Scanning To Display Watermarks

I found a really good website for utilizing a scanner for philately. Really good read if your into combining technology with stamp collecting. Here's one topic that has been talk about before here.

www.pgacon.com


Scanning Watermarks

In some areas of philately, watermarks are very important and can make the difference between a $2 stamp and a $2000 stamp. The ability to create digital scans of stamps that show the watermark will be useful to many philatelists. I have devised a technique that can be used to create such scans. It can be used only with a flat-bed scanner, and may not work well with the less easily seen watermarks.

You will need a flat-bottomed container with a clear glass bottom, preferably with a lid. Do not use plastic as watermark fluid may dissolve some plastics. The size of the container does not matter, although a smaller one will be more convenient and will require the use of less watermark fluid. As long as you can lay the stamp flat on the bottom, that is all that is required. I use a Petri dish, a round flat container used in biological laboratories (see photo). You also need a small piece of black material - I cut one from the black backing on a stockcard. Finally you need some watermark fluid. I use SuperSafe Philatelic Watermark Fluid. The photo shows, from left to right, the lid and the base of the Petri dish, the piece of black material, and a 5-1/2 inch long pair of tongs to provide scale.



Here's how the technique works:

1. Place the stamp, face up, on the bottom of the container.
2. Add enough watermark fluid to cover the stamp.
3. Place the piece of black material over the stamp, pressing down to be sure that there is no air between the material and the stamp.
4. Put the lid on the container and place the container on the bed of your scanner.
5. Scan as usual.

Here's a scan of a Germany Scott #95 made using this technique. This is the raw image which was scanned at 200 dpi in 24 bit color.



After a bit of manipulation - converting the image to grayscale and increasing the contrast - the pattern of the watermark is clearly visible, as shown here.



If you cannot find a suitable container for scanning your watermarks, I have heard from some other collectors that you can do without one. Simply put the stamp directly on the glass of the scanner, put a drop or two of fluid on the stamp, and then press the black background over the stamp, using a small weight to hold it in place. Of course you would want to do this away from the edges of the scanner glass, to prevent the possibility of fluid dripping down into the scanner mechanism.

Another approach to scanning watermarks was told to me by Mr. Jim Sorenson of Madison, WI. His steps are:

1. Cover the scanner bed with a sheet of clear plastic to protect against possible dripping watermark fluid. You want a fairly stiff  plastic that will not wrinkle and degrade the image.

2. Dip the stamp in watermark fluid and remove any excess.

3. Put the stamp in a black plastic stock card with a clear plastic front flap. Use care to avoid air bubbles as much as possible. Try redipping the stamp if bubbles are present.

4. Place the stock card face-down on the scanner bed.

5. Place another sheet of black plastic over the entire assembly to suppress reflected and scattered light, then close the scanner lid.

6. Scan at 200 dpi using "color photo" mode. This resolution would not be adequate for examining most stamp details but is acceptable for identifying watermarks.

Now you have your image and can apply various image processing techniques to clarify the watermark. For example, edge sharpening and smoothing may help make the watermark stand out better. Some sofftware (e.g., HP Image Zone) allows color filtering, which may be helpful for suppressing the stamp design and permitting clearer presentation of the watermark. You can convert the image to black and white if desired. The figure shows a scan of watermarks made with this technique.