| An envelope is a packaging product, usually | | | | including a return envelope in the contents |
| made of flat, planar material such as paper | | | | of the original envelope. The direct mail |
| or cardboard, and designed to contain a flat | | | | industry makes extensive use of return |
| object, which in a postal-service context is | | | | envelopes as a response mechanism. |
| usually a letter or card. The traditional | | | | |
| type is made from a sheet of paper cut to one | | | | Up until 1840 all envelopes were handmade, |
| of three shapes: the rhombus (also referred | | | | each being individually cut to the |
| to as a lozenge or diamond), the short-arm | | | | appropriate shape out of an individual |
| cross, and the kite. These designs ensure | | | | rectangular sheet. In that year George Wilson |
| that when the sides of the sheet are folded | | | | in the U.K. patented the method of |
| about a delineated central rectangular area, | | | | tessellating (tiling) a number of envelope |
| a rectangular-faced, usually oblong, | | | | patterns across and down a large sheet, |
| enclosure is formed with an arrangement of | | | | thereby reducing the overall amount of waste |
| four flaps on the reverse side, which, by | | | | produced per envelope when they were cut out. |
| virtue of the shapes of sheet traditionally | | | | In 1845 Edwin Hill and Warren de la Rue |
| used, is inevitably symmetrical. | | | | obtained a patent for a steam-driven machine |
| | | | that not only cut out the envelope shapes but |
| When the folding sequence is such that the | | | | creased and folded them as well. (Mechanised |
| last flap to be closed is on a short side it | | | | gumming had yet to be devised.) The |
| is referred to in commercial envelope | | | | convenience of the sheets ready cut to shape |
| manufacture as a '"pocket"' - a format | | | | popularized the use of machine-made |
| frequently employed in the packaging of small | | | | envelopes, and the economic significance of |
| quantities of seeds. Although in principle | | | | the factories that had produced handmade |
| the flaps can be held in place by securing | | | | envelopes gradually diminished. |
| the topmost flap at a single point (for | | | | |
| example with a wax seal), generally they are | | | | As envelopes are made of paper, they are |
| pasted or gummed together at the overlaps. | | | | intrinsically amenable to embellishment with |
| They are most commonly used for enclosing and | | | | additional graphics and text over and above |
| sending mail (letters) through a | | | | the necessary postal markings. This is a |
| prepaid-postage postal system. Envelopes are | | | | feature that the direct mail industry has |
| useful. | | | | long taken advantage of -- and more recently |
| | | | the Mail Art movement. |
| Window envelopes have a hole cut in the front | | | | |
| side that allows the paper within to be seen. | | | | Most of the over 400 billion envelopes of all |
| They are generally arranged so that the | | | | sizes made worldwide are machine-made. The |
| sending address printed on the letter is | | | | envelope-machine making industry is dominated |
| visible, saving the sender from having to | | | | internationally by Winkler and Dunnebier. |
| duplicate the address on the envelope itself. | | | | |
| The window is normally covered with a | | | | Post office requirements |
| transparent or translucent film to protect | | | | |
| the letter inside. In some cases, shortages | | | | Post offices prefer envelopes to be |
| of materials or the need to economize | | | | rectangular rather than square, as this |
| resulted in envelopes that had no film | | | | reduces the amount of sorting that is needed |
| covering the window. One innovative process, | | | | to line up all the envelopes with the |
| invented in Europe about 1905, involved using | | | | addresses reading the same way. |
| hot oil to saturate the area of the envelope | | | | |
| where the address would appear. The treated | | | | Australia |
| area became sufficiently translucent for the | | | | |
| address to be readable. A typical use for | | | | In Australia, post office-preferred envelopes |
| window envelopes is courtesy reply mail. | | | | have four boxes printed in orange ink at the |
| | | | bottom right-hand corner where handwritten |
| An aerogram is related to a lettersheet, both | | | | postcodes are meant to be written. Character |
| being designed to have writing on the inside | | | | recognition software is used to read the |
| to minimize the weight. Any handmade envelope | | | | postcode number. |
| is effectively a lettersheet because prior to | | | | |
| the folding stage it offers the opportunity | | | | The Reply Paid is a system whereby a customer |
| for writing a message on that area of the | | | | may reply to a sender, with the sender |
| sheet that after folding becomes the inside | | | | bearing the cost. Specially printed envelopes |
| of the face of the envelope. | | | | are used, with the sender's address and the |
| | | | words "Reply Paid" with an authorization |
| The "envelope" used to launch the Penny Post | | | | number. The stamp is replaced by three black |
| component of the British postal reforms of | | | | stripes. The sender pays the postage plus a |
| 1840 was a lozenge-shaped lettersheet. But if | | | | fee to the postal authority. The customer may |
| desired, a separate letter could be enclosed | | | | write the Reply Paid envelope out by hand. |
| with postage remaining one penny, provided | | | | |
| the combined weight did not exceed half an | | | | Other countries use freepost as well, |
| ounce (about 13 grams). This was a legacy of | | | | although the envelope designs required by |
| the previous system of calculating postage, | | | | those countries' postal authorities differ |
| which partly depended on the number of sheets | | | | widely from that described above. For |
| of paper used. | | | | example, in the U.S., Reply Paid is called |
| | | | Business Reply Mail. |
| A "return envelope" is a preaddressed, | | | | |
| smaller envelope included as the contents of | | | | Envelopes in the Soviet Union were printed |
| a larger envelope and can be used for | | | | with something like the common 7 segment LCD |
| courtesy reply mail, metered reply mail, or | | | | display, to assist the user to write the |
| freepost (business reply mail). Some | | | | 6-character postcode directly in |
| envelopes are designed to be reused as the | | | | machine-readable format. |
| return envelope, saving the expense of | | | | |