We all carry around plastic ID cards of one type or another but most people don't know a lot about them. If you like to find out how stuff works you may wonder what ID cards are made of and how the pictures are printed on them so they don't rub off. Also, how does that black stripe on the back work? Here are some basic answers.

Card Materials

The majority of plastic cards in circulation today are made of poly vinyl chloride. PVC is the second most commonly manufactured plastic worldwide and is very cost effective to produce. The substance is made by exposing vinyl chloride to a polymerization process that allows the molecules to create long networks or chains that are very strong. The resulting powdered PVC resin is heated and rolled into sheets which are then die punched into individual cards. Pigments can be added to the mix during the heating process to create different colored cards.

Card Varieties

Layers of Mylar, paper, or adhesive may be added as a final step for use in different applications. Cards can also feature either a matte or slick finish to suit different printing styles. Composite cards have a polyester core layered between PVC sheets to give them added strength. These are more expensive than regular cards but can withstand more abuse. Earth friendly cards made of recycled PVC are now available from environmentally conscious distributors. In addition to choosing this option you can also increase sustainability by collecting your company's obsolete cards and turning them in for recycling. Just don't mix them with other types of plastic since PVC needs to undergo a different reclamation process.

Thermal Printing

The most common type of ID card printing is simple thermal transfer using some type of resin based ink. The ink coated ribbons run through a card printer and are pressed against the surface of each card or transfer sheet. The print head is heated to release the ink from the ribbon onto the printable area where it bonds tightly with the surface creating a smudge proof result. Ribbons are typically formatted in a reel to reel design and the ink is laid out in repeating segments of yellow, magenta, cyan, and black. These colors are applied in layers one after the other to create a high quality replica of a photograph or other complex image. Plain black ribbons are available for simple jobs that don't require color.

Magnetic Stripe Encoding

The black or "HiCo" magnetic stripe on the back of many cards is made of plastic with an admixture of powdered iron oxide. A powerful electromagnet locks the particles of metal in opposing orientations and varying sequences within the plastic stripe. This creates a binary code - the same type that computers use to function. When the card is swiped through a reader these particles are briefly reactivated so that the encoded information can be retrieved. "LoCo" magnet stripes that don't require a very strong magnetic field to program are also available, but this variety is more susceptible to being accidentally erased.