How the Stamp Was Printed, and How to Tell

Three processes account for nearly all classic stamps, and they are distinguishable with a fingertip and a magnifier.

Engraved, or recess printing

Also called line engraving or intaglio. The design is cut into a plate, ink fills the recesses, and paper is pressed into them under great pressure.

The result is ink standing above the paper surface. Run a fingertip lightly across the design and you can feel it, particularly across dense areas.

Under a magnifier the lines are crisp, of varying width, and appear slightly raised with a faint ridge at their edges. Shading is achieved by line thickness and spacing rather than by dots.

This was the standard for high-quality stamps for a century and it remains the hardest to forge convincingly.

Lithography

A planographic process — the printing surface is flat. Ink transfers from a flat plate where the image area accepts it and the non-image area rejects it.

No relief at all. The surface feels completely smooth, and under magnification the lines are softer at their edges, sometimes slightly ragged, with no ridge.

Modern offset lithography uses a screen for tones, producing a regular dot pattern visible under magnification.

Typography, or letterpress

Relief printing, the reverse of engraving: the raised parts of the plate carry ink. Pressure squeezes ink slightly outward at line edges, and from the back of the stamp an impression of the design is often visible as a faint embossing.

Look at the reverse. A typographed stamp frequently shows the design pressed through.

Photogravure

A twentieth-century process, recess-printed but from a screened plate. Under a magnifier the whole design — including areas that should be solid — is broken into a fine regular grid of cells.

That all-over screen is diagnostic and separates it from engraving, which never screens.

Why forgers use lithography

Because engraving requires a skilled engraver and a press capable of great pressure, and lithography does not.

A large share of classic stamp forgeries are lithographed copies of engraved originals, and the fingertip test catches them. It will not catch a competent modern forgery, which is why anything valuable goes for certification as forgeries, fakes and why certificates exist sets out — but it catches a great many.

Fitting it into identification

Printing method belongs alongside watermark and perforation in the identification sequence in identifying an unknown stamp.

It is also the quickest of the three to check. Feel the stamp before reaching for the gauge or the fluid, because the answer sometimes narrows the catalogue search immediately.

Combination printings

Some stamps use more than one process, typically an engraved central design with a lithographed or typographed frame in a second colour. Feeling only the centre, or only the frame, gives half the answer.

Check several areas of the design. A stamp that feels raised in one place and flat in another is a combination printing, and catalogues describe those explicitly.

Colour changelings and re-entries

Two further things a magnifier reveals, both catalogued and both valuable.

A re-entry is a doubling in part of the design, caused when a plate was re-worked and the original impression was not fully removed. It appears as faint doubled lines in one area only, and is specific to particular plate positions.

Colour changelings are stamps whose ink has altered through exposure to light or chemicals. They are damage rather than varieties, and distinguishing a genuine colour variety from a changeling is one of the areas where certification matters most.