Flat Sheet Litho

While offset and flexographic printing are the two main ways envelopes are printed, there is a third way which is very commonly employed; lithographic printing on large, sheet fed and web presses.

These presses are typically employed by printing companies which provide high quality, full color printing on sheets up to 28 x 40 or larger. If a customer has an envelope that requires full ink coverage on all sides or even very heavy coverage on just one side, then it must be printed on a flat sheet which is then die-cut and converted into an envelope.

There are two main reasons why this approach must be taken. First, conventional envelope printing presses like the most commonly used Halm Jet presses are not able to print full coverage on all sides of a made envelope. As my previous post on flexographic printing explains, full coverage can be printed this way in-line but it’s only cost-effective at quantities of at least a few hundred thousand, usually more. The second reason is that when jet presses print heavy solids on a pre-converted envelope, there are problems that can ensue. Two of the main ones are seam marks and offsetting. When a heavy application of ink is applied in this way, the seams usually become visible due to the combination of dense ink and the pressure of the print rollers. Offsetting occurs when dense concentrations of dark ink are applied to an envelope. As the envelopes come off the press, they come in contact with one another before being scooped up in bundles and put back into a box. The rubbing or scuffing causes the heavy ink solid to come off onto the envelope that is next to it. What is left is ink residue that usually shows up on the back of the envelopes when the heavy coverage is printed on the front where it mostly is done.

Offsetting can be mitigated or eliminated by using a UV dryer which applies extra heat to the envelope as it comes off the press which can dry the ink sufficiently to prevent it rubbing off. This approach is workable but slows down the process and adds cost to the job.

Printing an envelope on a flat sheet and converting it after the fact eliminates any seam marks or offsetting. It is a more expensive way to go but yields excellent results and is very common in high-end direct mail pieces. One of the disadvantages of this approach from a customer’s standpoint is that it almost always requires dealing with two different companies for the same job. There are very few companies (none of which I am aware) that have both the printing and envelope equipment necessary to do both components.

At Kenmore Envelope, we have the expertise to handle the printing in conjunction with one of our many printer customers as well as the envelope equipment necessary to cut, glue and fold the paper into a high-quality envelope. We also have digital printing capability which works quite nicely for small quantity jobs (up to 2,500) at a very competitive price.