During the 1970's-80's 3M Scotch used a foam inner backing beneath the top reel flange on the 400, 420, 479, and 8250 videotape products to reduce edge damage.
At some point, a different type of glue was used that would not set-up and dry, and leaked onto the tape surface creating a tremendous sticky mess.
3M made a valiant effort back in the day to replace all the affected flanges with the defective glue, but it was a very popular product and was distributed worldwide before the glue problem was fully realized.
There are a few reels out in the world yet with the defective foam glue, sitting on library shelves. How many, nobody knows.
Foam flange reels arrive here at the shop for transfer on a regular basis and most are generally in very good condition.
Occasionally a single reel or a collection of reels will arrive with the Flange Glue Syndrome. I have worked with it for years and have recovered quite a number of reels. Maybe 100 to 200 reels is my best guess. It does take a lot more time to clean glue off of video tape. For that reason, I charge $45 per reel extra for the glue removal work. There's no big secret to it, it just takes a lot more time, and a few extra things to work with such as Eucalyptus Oil. Cleaning is much more intensive of course.
The video and photo gallery below shows a few images of tapes with various glue and foam problems that I have worked with over the years.
It may help someone to better understand and identify tapes with these problems.
The long and laborious process of removing blobs of glue from the oxide layer by hand by soaking the glue with eucalyptus oil and gently scrubbing and wiping until all traces are gone.