all about envelope printing

Envelope Printing Glossary of Terms

Helpful information on envelopes and printed envelopes

Like many industries, the envelope printing industry has developed a language of its own.  To those familiar with the industry, the terms below will be part of their daily language, but if you are an occasional visitor to the world of envelope printing, many of these terms may be completely new or mean something entirely different to you!


Also known as ‘Invitation Envelopes’, these ones have a V-shaped or Diamond flap on the longer edge.


This refers to an envelope with a perforated tear-off removable section. The tear-off section is usually attached to the top of the back of the envelope, just below the flap.  Commonly used for both charity gift aid donation envelopes (so that you can put card details and other confirmation on the tear-off section and place securely inside the envelope), and for bank paying in envelopes.


Similar to Bangtail envelopes, the term bangflap is used to distinguish envelopes where the tear-off section is attached to the end of the flap, rather than the main body of the envelope.


Manilla Paper with a woven finish, often used for thicker manilla envelopes, most commonly of 115gsm weight.


Within the envelope printing industry, this term is usually used to refer to an envelope that is printed as a flat sheet and then made up into a bespoke envelope later.

Biodegradable / Recyclable

Whilst virtually all paper envelopes are 100% recyclable and biodegradable, envelope windows usually aren’t, however, there are ranges of envelopes with biodegradable windows.

Board Back

These envelopes have a paper front, usually around 120gsm, and a rigid card back, usually ‘greyboard’ or ‘chipboard’ of around 1000 micron.


This stands for Business Reply Envelope – these are non-window envelopes with the company name and address printed on the front, and usually a Royal Mail PPI or freepost account ref.  Designed to make it easy for the recipient to return documents to the sender via the post.

Colour Wash Envelopes

A printing technique that involves applying a solid single colour to the paper.  For a consistent even colour, Envoprint often pass envelopes through the litho printing machines several times.  Envelopes are notoriously difficult to colourwash as the underlying seams tend to lead to a non-solid colour if not done correctly, but over the years Envoprint has developed colour-washing to a fine art.

Corn Starch Window Film

A version of biodegradable envelope windows, making the entire envelope biodegradable within 30 days, instead of just the paper part of the envelope.

Card Envelope

Either an envelope constructed of thick paper or card, generally 200gsm or thicker, or else an envelope designed for greeting cards (diamond flap/banker envelopes).

Drilled Holes

Some envelopes, particularly those used for internal mail and within hospitals, have drilled holes so that you can instantly check whether they contain anything without opening it.

Flexo printing

A cheap printing technique normally carried out at the point of manufacturing the envelopes, suitable for large quantities and also where the high quality and detail of litho print is not required.

Flat sheet conversion

The make-up of envelopes from flat sheet sheets, normally pre-printed, allowing full bleed print and internally printed envelopes, and also special effects such as foiling, spot UV, lamination, embossing, debossing, are all suited to this method of envelope manufacturer.


Stands for Forestry Stewardship Council, possibly the most widely respected brand mark in the envelope industry for those who want traceability and to know the paper has been responsibly produced in an environmentally friendly manner.

Gift Aid Envelopes

Simply a donation envelope displaying the correct HMRC approved gift aid declaration, so that gift aid can be claimed on the contents.  For details on the latest government gift aid wording suggestions, please see the HMRC website.


A semi-transparent paper material similar to grease-proof paper or tracing paper, often used for seed packet envelopes.

GSM / Grammage

A measurement of grams per metre squared, the most common measurement of paper weights in the envelope printing industry.  Not a measure of thickness, see entry for ‘micron’ in relation to envelope thickness.


A gummed envelope needs moisture applying to the sealing strip to activate the gum adhesive.  These envelopes are often cheaper than other varieties, and are also the most commonly used by automatic mailing machines.

Printed Gusset envelopes

These envelope have expandable ‘capacity’ gusset folds at the sides.  Block-bottom gussets have a box-like base, and are quite difficult to overprint, V-bottom gussets have a v-shaped base and therefore slightly lower capacity, but are much easier to overprint and are also cheaper and much more commonly used.  V-bottom gusset envelopes tend to expand only as much as necessary, and are therefore useful when a varying amount of inserts may be enclosed, whereas block-bottom gussets work best when they are filled to capacity every time.  Envoprint have developed some unique methods of printing onto gusset envelopes, and are widely known within the envelope industry as the experts in this field.

Hot Melt

This is a high-quality seal sometimes used for peel & seal envelopes, and extends the traditional shelf-life of peel & seal envelopes from 2 years to 5 years.

Invitation Envelopes

Diamond flap envelopes, see ‘Banker Envelopes’ above.

Laser Window Film

Double normal window film thickness, so it can go through laser and digital printers without melting inside. It is usually 40-50 microns instead of the standard 22 microns.


Envelopes designed to run well through a mailing machine, usually they have ‘trap flaps’ or ‘trapezium flaps’, and they are usually gummed and usually have the flap on the long edge.  They are often slightly oversized to make it easier to set up on the mailing machine.

Mailing Wallet

See ‘Machineable’ above.

Matt Coated

Refers to a non-glossy lamination giving a subtle satin sheen and also waterproof qualities and tear-resistance.  Often used on some of the most luxury envelope options!


