Sealing Methods

A Blake Premium Peel and Seal Envelope

There are different envelope sealing types for different applications. Below are the most common sealing methods.

Gummed Envelopes

A water soluble gum – the most common sealing method and always used for 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 it is biodegradable. Only gummed envelopes are suitable for automatic machine inserting and the sealing is performed automatically by the mailing machine.

Self Seal Envelopes

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 twelve months from date of manufacture. However, in the correct conditions this may extend. An 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, self seal is derived from rubber and ammonium substrate, therefore the latex 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 Envelopes (or Powerseal)

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 and seal adhesive;

  • Cold melt which is like self seal latex, it has one band of adhesive which is covered by a large silicone paper strip. Envelopes with cold melt peel and seal normally have a shelf life of 2 years and;
     
  • Hot melt - the most common option of peel and seal envelopes we stock - has a narrow band of adhesive, this is of a heavier gram weight than normal peel and seal, and looks similar to double sided tape.

With this we can guarantee up to 5 years shelf life. Due to its sealing properties, hot melt peel and seal acts as a tamper proof security seal as it is impossible to open the envelope without tearing the flap. This type of sealing is also known as; Super Seal, Strip Seal and Peel and Stick.

 

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