Trapping generally refers to overlapping colors that are adjacent to one another and occurs with all designs. Even with the best presses, there tends to be some movement from color to color when trying to register them without leaving a white gap between them. While newer presses may claim to be able to register color to color with very little trap being applied, it is just good sense to make some allowance to help make the printers job easier and the customers' satisfaction greater. Having said this, if you apply too much trap between medium hue colors they can create a darker line where they meet. The trick to what works best for you and your equipment is to carry out regular finger printing to help determine the sort of registration that can be held and is particularly important on older equipment as bearings and gears begin to wear.

     Having an experienced prepress operator that has plenty of separation experience can make the art of trapping look easy, but even with newer software that can be used to apply trapping between colors automatically there is a great skill to being able to help make any job either easy to print, or a nightmare if care is not taken when applying trapping. Always try to explain to your prepress house/customer what you need to produce a good print for them and do not be afraid to adjust your files to what you need and not what someone else thinks you need. This can be particularly difficult when a customer is more accustomed to offset printing where little or no trapping is often the norm.  

     It should first be understood that all VDP (Variable Data Printers) are not all capable of producing the same images at the same speed. That said, most systems are capable of producing sequential numbering, 1 and 2 D bar codes, random numbering, harvest marks and graphics. Speed and resolution of print can and does vary a lot from machine to machine. Again, although most substrates can be printed on including absorbent and non-absorbent materials, not all VDP systems offer the variety of inks to be able to do this. Most systems only print in one color — that being black — but more advanced systems can print in other colors and other specialty inks.