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Pros and Cons of Pre-, Post- and No-bake Plates

October 2000
BY MOLLY W. JOSS


Here's a riddle for you: It's not cake batter, it's not cookie dough, but you still have to bake it to get the most enjoyment out of it. What is it? To some the answer will be obvious: it's a printing plate.

Even if you didn't guess the answer to the riddle, you may still find yourself deriving enjoyment—or at least increased print runs and other benefits—from baking digital plates. Depending upon the plate and the print job it's intended for, you stand to gain significant production advantages by using a plate that requires baking either before or after imaging. You can also derive benefits from plates that require baking for longer print runs. If you'd rather leave the baking to bakers, you can find some plates on the market today that do not require baking at all.

But choosing to use baking in your plate production process is not without its downsides. The upside of cake and cookies is the enjoyment of eating them—the downside is the calorie intake. The upside of baking is composed of the production benefits—the downside can be additional costs and time. The overall benefit you derive overall lies in how you put the "recipe" together.

When you heat a plate before you expose it, you open up avenues to several benefits, including the use of inexpensive radiant heat, not expensive laser light, to prepare the plate for imaging. You still have to image the plate, but pre-heating means the plate is warmer that it would ordinarily be when it enters the imaging stage. Thus, less laser energy is required during the imaging process.

With thermal plates, pre-heating creates a negative-working plate, which can then be used with either other thermal plates or conventional, negative film.

Jeffrey Zaloom, director of R&D for PDI, says that pre-baking is required when using some thermal plates. "Pre-baking thermal CTP surface plates is necessary to fully expose the image. Portions of the plate exposed to the platesetter form a strong acid in the coating matrix. Heating catalyzes the reaction between the acid and polymer to either cause crosslinking or de-protection of the polymer system to create an image."

Likewise, post-baking (heating the plate after it has been imaged, but before it goes on-press) offers several advantages depending upon the type of plate that is heated. It can also convey advantages to printers that want to make sure the plates will stand up under demanding press conditions.

 

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