4 My introduction to lithography at work and college

While I was at college we were required to learn about all types of printing however some of the processes were only learnt by theory and not practical. Because I was only able to operate letterpress in-house the chance to learn lithography appealed to me and as such took more of an interest in the process, from black and white, to colour and the separation of full colour dummy jobs at college. I could see that the lithography would be fantastic at printing jobs from a flat plate rather than raised type as on letterpress (raised type at the height of 0.918 inch, or 23.3172 mm). I progressed well at college learning lithography and whilst still learning work bought a Heidelberg Tok, which was an offset printing press, although still in the lithography category the press it doesn’t have a separate damping system, but with integrated damping. It is capable of printing on a sheet size of just over A4 size, probably SRA4. The sheet per hour is anything of 1500 to 10000, but reliably perfect probably no more than 7000, or 8000. The front view is here. The left side is here.

The Tok was very easy once all of the various settings and tweaks had been taken on board. On the presses there are various tweaks and settings that are available, some of which an engineer would only know. We were lucky enough to have an ex-Heidelberg engineer who had setup his own business and was well in the know of settings of all sides of the press. So as a result of this I was able to completely dismantle and set the whole thing including all the roller pressures as each roller has different settings. As time went on I was in the predicament of being able to run a Tok in the jobbing world in daily production of all matter of stationery.

Whilst at college during my apprenticeship, college purchased a Tok and knew that I was well up on it. As such I was asked to introduce and teach others in the class, just as others had done with pupils on presses which were alien to others in the group. The machine at work was a new machine, a new process at the time and training was done over a few days with official Heidelberg engineers/operators. The lithographic press that I learnt at college was a Heidelberg GTO and it was this press that gave me the confidence to want to learn lithography. This machine has proper registration with the paper, where the paper is fed down an inclined surface to adjustable registration pins followed by gripper bars. At the same time an adjustable left registration side bar moves very slowly from either right to left or vice versa, depending on which side is the best to use, which makes it possible to finely position the sheet just before the front guiders release the paper into the gripper bars. This movement is performed every time a sheet is fed through the press and it is very accurate to fractions of millimetres. Below is a picture of a Heidelberg GTO.

This press can handle paper size of up to A3 sheet size. It is a two colour press which uses only one blanket, whilst having two damper sections and two different inking systems. The average reliable speed is around 2000 to 3000 sheets per hour. The only thing with this type of two colour printing is that the damper settings on both plates must be perfect damper and inking settings as it is very easy to flood one of the two systems which causes massive stretch and over wet paper. You cannot over dampen as the paper stretches and becomes wavy and wrinkled rather than flat and wrinkle free and if the job has to go through another process at the customers, for example, photo copied, or ink jet printed then the paper may not respond as it should - due to paper being desensitization.