Overprinting refers to the process of printing one colour on top of another in reprographics

Reprography

Reprography is the reproduction of graphics through mechanical or electrical means, such as photography or xerography. Reprography is commonly used in catalogs and archives, as well as in the architectural, engineering, and construction industries....

. This is closely linked to the reprographic technique of 'trapping'

Spreading and choking

Trapping is a term most commonly used in the prepress industry to describe the compensation for misregistration between printing units on a multicolor press. This misregistration causes unsightly gaps or white-space on the final printed work...

. Another use of overprinting is to create a rich black

Rich black

Rich black, in printing, is an ink mixture of solid black over one or more of the other CMYK colors, resulting in a darker tone than black ink alone generates in a printing process....

 (often regarded as a color that is "blacker than black") by printing black over another dark colour.

It is also the term used in the production of envelopes customised to order by printing images (such as logos) and texts (such as slogans) on mass-produced machine-made envelopes; the alternative way of producing such envelopes is to print "on the flat" and then cut out the individual shapes and fold them to form the envelopes. However the latter method is generally only economically viable for large print runs offering returns to scale

Returns to scale

In economics, returns to scale and economies of scale are related terms that describe what happens as the scale of production increases in the long run, when all input levels including physical capital usage are variable...

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