a watermark in stamp paper can be seen just by looking at the unprinted back side of a stamp. More often, the collector must use a few basic items to get a good look at the watermark. For example, watermark fluid may be applied to the back of a stamp to temporarily reveal the watermark. Even using the simple watermarking method described, it can be difficult to distinguish some watermarks. Watermarks on stamps printed in yellow and orange can be particularly difficult to see. A few mechanical devices are also used by collectors to detect watermarks on stamps such as the Morley-Bright watermark detector and the more expensive Safe Signoscope. Such devices can be very useful for they can be used without the application of watermark fluid and also allow the collector to look at the watermark for a longer period of time to more easily detect the watermark. See also Digital watermarking Thomas Harry Saunders Allan H. Stevenson Overprinting Overprint References Further reading Buxton, B.H. The Buxton Encyclopedia of Watermarks. Tappan, N.Y.: Buxton Stamp Co., 1977 114p. Felix, Ervin J. The Stamp Collector's Guidebook of Worldwide Watermarks and Perforations, from 1840 to date. Racine, WI.: Whitman Publishing Co., 1966 256p. Repeta, Louis E. Watermarks In Postage Stamp Paper: a comprehensive look at a key stamp element. Reprinted in 1999 from The American Philatelist (February 1987). 27p. External links WZMA - Watermarks of the Middle Ages Briquet online (in French) Piccard online (English) Watermark Database of the Dutch University Institute for Art History Bernstein - The Memory of Paper, Portal to 50 Watermark Databases Watermarks 1850-date Finding Watermarks on Stamps: Hobbizine article Thomas L. Gravell Watermark Archive Thomas Gravell watermark collection, Special Collections, University of Delaware Library, Newark, Delaware. Archive of Papers and Watermarks in Greek Manuscripts The History of Watermarks on U.S. Stamps 1895-1916 Watermark discussion list Philatelic terminology Money forgery Papermaking Stationery Banknotes Italian inventions io:Filigrano