Working With Heavyweight Cover Stocks

Heavy cover weights have been a significant trend in the print and design community for the past few years. Where 100#C was once considered standard, it pales in comparison to the 120#C and 130#C that have become today’s norm. In the past, printers have cringed when these basis weights were specified on a job, especially if you were going to flood the sheet with ink. With a little planning, the end result can be well worth the minimal effort and expense to upgrade to a heavier cover stock for next print project. Here are some tips to help you successfully execute your next project on a heavy weight cover paper.

Separations – these are pretty important, especially if you’re printing on an uncoated stock. To compensate for dot gain, you’ll want to open the separation allowing the pressman to print to normal ink densities. This will yield more accurate print fidelity, brightness and crispness of the image. This also allows a finer line screen to be utilized (175 and up). A traditional uncoated paper may allow you to open the midtones from anywhere from 9-15%.

Cutting – it’s important to remember that when working with a heavyweight cover, you’ll need to adjust the lift size, clamp pressure, and angle of the blade.

Folding and Scoring – when you’re working with a heavy cover weight, you definitely need to score the sheet first before folding. This may seem like a no brainer, but it this should be done with the grain of the paper. (Tip - grain direction is always the second number in the sheet size dimension, ex. On a 23” x 35”sheet, the grain direction would be on the 35.”) You’ll want to use a rounded rule or channel matrix for best results. For a clean fold, the ratio of the paper’s caliper (thickness) and width of the creasing channel (matrix). Testing is always a good idea. In general, you can find the right proportion by multiplying the caliper by 2 and then adding the width of the creasing rule. It’s recommended that scoring and die-cutting be done on a flatbed die-cutter to minimize risk of cracking. Cylinder letterpress scoring can be difficult with heavyweight covers. If possible, run the score to the end of the press sheet, ensuring that the piece has a complete score. Also, be sure to decrease pressure points that are caused by folding. If the paper breaks near a folded corner, try sanding or shaving down the ends of the creasing matrix where the miter joint occurs and leave a little space between the ends by slightly backing off the miters.

Also worth mentioning are considerations for perforations and climate control. Keep in mind a perf that runs with the grain will tear more easily than one that’s against it. When it comes to temperature, you really want to keep it to 70-75 degrees with humidity around 40-50%.

Due to the heft of the paper, offsetting can become an issue when working with heavyweight covers. It’s recommended to use spray powders with large particle size, running at a minimum of 45 microns – this allows for greater air circulation and better ink drying.

Remember, it’s always a good idea to test the sheet first, to request samples of a heavyweight cover stock for your next project, click here.