Modern Stamps Issued With Dull Gum

Other than a Scott Catalog, is there is a online quick reference guide on which modern stamps were issued with dull gum? Is there a reason why such stamps were issued with dull gum? Seemed like an inconvenience for the average consumer back in the day.

It's all part of experimentation with an eye to transition to the newer dull gum. The different types of gum breakers used beginning in the 1920s show the progress in trying to keep panes from curling up in storage. All those different perfs for the Washington-Franklins were a long-running experiment to keep panes from falling apart in storage yet still remain easily separable by users.


How so? The average consumer wouldn't be concerned about the gum other than if it would stick the stamp to a letter.

hy-brasil: Stamps with dull gum in my opinion have difficulty sticking to envelopes when licked via tongue.

When compared to shiny gum, dull gum looks almost invisible as if there was no gum. The dull gum seems to be indicative of U.S. issues that were web-fed rotary press dry-printed on pre-gummed paper which started in 1971 with some booklet stamps. Further information is found in the following USPS Philatelic Release # 10: