- August 07, 2003, Gerry D. Rector, Senior Product Development Manager, Neenah Paper
Sturdier and tougher, heavyweights have the advantage of being stronger—whether in a boxing ring or a box plant. While heavyweight papers aren’t as tough to work with as their boxing counterparts, they can present a unique set of challenges—and advantages—when using them to make packaging. So the critical question for converters is, "Just how do you work with heavyweights?"
Heavyweight papers—also called "covers"—are defined as 120lb. and heavier on a 20 x 26–500 basis. Always consider the caliper, or thickness, in addition to weight, when choosing a paper. Those with the lowest weight and the highest caliper are always more economical, since paper is priced based on weight.
For example, a 165lb. cover with a 21pt. caliper is seven percent thicker and has an eight percent lower billing weight than a 180lb. cover with a 19.5pt. caliper. This makes the 165lb. cover a thicker and more economical option. Not only does caliper help determine cost, it also plays a key role in heavyweight paper’s foremost feature: strength.
Remember that the corrugating medium enhances strength and can allow you to use a surprising variety of papers, including 120lb. papers (or "light heavyweights"). Today’s packaging is increasingly designed for point-of-purchase consumer use and high graphics applications. Premium heavyweight papers are the clear choice for these uses because they offer an unparalleled range of aesthetic and tactile qualities.
If it’s important that customers notice the packaging or, perhaps, if you want their fingers to linger on the box, consider premium papers. They are especially good for embossing, spot coloring, and a host of printing processes and finishes. Let’s say you’d like to match a box or carton to its contents—a cobalt and gold perfume bottle. You can easily coordinate the packaging color to the product. Using premium covers, you can achieve a color brightness and clarity that other heavyweight papers just can’t touch.
An excellent alternative to single-ply or solid covers are laminated covers, which are typically stiffer and more substantial. In addition, they have a better printing surface, since the papers being laminated are from lower weight sheets, offering better, more consistent printing surfaces.
There are two types of laminated covers. One, known as Double Thick Covers, are two sheets of the same color and weight paper laminated together. Laminated covers also are available as Duplex Covers, with different colors and/or textures on each side.
Premium covers, whether laminated or single-ply, are ideal for small-volume jobs that go to a limited number of end users such as fine jewelry or high-end cosmetics. For example, a major cosmetics company uses a 165-lb. Double Thick Cover for its upscale line of hair care products. Only sold in salons, the products convey a tacit message of quality through their packaging. The company selected a velvety, 99+ brightness blue-white paper, using this clean, pure color to highlight its commitment to nature and the environment. Packaging that’s constructed of premium heavyweight papers says: "This product is special. It’s a keeper."
While heavyweight and laminated covers offer numerous benefits, they must be handled correctly to avoid fiber cracking or lifting at the folds. To use heavyweight and laminated covers to their full beauty and advantage, consider the following tips:
- Basis Weight Conversion
Knowing the equivalent conversion from typical box basis weights to that of premium heavyweight packaging allows for an easier transition. Box basis weights are usually expressed in pounds per msf or mf (1,000 sq ft). Therefore, 1,000 sq ft of 90lb. box stock weighs 90 pounds. However, premium heavyweight covers are weighed in pounds of material per 1,800 sq ft. To determine the heavyweight equivalent of 90lb. box stock, multiply the box stock weight (90lbs.) by 1.8. The premium heavyweight paper equivalent in this example is 162lb.
Overall Converting Guidelines When Using Heavyweight Papers
- Prior to folding, wide-score the paper using a flat-bed press for best results. This will provide an even score on the whole sheet at one time, as opposed to a cylinder press, which scores only a small area at a time.
- Always fold toward the ridge or bulge in the paper. This will prevent cracking of the paper and will help to achieve a clean, smooth score line.
- Normally, score and fold with the grain of the paper. Scoring with the grain prevents cracking of the paper.
- If a cover needs to be folded both ways, make the primary fold with the grain.
- Consider using lighter screen tints or eliminating ink coverage over areas scored for folding to minimize highlighting paper fibers along the fold. This is particularly important when scoring against the grain or when using Cover, Duplex Cover and Double Thick Cover papers. You may avoid this and maintain the impact color provides by using colored paper instead of printing colored inks.
- When possible, score the paper while it is still moist from the litho press fountain solution to prevent cracking on the score due to dry-out.
- Always hand-fold complex folders and covers. Most folding machines can not handle the extremely complex folding jobs.
- Experiment to determine the best process for scoring your particular paper.
Scoring Heavy-Weight Papers
Heavyweight papers must be properly scored to fold easily. Follow these tips to help ensure proper scoring:
- Use a creasing rule/channel score for best results on cover-weight papers. This system includes a creasing rule or male die (preferably steel), combined with a channel or female die. The paper is sandwiched between the creasing rule and channel to make the score. The score appears as a ridge or bulge in the paper. Try these generally recommended combinations of creasing rules and channels:
1 & 2 point rule for a #40 channel
2 point rule for a #50 channel
2&3 point rule for a #60 channel
2 point rule for #75, #83, #90 and #105 channels (165lb.)
- On heavyweight stock, try a 2 point rule with a #60 channel as a more effective alternative to the recommended combinations.
- Consider using a lighter score over a heavy score to resist cracking when folding.
- When scores run down the cylinder on cylinder presses, try dulling the edges of the channel by filing down its surface to help reduce cracking on the fold, especially where two or more scores meet.
Scoring Against the Grain
While it is typically recommended to score with the grain, it is possible to score against the grain as well. Results will be enhanced by following these tips:
- A cut-score (or kiss-cut score) can be utilized when scoring and folding against the grain, or when fiber lift is a problem. A cut-score is a method of scoring wherein only a cutting rule (without the channel) is used to slightly cut through part of the surface of the paper, thereby creating a sharp and smooth break or fold in the paper at the point of the cut. This method is an excellent solution for cracking.
- Some duplex papers may score and fold better against the grain.
- Again, experimentation with various creasing rule/channel system combinations is recommended.
Die-cutting can be an excellent way to add texture and visual impact to a printed piece. Try the following tips when die-cutting on heavyweight covers.
- Die-cutting should be performed on a platen or flatbed press to minimize the possibility of cracking. Use a very sharp knife with the proper angle (60°) when cutting heavyweight covers.
- When scoring and die-cutting simultaneously, pay close attention to rule height. The cutting rule must be higher than the score to cut properly. For example, if your scoring rule is 0.900, your cutting rule should be 0.918.
Determining the right method for scoring covers and folders is still an individual process. These guidelines should be used as a starting point for experimentation. If you believe packaging sells, premium heavyweights are the ones to use. By handling them properly, you’ll be sure to create your next packaging knockout. For more information on scoring and folding, visit neenahpaper.com
© 2003 Neenah Paper
Gerry Rector is senior product development manager for Neenah Paper, the leading manufacturer of premium writing, text, and cover papers marketed under the CLASSIC ENVIRONMENT and other fine brand names. For more information about scoring and folding heavyweight covers, visit neenahpaper.com. Contact the author at email@example.com