You may have heard this term before. But do you know what gum breakers are?
Gum breakers are small ridges that appear on rotary press printed stamps. Rotary press stamps had a tendency to curl because they were printed from large rolls of paper. Sheets of stamps would curl in postal workers drawers and cause many problems. Gum breakers are small ridges created during the perforating process. They were supposed to "break" the gum to prevent curling.
Gum breakers are a natural part of the stamp production process. Stamps will show small ridges on the gum side, almost like tiny speed bumps. Each ridge is about 1-2 mm. wide and runs the entire width of the stamp. Some collectors may mistake these ridges as a crease. They are not. Stamps may show one or more ridges depending on the spacing used.
Gum breakers were used on many stamps from about 1920 up to about 1970.
Martin Armstrong identifies three different configurations of gum breakers. All breakers are horizontal to the top and bottom of vertically oriented stamps and horizontal to the left and right sides of horizontally printed stamps.
Type I has four to five bars spaced about 5.5 mm apart. These were used on Scott #581-591 and on some early printings of Scott #632-642.
Type II has one bar per stamp. The bars are spaced about 22 mm apart. It is possible for a stamp to have two bars – one at the very top and one at the very bottom of the stamp. The Kansas-Nebraska stamps (Scott #658-679) only have Type II gum breakers.
Type III has two bars per stamp, about 12 mm apart. These are found on most of the Scott #632-642 issues and on all of the Scott #692-701.
Type IV was not identified by Armstrong. This type is similar to Type I. There are four or five bars, but they are at a slight angle to the stamp, approximately two degrees. These bars are not quite horizontal with the stamp.
Because the Kansas-Nebraska issues are so frequently faked, one quick way to check mint copies is to look at the gum breakers on the back of the stamp. If there is one bar (Type II), then there is a pretty good chance that it’s a genuine stamp. If there is more than one bar (other than one being at the very top edge and another being at the very bottom edge of the stamp), then it is a fake and it cannot be a genuine Kansas-Nebraska issue. Fakers sometimes forget to account for the gum breaker configuration and they will use another stamp to produce their fake.