daniele capo

warning: this is not an how-to, read it more like some notes I take while I’m thinking about the problem of building a press.

In the first post I made some consideration about the art of making tools, what we can learn from matters and other nice things. Now my aim is to investigate the basic principle of a press.

Transferring ink

Basically the printing press is a device for transferring ink from the printing surface to paper (or other material to be printed) applying an even pressure on the whole surface. If the surface is small enough (for example, a stamp) you can easily apply the proper pressure with your own hands, otherwise you need to find another way.

One simple way, as I have observed, at least, is the principle used in japanese woodblock printing: you do not apply the pressure on the whole surface at the same time, but you distribute the pressure gradually with the baren.

Anyway we are in a ‘western’ context so we want to use the other approach, i.e. using a machine able to transfer the pressure all at once (and as you can understand this implies a really big pressure). The Gutemberg press, as far as I know, was built like the wine press: a big wooden screw. The printing surface and the sheet of paper was trapped between two solid, plain surfaces and you had to apply the pressure by means of the screw. First problem: the ‘plain surfaces’ have to be really plain. Second problem: it seems that the simple mechanics of the screw is unable to print large surfaces.

Using levers

Instead of using a screw (I wasn’t able to find one large enough) you can use a lever (as I did). The very basic approach is shown in the next image: applying a force at the end of the lever results in a multiplication of the force.

Of course you still have two kind of problem:

• big forces means hard materials
• the multiplication effect of a simple lever is unable to transform the force of only one man in the pressure needed

A lesson from medieval architects

A modified model is shown in the next image. The force is applied on the node, and transferred to the bars. The principle is similar to an arch (rotated by 90 degrees). As you know the arch always trasfer an horizontal pressure sideways (the reason why you always find an iron bar joining the imposts). In the case of our device you can use the ‘sideways’ forces to multiply your energy.

Traditionally we are taught that the ogive of gothic architecture was introduced to minimize the lateral forces produced by the arch (a very XIX century positivistic point of view). If you reverse the lesson you find that a flat arch would exert a bigger pressure.

Now you can see that when our rotated triangular arch becomes almost flat the decomposition of forces is such that the lateral pressure would be teoretically enormous. So, maybe, a better press can be built with this device.

In the next part I will discuss the problem you are likely to be faced with if you really want to do such a thing