Monday, September 14, 2009
The Oven Part 2: Web Growth
In the world of web printing, the web roll is pulled through an oven to dry the ink to the paper. This is done to take advantage of in-line finishing that a web press is capable of. As the form leaves the oven, it is completely dry and ready to be folded. While this creates efficiencies and cost savings, it can also result in an unattractive phenomenon called web growth.
Have you ever seen a catalog that looks like the cover was trimmed about 1/32 short of the text? This is a result of a sheetfed-printed cover binding with web-printed text. A few days after binding the two together, the text will physically expand. What has actually happened is that the text has swelled slightly after absorbing moisture from the air. The OVEN is the culprit. When the text is pulled through the oven to dry the ink, the moisture already in the paper is literally cooked or sucked out. For a consistent product and ease of handling, the folded text signatures are then baled together tightly. They remain air tight right up until the point that the bales are cut and the signatures are bound together and trimmed. After the product is completely bound, is the first time the text is exposed to moisture in the air. Over the course of a few days, the moisture creeps back into the paper and web growth begins.
What can you do to combat this? The best remedy is to print the cover and the text on the same press, however this often isn't the most economical solution. Another solution is to trim the books post web growth, but again this adds time and costs. Perhaps the only real remedy is to accept web growth is possible and thus design your piece to eliminate how much it stands out. Placing a coordinating color on the outside bleed edge of the first text page can eliminate how noticeable it is.