Checking Watermarks On Covers

I have some old US covers that require checking watermarks to determine which stamps are represented on them.

How is this done?

And if it can't be, why does Scott list these varieties on cover?

Morley-Bright products are reputed to be able to check watermarks on cover. Never tried it but you can "google" for information.

how about a version of ground penetrating radar... watermark detecting radar?

;-)

It is always the best watermark on cover and the least watermark off cover.

Thanks for mentioning the Morley-Bright, scotzm, I will look into it. But I guess that apart from that, no one really knows.

Out of curiosity, with what the vast resources of the Internet might supply, I just did a search on 'checking watermarks on philatelic covers' and at the very top of of google was my own question, that's right, this post!

Proving google can be as dumb as a post!

I think Bobgggg just beamed this over to me...

Hold a lighter under it and as the paper chars, the watermark will appear.

I have been confronted by this question on quite a few occasions. If the stamp is on cover and the envelope happens to be made out of very thin paper, then you can usually see at least part of the watermark if you hold it directly up to the sun (in bright daylight). Unfortunately, sometimes you have to slit the envelope at that corner to be able to view the stamp from behind. However, this is obviously better than soaking the stamp/s off altogether. This has worked for me about 50% of the time. In the other cases, the problem was usually that the envelope paper itself carried a design, which made it impossible to distinguish the watermark on the stamp from the design on the envelope paper.

Thanks, jimjamtwo. It's supposed to be cloudy and rain hereabouts for the next few days, but I will see what can be seen in the sunshine, next week.

Somewhere on scf is a post where (I forget who) was explaining indepth scanning methods that with the right adjustments you could pretty well extract even on cover . I do believe the examples were strong obvious marks so depending on what stamp it is ther is hope. The principle was extracting postmarks but same method worked on some examples. You really have to know your software to do the right adjustments. I've played with saturation and contrast to see things better but your really asking to look through a brick wall.

Thanks, nitrolures, I actually remember something like that from when I was more active here. Will do some searching, though it seems like any keyword could bring up a gazillion posts.