ENLARGED OFF-CENTER PORTRAIT
The portraits of historical figures featured on bills will be moved off-center and will include more detail. ``Humans recognize other human faces most readily.... [The greater detail] will enable regular people to better detect counterfeits,'' an official at the US Treasury says. Bills will retain their ``American'' appearance -
an important consideration since US currency is used as a medium of exchange in many countries.
These inks change color when viewed from different angles. For instance, an ink that appears to be gold when viewed directly may appear green when viewed obliquely. The ink will be used on a specific feature, such as on the seal or numbers.
DISTINCTIVE AND MACHINE-DETECTABLE FIBERS
These authenticity of these special fibers, which will be added to the paper, can be identified by machines. Modern security fibers are designed to incorporate many types of machine-detectable characteristics. ``We think that the [quality of the] paper is a very important counterfeit deterrence, because it's very hard for anyone to duplicate the feel and the look of US currency paper,'' the Treasury official says.
Traditional planchettes are colored pieces of tissue paper a few millimeters in diameter. They are incorporated into the paper, either in rows or randomly distributed. In newer planchettes, features such as microprinting and iridescence enhance the bills' security.
A watermark is an image formed by creating localized variations in paper density during the papermaking process. The image is visible as a lighter area when held against a light source. Similar to the embedded thread, it does not copy on color copiers. The watermark will be a smaller image of the portrait.
A security thread is a thin thread or ribbon running through a banknote. It can be microprinted, metallic, magnetic, windowed, and/or embedded. The thread used in US currency is an embedded/microprinted thread that is visible when held to a light. This makes it impossible to copy on a color copier, which uses reflected light to generate an image. Clear polyester security threads were added to the 1990-series $100, $20, and $10 bills; they will be added to $5 bills this fall. In the new design, each denomination will carry a thread in a different location.
MOIRE-GENERATING LINE STRUCTURES
These types of line structures appear normal to the human eye but cannot be properly resolved by scanning equipment such as a photocopier. Copying results in moire patterns that are noticeably distinguishable from the original. Think of it this way: ``If someone wears a striped shirt on TV, it sort of blurs for [the viewer] because the equipment doesn't have good enough resolution,'' the Treasury official says.
Microprinting is tiny type, which was also used in the 1990 series. Check the outermost border around the portrait on $100, $50, and $20 bills: ``THE UNITED STATES OF AMERICA'' is printed 12 times. Barely detectable to the eye, it also is difficult to reproduce. The new bills will include more microprinting than those already in circulation.