Just Say "No" to Cracks

Smooth, straight, crackless scores. Whether you are running saddle stitched books, perfect bound books, pocket folders or tent cards, you need scores that fold where they should, look neat, and don't crack.

Cracking scores can ruin a nice looking job as fast as a horde of "hickies" in a halftone, and it sure is discouraging to work through a great printing job and then have the spine crack during the last operation. Scoring may be a simple part of the job, but if it doesn't get the attention it deserves, you may end up with the lithographic phenomenon known as "the dreaded reprint."

When to score?

There's really no need to get into detailed specifics about which basis weights in what stocks require scores for a clean fold. Obviously cover, index, bristol, tag, and heavy text would normally be scored, but the bottom line is that if the job cracks, or the folds aren't locating accurately without being scored, you need to score regardless of the stock type or weight.

Also, jobs that will be folded later (a tent card for example) need a score as a folding aid and location guide.

There are three general ways to score a sheet of paper.

First, the litho score.

The simplest way to score a sheet of paper is to use a litho-score on an otherwise unused cylinder on your offset printing press. The advantages are great if you have an unused cylinder (i. e., a one-color job on a 2-color press) and there isn't any ink coverage along the score line. In this case, it doesn't take a separate press run, the set-up is simple, and the cost is low. You ruin a blanket, but you often can save the blanket and use it for several scoring (or perforating) jobs. Of course, you wouldn't even think of charging each scoring customer for a new blanket, now would you.

Here's a tip from Richard Booth of H. S. Boyd Company, manufacturer of litho score material. Richard suggests that his product will work on stocks up to approximately .012" thick. He cautions that litho score material is best used to locate a fold and to make folding easier. Its primary function is not to prevent cracking.

Next, the folding machine.

A folding machine score, much like the litho score, is used primarily to locate a fold and to make folding easier. The quality is comparable to a litho score, and like the litho score, it isn't used when the highest quality is required or when cracking is a significant problem. Positioning is less accurate than litho score on long narrow sheets.

If you're scoring and folding an uncoated stock on a folding machine, and you're having trouble with cracking, try running a bead of 50% alcohol and 50% water along the score line before folding. This softens the fibers and allows a smooth fold.

Third, the channel score.

Our final type of score is generically referred to as a channel score. The common element of all types of channel scores is that they form a bead on the stock by use of a male/female die set. The old letterpress crowd will remember wire and string scores, which formed the fold bead by forcing paper over a wire with two blunt rules. The channel score commonly used today involves a scoring rule to drive the paper stock into a "channel" created on the bed of a platen press or on the cylinder of a cylinder press. When the fibers of the paper stock are pushed into the channel, they are elongated adequately to allow them to wrap around a 180° bend.

This is the most accurate score, and it gives the best crack prevention of the three basic types of scores. Ninety percent of the time, a standard channel score on either a flatbed (platen) press or cylinder press will do a great job. However, there are two types of jobs that are real bears to score: jobs with dark coverage on coated stocks and jobs with a UV coating.

For the tough jobs.

First, plan to make your score across the grain of the stock. This somewhat unconventional attack to the problem allows the paper fibers to wrap around the fold and helps hold the sheet together.

If you're using a cylinder press for one of these challenging situations, plan your layout so that the critical scores are parallel to the cylinder for a better result. Cylinder presses always give a better score parallel to the cylinder rather than perpendicular to the cylinder. If you're still having problems, try a platen press. The platen press will usually provide a significantly better score than a cylinder press.

UV coated sheets are probably the toughest challenge of all. The heavy deposits used on silk screened spot UV sheets give the greatest challenge. Without a platen score you're dead, and even with a platen score you may not always be able to eliminate cracking. The best solution is to use spot UV, keeping the coating away from the area to be scored.

The last resort.

One final thought if you've tried everything and your scores still crack. You can use a heated score on a press with a heated bed (i.e., an embossing/stamping press). The heat will soften the paper and allow a rupture-free score. This is expensive, and is definitely a last resort, but we guarantee it will be cheaper than a reprint!

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