of white, then discuss the issue with the original designer and choose a paper that has high, or no OBA, content according to the final result the designer is trying to achieve.

To determine the relative amount of OBAs in the paper, view a sample using an inexpensive fluorescent type black light:

No comments:

Post a Comment