As you get into stamps, you are going to find that many issues of stamps exist printed on watermarked paper. Not only that, but often the same stamp will exist with 2 or 3 different watermarks, and the stamps will also exist with the watermarks inverted, sideways, reversed, sideways inverted and sideways reversed. In many cases, the differences between these varieties in terms of value can be significant.
So, it is important to acquire the equipment to be able to detect watermarks accurately if you are going to collect stamps from the British Commonwealth early United states before 1920 or most European stamps issued before the 1960's to name just a few. In fact, most countries' early stamps have watermarks. Canada is one of the few countries whose stamps are generally not watermarked.
So what are your choices? What means can you use to detect watermarks. Well, you have four options:
- Use a black watermark tray and watermark fluid to reveal the watermark.
- Use a black watermark tray with no fluid.
- Use a Morley-Bright ink satchet detector to reveal the watermark.
- Use a Signoscope unit to illuminate the watermark.
The cost and effectiveness of each of these methods depends on the type of stamps you are working with. There is no single method that works perfectly with every type of stamp unfortunately.
The classic, most common piece of equipment that most collectors use to detect watermarks consists of a small black tray about an inch deep, and hydrocarbon fluid that can soak the stamp to reveal the watermark, without affecting the ink, or the gum on the stamp, and which will evaporate off the stamp leaving it dry. Hydrocarbon is recommended because it is non-aqueous, and will not affect the gum of the stamp. In the past, many collectors have used lighter fluid or benzene. I do not recommend these for two reasons:
- Benzene is a known carcinogen that is very easily absorbed through the skin. Trichorotrifluoroethane is a much safer alternative and is what is sold today, like the bottle shown.
- Benzene and lighter fluid have been known to cause inks on stamps printed using modern photogravure to run, although they are generally safe for engraved stamps.
Generally, this method works very well for most stamps issued before the chalk surfaced papers became widespread in the 1970's. Here is what the tray looks like with a stamp and the fluid inside it:
As you can see, it shows the watermark up very nicely.
However watermark fluid is expensive now. The 4 ounce bottle that I show here cost me almost $20 with tax, and it doesn't last very long, especially if you do not close the cap tightly after use. Many a time I have failed to close the bottle tightly enough only to come back to an empty bottle a few months later. So, another option is to use the tray without the fluid, like so:
This isn't nearly as clear, but if your eyesight is good, it isn't bad. You can identify the watermark clearly and can see that it is upright. It probably won't be useful for very complex or symmetric watermarks where you need a perfectly clear view to ascertain that it is not reversed or inverted. But, this method will work well for most 19th century and early 20th century stamps.
It does not work so well on the chalk surfaced 20th century stamps, because the fluid will not generally saturate the chalk coating, but will highlight it, causing it to obscure the watermark.
Morley Bright Detector
This device unfortunately is no longer manufactured, due largely, I think to its lack of popularity among collectors. Like a lot of devices, one has to know how to use it properly for it to work, and my belief is that most collectors simply did not know how to use it properly. It functions on the principal that a watermark is a thinning of the paper that is extremely minute. The way it works, is that a sachet of ink is smoothed out so that the ink inside is evenly distributed. The stamp is placed on a flat surface, the ink sachet is placed on top of the stamp and gentle pressure is applied. The pressure will cause the ink to become attracted to the thinner areas where the watermark is, which will leave a visible pattern in the ink. The secret to using it successfully of course is to ensure that the ink in the sachet is evenly distributed through the sachet before you start. If you do not do this, then it won't work very well. Also, if you crease the sachet through mishandling, that won't work either.
It is the only method that you can use for stamps on cover, and when used properly, with experience, it works quite well for stamps issued before the 1970's. The main drawback with it is the ink sachets have a limited shelf life and have to be replaced eventually, and they are no longer manufactured. However, it is possible to find used ones on the market, and replacement sachets if you look patiently enough. It will last you a long time if you use it sparingly for checking stamps on cover only and use a tray for your other stamps.
The last option and most expensive is also the only one that will really work for modern post 1970 stamps printed on chalk surfaced paper. The signoscope is essentally a unit about a foot long and 8 inches high. It contains a battery powered light in the body of the unit on the left, a light well on the right, and a glass block on a hinge and aluminum tray that slides out, like this:
The glass block lifts up. The stamp is placed underneath it, and then this entire unit slides back into the main unit. The light is switched on, the large white handle, which is normally pointing out when the unit is open, is pulled closed toward the unit as shown above. This places pressure on the glass, which causes the light shining up through the stamp to reveal the watermark, like this:
A dimmer switch on the left side of the unit allows you to adjust the brightness of the light until the watermark shows up the most clearly that it can. As you can see, this isn't really any better on this stamp. However, it is the only way you will be able to see most watermarks on post 1970 stamps. The problem is the chalk coating: it generally obscures the watermark. This unit generally allows you to shine just enough light through the back, that you can see the watermark.
However, it is very expensive, at around $250 for a unit. It is also not quick to use because of the setup involved. Even though it is a 2-3 minute set up, it means that checking 100 stamps would be quite time consuming. So, it is not recommended, or really necessary of you are only collecting stamps issued before 1970.