Watermarks - again...

A device like this is on my shopping list. I just would like to see some real world examples (pics) of various types of watermark detection method (various fluids, machines) in use and what types of watermarks they work best. I have heard these type do not work well for US stamps.

Before you go high tech to discover watermarks, make sure you try the low tech version - just put the stamp against black paper and use a strong light for viewing. Many watermarks can be seen this way and you don't risk hurting yourself (with fluids like benzene) or the stamp. I use twin spotlamps that are mounted to my desk. This allows me to see almost every watermark. The ones I can't see don't seem to be visible with watermark fluid either. I have tried the pressure detectors like the one shown above and they seem better, but they are kind of expensive.

I do have a Signoscope, and love it. As KGVI, I detect most Wmks simply on my black deskcover, if no good I proceed with liquid. The last resort is the Signoscope, model T1. Typically the modern GB Commonwealth stuff ends up being studied in the Signoscope to make any sense of it. I can confirm it works better for most of the difficult watermarks out there, like any yellow colored stamps, or early GB on colored paper which is often awkward, as well as the hard to detect Wmks on US Washington/Lincoln's. I have also experienced that liquid sometimes work better than the Signoscope, without me being able to see a pattern of that, however in most of the difficult cases the Signoscope comes to the rescue. It's a bit expensive, but I've already made some good discoveries I wouldn't have been able to without, so for me the investment is worth every penny.

The thing to be aware, is that it takes a little more time than the other methods, even with the full-scale model that applies pressure with a handle, like T1. I also tried the smaller version, T2, but that model applies pressure with 4 different screws, which I really did not like because it simply took too much time, hence if you like to invest, do not go for the semi-version, you would want the 'Mercedes'.

Another thing to be aware is that the Signoscope works best when the back of the stamp is clean, any hinges or paper remnants make it less efficient, however still useable in most cases.

Conclusion - personally it's something I could not manage without!
Jon

AFAIK, pressure is the key for the method of using light source coming in from the side to reveal the Wmk (like the Signoscope). This method needs the paper to sit hard against the flat surface (the glass). This will create 'shadow' areas where the paper is thinner, which is what the Wmks actually are, patterns of slightly thinner paper. The more pressure, the more the paper will sit perfectly flat, and the shadow areas get more prominent. I believe this is the explanation, anyway, someone can probably explain it better.

Some of reading watermarks come from experience. I often see something (like all those crown CA) but not enough to be sure. This comes from doing it often enough. This is especially true for US USPS single line watermark when you only have a small part on the stamp.

I read two specific points - sandwiched in glass and side illumination. I am guessing the more oblique the angle the better.

Just sharing some bits and pieces.

I have been exploring a DIY "Roll-a-tector" approach, using plastic bags containing a dab of viscous goop. Results have been fair. See thread "Dangerous DIY watermark detector." I haven't worked on it for a while, though (too many other projects), but expect to be getting back to it soon.

I have only done some beginning explorations of a DIY Signoscope approach, using glass, with unsatisfactory results. I need to develop a mechanical system to apply the pressure, and that may require buying some plexiglass/lexan. The light coming from the side should be a point-source, and I think I have solved that by using the flashlight on my smartphone, which is very small and remarkably bright.

I use a Signoscope T1. I don't know what I would do without it. It makes even us with less than perfect vision able to see any watermark. I got mine on Ebay a few years back for dirt cheap, because no one else bid on it.

Oh no, seigaku! I tried this, now all my mint stamps are missing the gum!

D'oh! Did you take the opportunity to write down the watermark types and catalog numbers on the backs of those stamps?
(just kidding too--it scares me that somebody out there might take me seriously)