Sometimes It's Really Much Setoff On The Back Of A Rotary Stamp...

Hello,

as the topic of setoff on rotary stamps just was mentioned in the other recent thread below, I just wanted to show two stamps from my album. Actually since I found them I don't sort the setoff stamp out as flat so quickly anymore...

as explained here, setoff at rotary stamps is also possible:
http://www.stampsmarter.com/learnin...methods.html

but as written there, is seems to be possible only on top of the gum. But still impressive sometimes. Actually I don't have a real question about those stamps, only perhaps why mostly we don't see any setoff at all and then there it is, so what went different on those cases in the printing process?

Not sure how to tell when the ink transferred to the gum of the stamp; during the production process or years later due to improper storage?
Don

The setoff on flat plate wet printed stamps occurred under the gum because after printing sheets were stacked on each other to dry before they were gummed. Since most sheets were stacked squarely on top of each other, the setoff tends to be on the back positioned just as if it was under the front matching design of the stamp.

The setoff on rotary press wet printed stamps could occur on the gum after the drying and rolling up of the printed paper roll for seasoning after gumming or anytime after the printed paper rolls were cut into sheets and were stacked to be cut into panes or the panes were stacked and/or stored on top of each other. The setoff on top of the gum appears more random in relation to the front stamp design.

We have all seen 'setoff' from completely different stamps...stack some mint stamps, place in a stock book, lay stock book flat for a while.

It is also not uncommon to find 'setoff' from images on printed albums pages. A gummed stamp can pick up almost anything if not handled/stored correctly.
Don

Looking at how complete the designs as setoff are, how they are positioned, and how detailed the fine lines of colors are reproduced, I think this happened during the printing process on my stamps. Interesting is, what parameters were different when there was setoff on the gum vs. no setoff.

jogil: thank you. do both parts of your explanation about rotary stamps talk about setoff on top of the gum? So is there probably no scenario in the rotary printing when such a complete setoff is applied under the gum?

In the Stickney rotary press between the stamp paper printing plate section and the stamp paper gumming section, the rolled out paper web moves in a continuous whole stream straight through a drying area so that there is no chance of it folding over onto itself to somehow come into contact with itself unless some break can occur in the paper web severing it and making it roll over itself.

thank you again, now I understood. I didn't ask this because of my stamps above, as they have the setoff on top of the gum without any doubt. Just wanted to know if there were other cases perhaps as well. By the way my stamps are both used, but seem to have maintained some gum.

IIRC, the unique Scott #613 strip of three was originally failed by expertizers because it did have setoff on the back, among other reasons. The owner was able to demonstrate by plating that the stamp was in fact from a rotary plate that printed #613.

sinclair2010: Some sheet and coil waste stamps can be exceptions because at some point in their production they were cut off the web and made into sheets earlier than normal due to some production problems.

sinclair, was this on or below the gum? and has there been an article about this maybe with scans of the setoff?

You can also observe ink offset in mounts when a stamp has been in them for some time. I see this at times when I take a stamp out of a collection or when it is in a mylar type 3x5 stock card.

This just demonstrates the fact that the ink, even though a hundred years old, can still migrate.

This is what Don was talking about when you see gum with offset on things like commemorative plate blocks which have been stored in glassines or in stock books on top of one another and would be another reason for the apparent offset. This one being a type which had nothing to do with the printing process, of course.

Provided that I am remembering things correctly, the offset was definitely on the stamp - it is a used strip. Ken Lawrence was one of the expertizers of the strip and he wrote an article, kind of a postmortem on the expertization of the strip that yielded results that were in error. The article was in Linn's or perhaps the journal of the USSS. I used to have an electronic copy that was provided by Ken on the old VSC but I can't seem to find it on my computer. Will look some more... Surely somebody other than me can provide it, the Scott #613 isn't even issued in the correct century

A pet peeve of mine when I buy multiple stamps and the seller throws them all in the same glassine and from the pressure/vibration of the mail they arrive with such a "setoff" - totally annoying to have a red stamp with green ink on the gum. Problem seems to be worse with modern US stamps that are intaglio printed that have dry (dull) gum.

It is possible that some waste sheets were cut off from the damaged paper web roll before they were gummed. They were stacked and gummed like flat plates and perforated like flat plates. The more copies found, the greater the possibility of this occurrence being found.

To address eyeonwall's point, most modern (1980-2018) water-activated stamps have PVA gum. This gum is very strong and can become activated with humidity. So, I wonder about all of those coil rolls that are lefty in boxes for years. Also, if you soak used stamps, you need to make absolutely sure that you remove ALL of the gum, or you will be in for a nasty surprise. This is especially the case if you store lots of them in tight glassines. When soaking, it is best to lightly rub the back of the soaked stamp and dip it again into the water. If you see any milkiness coming from the stamp, you know it needs more work.