How to Watermark Stamps
by Kathleen Wunderly
Watermarks have been part of the process of making paper for hundreds of years. When paper was made by hand, wire would be twisted into a design, and the water in the paper pulp containing the wire would drain away, leaving a mark on the resulting sheet of paper.
Watermarks in paper made by machine are impressed directly into the paper when it is still damp. The design in watermarked paper - some currency, and fine quality writing or typing papers - can be seen by holding the paper up to a bright light. They were a form of security device, to make counterfeiting more difficult.
All British stamps beginning with the first one in 1840, the Penny Black, up to 1967 have watermarks, and some British Commonwealth countries still have watermarks. The United States printed stamps on watermarked paper from 1894 to 1915, in a design showing the letters "USPS," in two different typefaces (single-line or double-line). Other countries have used crowns, stars, even animal images, as watermarks.
Stamp catalogues illustrate the main designs of watermarks, and which stamps may be expected to have them. Don't expect to find a watermark on all stamps from all time periods! It is fun to find watermarks, but sometimes it also can be financially rewarding, if you are able to identify stamps that are rarities not because of the design on their face, but because of the watermarks in their paper.
If you can't see a watermark by holding a stamp up to a strong light, the next most common method for finding it is by using watermark fluid, a highly volatile chemical that will wet the stamp for a very short time, to allow a watermark to show, and then evaporate. Don't drown the stamp! A few well-placed drops of fluid are all that you need. Small black plastic watermark trays are available from stamp dealers, but any shallow black object will work for watermarking, such as an ashtray or a small plate or dish.
Some collectors will tell you that lighter fluid is a good watermark fluid. While lighter fluid will work for this purpose, it is not safe for you and possibly not safe for your stamps. Lighter fluid is highly toxic to breathe, and also is highly flammable. There also is reason to believe that lighter fluid (a petroleum-based product) may leave an oily residue on stamp paper, which would be damaging to it.
There are several watermark fluids available from stamp supply dealers. All of them should be used with care (use in a well-ventilated room, and do not breathe the fumes), but any of them are safer than lighter fluid. A company named Preservation Technologies has just developed a watermark fluid that contains no hazardous chemicals, and yet has the same evaporation rate as the other watermark fluids. It is called Clarity and should be available from the usual philatelic supply dealers.
There are several mechanical devices on the market for watermark detection, most of which use a concentrated light source to focus on the stamp, which may be pressed tightly against a viewing screen. Some of the mechanical watermark detectors are expensive; you may want to try one out on a few of your difficult stamps before buying it, to make sure it will meet your needs. Perhaps a friend will let you try his or her detector, or a dealer will allow you to experiment before buying.
Most philatelic experts rely on a combination of watermark fluid, mechanical equipment, good lighting, and knowledge to identify watermarks.