There are two basic styles of envelope – Wallet or Pocket.
- Wallet: If the flap is on the long edge of the envelope then this defines the envelope as a wallet or a banker. A banker envelope has a diamond shape flap and is traditionally for use in the greeting card industry. We refer to these as Greeting Card or Invitation Envelopes. A wallet envelope normally has a trapezium shape to suit automatic mailing machines (but can be straight or slightly curved).
- Pocket: If the flap is on the short edge of the envelope then it's called a pocket. The most common pocket envelopes are C5 and C4.
- Gusset: Usually a pocket envelope with expandable sides to increase the capacity of the envelope, they can have either a block bottom or V bottom. These are typically quite high grammage envelopes designed to handle brochures or multiple leaflets.
- To measure the size of an envelope, the side where the flap is on is always given as the last dimension, e.g.
- 110 x 220mm indicates a wallet or a banker
- 220 x 110mm indicates a pocket.
- A combination of the traditional Imperial and the European metric sizes has resulted in a wide range of envelope sizes. In addition to the stock sizes available, there are almost an infinite range of envelope sizes that can be custom made. In reality though, the high demand is for a basic range of sizes, which are:
- DL 110x220mm Takes A4 folded in three, width ways
- C6 114x162mm Takes A4 folded in half & half again
- C5 162x229mm Takes A4 folded in half
- C4 324x229mm Takes A4 unfolded
- C5+ 162x235 or 162x238
- DL+ 114x229 or 114x235
- Gummed Envelopes: A water soluble gum – the most common sealing method and always used for machinable mailing envelopes. Moisten the layer of adhesive along the envelope flap and close. Providing these envelopes are stored in the correct conditions they should last for a number of years. The gum is water soluble and usually made from a blend of synthetic resin and dextrin, therefore is biodegradable. Only gummed envelopes are suitable for automatic machine inserting and the sealing is performed automatically by the mailing machine.
- Self Seal: This method of sealing has a strip of latex on each flap and is pressed together to form an instant bond. The latex on self-seal envelopes normally only has a guaranteed shelf life of six months from date of manufacture. However, in the correct conditions this may be extended. Equilibrium of temperature is essential, not too hot and not too cold, hence the reason we have controlled heating in the warehouse in the winter and cooling in the summer. Also known as Dri-seal, Press-seal & Fast-seal, it’s derived from rubber and ammonium substrate and the latex therefore can be classed as a natural product. On the flap of Self Seal envelopes you will sometimes find Security Slits. These slits will cause the flap to rip if the seal has been tampered with.
- Peel and Seal: One of the most secure ways to seal an envelope, peel away the release tape from the flap to reveal a strip of latex and press down to form an instant bond. There are two types of Peel & Seal adhesive: cold melt which is in effect like Self-Seal latex – one band of adhesive covered by a large silicone paper strip; these normally have a shelf life of 2 years. The other type which covers most of the Peel and Seal range we stock is made with the hot melt process which is a narrow band of adhesive with a heavier gram weight than normal Peel and Seal looking similar to double sided tape. This offers up to a 5 year shelf life and due to its sealing properties, acts as a tamper proof security seal as it is impossible to open the envelope without tearing the flap. Also known as Super seal, Strip seal & Peel and Stick.