A measurement of thickness commonly used for paper and card.  Does not refer to weight, e.g. 100gsm is not the same as 100micron, although the gsm weight and micron thickness are often quite similar, just to confuse things!  Thickness above 300micron is generally referred to as card, below 300micron, paper, but there is no clear dividing line between ‘thick paper’ and ‘thin card’, in fact the 2 terms in reality overlap a little!


An opaque envelope inner is a printed design or wash inside the envelope to ensure the contents are not readable when the envelope is sealed.  Opaque inks are used to print onto dark coloured envelopes.  Normally only silver and gold opaque inks are available for litho printing, but with digital printing opaque white is also often used.  Or silver can be mixed with other colours to give a degree of opacity as well as a special sheen to the print.


A worldwide recognised colour reference system, very common within the litho printing industry, as pantone inks can be bought, ensuring consistent colour matching from one batch of printed envelopes to the next, and also allowing the printing of consistent brand colours by several different printers. Also referred to as PMS colours (Pantone Machine Service) and spot colours.


Stands for Portable Document Format, and is the most common form of file used for electronic artwork proofs.  Part of the Adobe range of software.


Programme for the endorsement of Forest Certification Schemes, allows you to trace where the paper for your envelopes originated.


Litho printing both sides of the envelope at the same time, ensuring the print is lined up on both sides.


Means ‘Pricing in Proportion’ is the main method Royal Mail now use to charge for mail based on size and weight, small letter, large letter, parcel, etc.

Pocket envelope

These have the flap on the short edge.


Stands for Postage Paid Impression e.g. 1st Class, Mailsort, and is often pre-printed onto envelopes in advance for clients who have a Royal Mail account set up.  It ideally needs to be situated 5mm from the top right corner and have a white area around it, but if the print design is sent to your Royal Mail account manager, they should be able to approve variations on this, e.g. on a gusset envelope you may need to position it 13mm in from the edge to avoid the seam, and Royal Mail are usually very understanding in such instances.

Reel Fed Manufacture

The cheapest way to make large volumes of envelopes, and print can be done in-line as part of the manufacturing process, however there are a number of limitations to this production method that limit it to simpler more basic items and high volume production.

Close Register / Loose Register

Close register is where the different ink colours used to print the envelope are very close or touching, meaning great precision is needed to ensure the inks don’t run into each other.  Loose register is where the individual colours are printed spaced widely apart, and is easier to print.

Self Seal

Refers to sealing method where the two flaps are pressed together to form an instant bond.

Security Slits

Some self-seal envelopes have small slits in their flaps, designed to tear when opened, giving a tamper-evident seal.

Shelf Life

The recommended usable life of an envelope.  Self-seal envelopes have the shortest shelf life, self-seal envelopes have the best sealing properties in the first 6 months, but will retain some adhesive properties much longer than that.  Peel & seal envelopes have great sealing properties for 2-5 years depending on the seal used (see ‘hot melt’ above).  Gummed envelopes have an indefinite shelf life, but must be kept completely dry or else their adhesive properties will deteriorate rapidly.  We would advise that gummed envelopes should last at least 5 years in a dry heated office environment.


The top of the side flaps of a wallet envelope. Mailing machines require that these be designed specially to allow trouble-free insertion.


This is where the print on one envelope transfers to another envelope during printing.  Unless great care is taken, set-off is likely to occur where the ink coverage is heavy and/or strong colours are used.  There are a number of methods we can use to eliminate or minimise this effect including running the print slowly or using an anti set-off spray.

Side Seams

The seams at the sides of a mailing wallet. Some mailing machines require these to be inside, and other mailing machines require them to be outside, so take great care to select the correct ‘inside seams’ or ‘outside seams’ option if you know the job is going to go through a mailing machine.

Tear Resistant

Constructed of a special tear-resistant paper such as Tyvek.  There are also envelopes made of special laminated paper that looks identical to normal paper both inside and outside the paper, but within the paper structure is a concealed layer of tear-resistant water-impenetrable material.  See our printed Tyvek envelopes page for further information on tear-resistant envelopes.

Thumb Cut

A shape cut at the opening of an envelope, usually a flap-less wallet, to allow easy opening or easy removal of documents, usually a semi-circle.

Tyvek envelopes

These envelopes have many unique properties associated with Tyvek material.  They are extreemly lightweight, have a special swirling layered texture, and are virtually impossible to tear (although they can be torn with difficulty along the folded edges and also at the seams).  They are also water-resistant.  There are many sizes available including gusset options, and bespoke sizes and styles can be manufactured to order if large quantities are required.  They are NOT made of paper. Printed Tyvek envelopes suppliers are hard to find, but Envoprint have this off to a fine art.

UV Dryer or UV Cured

A special fast-drying addition on some of our print machines, allowing print onto otherwise unprintable surfaces such as glossy coated envelopes and printed metallic envelopes, even glossy or metallic printed jiffy bags (also known as printed bubble bags or printed padded bags).


An envelope with the flap opening on the long edge.  Square envelopes are normally referred to as wallets too, but we’ll leave you to work out whether the flap on these is on the short edge or the long edge!

Undersize envelopes

These are designed to fit inside standard sized envelopes without needing to be folded, so are most commonly used as BRE Business Reply Envelopes.  The most common sizes are DL- (105x216mm or 102x216mm) and C5- (155x220mm).

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