The Anatomy of an Envelope
The anatomy of an envelope illustrates why heavy ink coverage in certain locations on the envelope may show a faint line. The drawing shows that envelopes have two areas ñ the seam overlap on the left and right ñ where there are two plies of paper. And since envelopes are printed with the flaps closed, that adds an additional ply where the flap covers the seam overlap.
Envelopes printed on an offset press contact a blanket a spongy material wrapped around the press cylinder. The sponginess of the blanket provides some give, allowing the inked blanket to adapt to a paper surface that might not be entirely even. But when the blanket encounters two or three plies of paper, it can’t adapt enough. The result is an uneven ink lay-down in those areas.
Normally this isn’t apparent. But if the art design of the envelope calls for a heavy solid in one of these multi-ply areas, the ink coverage may be compromised.
If you require an envelope with heavy ink coverage in an area, please call us to see if it would be best to have the envelopes printed prior to converting (the process of making an envelope from a flat sheet).