Stamp information
What is used and unused?
When a stamp is as bought over a post office counter, and has never been on a letter, it is known as unused (if it has all its gum, it is called mint).
Once a stamp has been on an envelope, and a postmark applied, then the stamp is said to be used.
What are perforations?
The tiny holes around the edge of a stamp, intended to help tear stamps apart, are called the perforations. You may be surprised to learn that different sized holes are used, and stamp collectors measure the size by counting the number of holes in a length of 2cm.
There are gauges available which help you to measure the size of the perforations. Often two stamps can look identical, but can differ in the size of their perforations.
What is a watermark?
Very often in the past stamps were printed on paper which contained a design which could only be seen when the paper was held up to the light. If you take a banknote, and hold it up, you will see a watermark. Today far fewer stamps have watermarks.
How are stamps printed?
Many different processes are used, but most stamps these days are printed by a process called lithography.
However, many stamps from the British Post Office are printed in photogravure.
The stamp on the left is printed lithographically, the one on the right by photogravure – notice how much crisper lithography which is why old stamps look so good, despite being printed perhaps 150 years ago.