Paper machine: the dry end
The watermarked paper is then subjected to a drying process in which it is wrapped around a series of steam heated metal cylinders known as dryer cylinders. Hence why we refer to this stage as the “Dry end” of the paper machine.
It may sound simple, but this stage is in fact incredibly complex. The pressure of the steam and the speed of the machine must be tightly controlled to ensure a gradual drying gradient down the machine that preserves the registration of the paper features whilst also achieving the correct end moisture for the finished paper.
Following an initial drying stage, the paper is then submerged into what is known as a ‘size press or bath’, where surface treatments, suitable for subsequent printing processes, are coated to the paper.
After the size press, the paper is fed though a second dryer section to dry the surface treatment.
The paper is then run through a set of smoothing cylinders, known universally as “calenders”. In this process the paper passes between two or more large rollers which are pressing against each other under high pressure. This process gives the paper its final desired thickness and smoothness.