December 08, 2005
Dissecting a CD for Design Sake
In this article we dissect a compact disc and analyze how the individual parts provide unique challenges for design and printing on a CD. Knowing the medium you're designing for helps prevent unwelcome surprises in the final product.
Main printable area: The main section of the disc. This is where the audio or data is encoded. Colors printed on this surface will tend to appear darker than they would on white paper. Depending on the ink coverage, differing amounts of the silver surface will show through. Higher ink coverage (darker colors, in general) means you'll see less of the reflective surface showing through. Less ink coverage, with print dots more spaced apart (lighter colors, in general), will reveal more of the underlying disc surface. The only way to have something appear white anywhere on the disc surface is to print with white ink (see "white base coat" below).
Mirror band: This is the ring area just inside of the main print area. The mirror band is not encoded with data so it has a different reflective quality, appearing darker than any other part of the disc. Generally the mirror band is etched with the name of the manufacturer, as well as a number or barcode identification associated with the client master. The effect of printing on the mirror band is a darkening of the text or images as compared to that of the main print area. Just inside of the mirror band is the stacking ring.
Stacking ring: On the underside of each disc, this thin ring of raised plastic is used to keep a small amount of space between each disc when stacked up for boxing and/or shipping. It prevents the flat surfaces from scraping against each other, which could scratch either the printed tops or the readable bottoms of the discs. Even though it is on the underside, some manufacturers are unable to print over the stacking ring area due to a small "trough" created on the top surface when they mold their discs. Other manufacturers mold discs that are smooth on the top and can print over the area.
Hub: This is the innermost portion of the disc, made of clear plastic, which includes the stacking ring. Printing over the hub area is similar to the effect of printing on transparency media. The lighter the color - the more the transparency effect is present, due to the small, widely spaced print dots that are used to produce light colors. With heavy ink coverage over the hub, the transparency is far less noticeable. However, all colors will appear different when printed over the clear plastic hub as compared to the other opaque surfaces of the disc.
White base coat: Applying a white base coat over the disc's entire print area before printing the design lessens the darkening effect of the mirror band, and also lessens the transparency effect of the plastic hub. The white base (sometimes termed "white flood") acts like a primer coat, so the final design more closely resembles printing on the white paper of standard jewel case inserts, wallets or Digipacks. If your disc design includes photos, particularly faces, a white flood will make them look more natural. Most manufacturers will NOT automatically suggest a white flood, and they may charge for it as they would any other ink.
True design encompasses much more than manipulating images, text and colors with computer programs. Even the most carefully chosen typeface won't communicate effectively if it is hard to read over the different areas of the disc surface. Clouds or snow on a cd design will only be white if you use white as one of your printed colors. The characteristics of the tangible item you are designing for play a critical role in the overall design process.
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