The Watermark Detector

Primarily as a protection against counterfeiting, many stamps are printed on paper watermarked with some sort of device. All adhesive stamps of the United States were printed on watermarked paper from 1895 to 1916, and all United States embossed envelopes are on watermarked paper up to the present day. A watermark is merely a thinner area in the paper, which can be ssen by holding the paper before the light. A common example is an ordinary piece of "bond" paper on which may be seen, if held before a light, the manufacturer's name or trade-mark. How it gets there is explained in the chapter dealing with paper making. Before the stamps are printed thereon, the watermark can be easily seen by simply holding the paper in front of a light. But after the stamp has been printed it is no longer so easy to see the watermark. In fact it is often impossible to see it. Hence the watermark detector.

This is a simple device usually consisting of a glass tray with a jet black bottom. To use it, place the stamp face down in the tray and pour a little carbon tetrachloride over the stamp. (Ordinary "Carbona" will do very well.) The liquid makes the paper of the stamp translucent and the black bottom of the tray will be seen through the thinner parts, i.e. the watermark, which is thus revealed. Carbon tetrachloride is recommended as it is noninflammable. Many collectors use ordinary benzine which serves the same purpose.

Neither of these liquids will have any damaging effect upon the stamp or the gum of most stamps. Once the stamp has been subjected to either liquid, it should be placed on a clean piece of paper and in a few moments it will dry out completely. The liquid can be returned to the bottle for future use. Since watermarks greatly affect the value of a given stamp, they are of the greatest importance. However, not all stamps are watermarked so it will be necessary to use the detector only on such stamps as your album or catalogue indicates may occur in the same design but with a different watermark or, perhaps, without any watermark at all.

Watermark tray
Watermark shows against black background of a watermark tray.