Paper and gum: reading the back of a stamp

Stamps · 8 September 2026

Two stamps can share a design, a colour and a perforation and still be different catalogue entries, because the paper or the gum changed between printings. Both live on the side collectors look at least. Reading them takes no equipment beyond a light source and a magnifier, and it settles questions that the front cannot answer.

Four readings on the paper

1. Thickness. Thin, ordinary or thick. Compare against another stamp of the same issue rather than judging alone – the difference is real but small, and comparison makes it obvious.
2. Surface. Wove paper looks even against the light; laid paper shows parallel lines; chalk-surfaced and coated papers have a distinct smoothness and matt sheen.
3. Colour and toning. White, cream, greyish or yellowed. Age-related toning is even and usually starts at the edges; a printing on genuinely tinted paper is uniform and intentional.
4. Fluorescence. Later papers often contain brighteners that respond to ultraviolet, and some issues carry printed phosphor bands for sorting machines. A UV lamp is optional but it separates modern printings quickly.

Hold the stamp against a light source for the first two readings – the same transmitted-light method used for watermarks in the guide to seeing a watermark, and often both can be read in one look.

Four states of gum

• Original and undisturbed. Even, unbroken, with the texture the printer applied. The top state for unused classic material.
• Disturbed. Hinge marks, patches where gum was pulled away, or areas smoothed by damp. The commonest condition on older stamps, for the reasons in the guide to hinges and mounts.
• Regummed. New gum applied later to imitate the top state. Signs: gum running over the perforation tips, a too-even sheen, and paper that feels stiffer than it should.
• No gum. Washed off, never applied, or removed deliberately. In humid climates collectors sometimes prefer it, because original gum can crack the paper as it ages.

What paper and gum decide

They separate printings. A design issued over several years frequently appears on more than one paper, sometimes with a different gum, and each combination is catalogued apart – which is exactly why long-running definitive series are harder than they look, as described in the guide to definitives and commemoratives. They also carry condition information that the front hides completely: thins, repairs and old hinge damage are all back-side findings.

How to check without causing damage

1. Use transmitted light and a magnifier. Never wet an unused stamp to test paper – water dissolves the gum you were assessing.
2. Compare with a second example of the same issue; absolute judgements about thickness or shade are unreliable.
3. Keep the check short. Repeated handling of a gummed stamp does more damage than any single reading is worth.
4. Record the result in your list beside the perforation and watermark, following the guide to cataloguing a collection.

Where to compare

Reference images show fronts, not backs, so the archive settles the design and the catalogue number while the paper and gum stay a matter for the stamp in your hand. The open archive holds 80,472 stamp images from 271 countries and territories and 6,382 Soviet issues of 1918–1991 with catalogue numbers – enough to identify the issue first, which is the step that tells you which papers to expect.

Open the catalogue: world stamps, Soviet stamps.