Sub Navigation
Additional Content
Quality standards
Notes for envelope manufacturers and importers and printers, advertising agencies and lettershops.
The paper used to make envelopes should meet the following minimum quality standards:
Density
DIN standard 680, ISO standard 536
The actual paper density should not differ from the nominal density by more than 8%.
Paper thickness
DIN standard EN 20534
The actual paper thickness should not differ from the nominal paper thickness by more than 8%.
Specific strength
DIN standard 53112 ISO standard 1924/2
Minimum specific strengths dependent on density:
| Density | Longitudinal fibre direction | Diagonal fibre direction |
|---|---|---|
| 80 g/m2 | 4,700 m | 2,900 m |
| 100 g/m2 | 4,500 m | 2,900 m |
| 120g/m2 | 4,100 m | 2,500 m |
Permeability to air/porosity
ISO standard 5636-3 ISO standard 8791-2
To allow vacuum technology to be used as well, porosity should not exceed 650 ml/min. (Bendtsen method).
Smoothness/roughness
DIN standard 53107 + DIN standard 53108 ISO standard 5627 + ISO standard 8791-2 and 4
Mechanical separation of letters is usually readily possible provided they have a smoothness (Bekk) of around 18 to 30s.
Transparency/opacity/transparent papers
ISO standard 1831
For the address to be machine-readable there must be no interference from characters showing through when the address area is illuminated. This means that the address needs to be printed on a material with a minimum 85% opacity. In the case of window envelopes, there is a danger of characters on the paper which lies beneath the address impairing the legibility of the characters which form the address.
Tip: use paper with a density of 80 g/m2 or higher. The opacity of such paper is normally not critical.
Transparent paper envelopes are often unsuitable for machine processing. Firstly, characters below the address section show through and impair readability. Secondly, barcode adhesion is poor and smearing occurs during subsequent processing. Transparent envelopes are therefore classed as special items subject to a surcharge.
Tip: if you pre-sort such items, you will save yourself the surcharge for manual sorting or will at least benefit from a reduced surcharge.
