Stamp Collecting with GS

Soaking and Collecting Self-Adhesive Stamps

Self-adhesive stamps are here to stay, and sometimes it seems as if they are truly stuck there forever. Self-adhesives are also known as pressure-sensitive stamps or peel-and-stick and were first issued by Sierra Leone in 1964, followed by Tonga and Bhutan in 1969.

They were something of a novelty item, an interesting philatelic marketing angle, like banana-shaped stamps or circular-hologram issues.

The USPS got into the act with the 1974 10¢ Christmas issue (Scott #1550), but the public and collectors were confused by the stamp and the issue was considered a failed experiment. People were leaving the stamp on the protective backing and taping and gluing them to their Christmas mail.

Today the used '74 Christmas stamps cannot be soaked from paper and the adhesive has disclored nearly all of the stamps, turning the white background an uneven blotchy brown. Mint copies can be saved by removing the sticky adhesive with an organic solvent such as naphtha as found in lighter fluid.

But that was then and this is now. The 29¢ Eagle and Shield stamp (Scott #2431) was the start of normal self-adhesive production in the US, and the public loves them. SA's represented just eight percent of the USPS's stamps in 1994, but a full 85% by 1998. Self-adhesives are now the norm over the time-honored lick-'n'-stick stamps.

Four Layers

A typical mint self-adhesive stamp has four layers.

Protective Backing; the slick, shiny, non-stick packaging; not really part of the stamp but essential in manufacture and storage.

Self-Adhesive Layer; the sticky side of the stamp; two types of adhesive have been used in self-adhesive stamps.

Binder; a thin chemical layer that stops the adhesive from "bleeding" into the stamp design and discoloring it; it's soluable in water so that when the stamp is soaked, the binder layer releases the stamp paper from the adhesive that still adheres to the envelope.

Stamp Paper; the printed paper top of the stamp bearing the design and other postal indicia.

Adhesives

There are two basic classifications of self-adhesive glues.

Rubber based: old technology; like the glues used in old cellophane tape; not archivally safe; penetrates paper; darkens in color; and loses adhesion (stickiness); used on the '74 US Christmas stamp; recommended that the gum be dissolved in organic solvents.

Synthetic polymer based: used on US self-adhesives since '89; not archivally safe; won't yellow, dry out or become brittle; subject to "cold flow," adhesive can ooze out around the edges of the stamp and possibly stick to a mount or album page; adhesive quality improves with age; softened by organic solvents and leaves a residue behind that can be rubbed off.

Soaking Self-Adhesives

Soaking water-activated gummed stamps means diluting the glue that hold the stamp to the envelope paper. Soaking a self-adhesive stamp means dissolving the binder later, which then releases the stamp paper from the adhesive still stuck on the envelope.

Soak water-activated stamps and self-adhesive stamps separately. Traditional gummed stamps use lukewarm water and will float free long before the SA's.

Soak SA's 30 to 45 minutes in warm to hot water, but we wary of colored envelope paper bleeding their inks into the bath. SA's float off coarse enveloped more quickly than other covers.

The longer an SA stamp has been on the envelope, the longer it will take to soak off because its adhesive quality improves with age, so soak those new SA stamps today.

The stamp inks on SA stamps are stable when soaked for prolonged periods.

After soaking, the stamp may remain in place on the paper, but if you gently slide it between your thumb and forefinger it may come off. Avoid tongs after a long soak as the paper is very fragile.

SA stamps curl when drying. Place another layer of blotters on top of them and weigh them down.

Stubborn Stamps

If an SA stamp won't come free after a good soaking, the binder layer may have failed and the adhesive may be bonded directly to the stamp's top paper layer. Naphtha or turpentine can loosen the adhesive, afterwhich you must gently rub off the adhesive residue

"Un-du" is a heptane-based, adhesive remover sold in craft and variety stores. It can loosen stubborn SA stamps, but it can also affect some cancellation inks.

1989-90 Autopost and Postage Validation Imprinter metered strips do not have a binder layer. Soaking does not release the stamp from the envelope: the adhesive holds the stamp paper to the envelope.

The 1999 Sonoran Desert stamps may need to soak over night in hot water.

See other material on soaking stamps.

Mints, Covers and "Cold Flow"

Some stamp collectors favor the removal of the self-adhesive layer on mint stamps because of the cold flow or edge ooze problem, though removal of gum from a mint lowers its acceptability in the eyes of some collectors.

Do not peel the stamp from it's original protective backing. Use adjacent stamps for postage and trim a 1/8" border around the stamp. Mount it, but periodically inspect it for cold flow.

Cold flow can cause trouble for cover collectors. Not only can the adhesive seep out around the stamp and into the envelope paper, but it can react with the inks in the envelope itself. discoloring the envelope or turning it translucent.

Ink, binder and adhesive chemical formulations continue to change so be alert for news of particularly stubborn stamps, and if you have an SA tip please post it for others to read.