The word ‘squeeze’ sounds like one of those passwords that are used by the printing world simply to add to the mystique of letterpress. It’s true that it has been used in the past by some printers to justify some very imprecise practices. That said, squeeze is something for printers to think about, especially those concerned with precision.
After World War II the general drive for greater productivity and quality meant printers needed to adopt ever more precise ways of working to avoid problems during printing and also increase the productive hours of each machine. Where once objects like furniture and blocks could be points adrift from their stated size, they now had to be correct.
‘Squeeze’ is the term to describe the difference between the length of a line of type as sat in the composing stick; and the same line when locked up in a chase ready to print. The accepted view was that a compositor should set type a little longer than the measure (line length) but the forces of quoins would squeeze the type together and bring it back to the intended size.
Knowing that type metal itself cannot usually be compressed, we have to look at what else could cause this phenomena –
- Dirt and other deposits on the walls of type might be compressible
- Bent spaces might be brought back in to true
- Type that is not straight in the stick (‘off its feet’) may be corrected to an upright position
- Basic equipment, like the composing stick, might be inaccurate
It follows, then, that if clean new type is used in an accurately made and set composing stick and the line is properly justified then there is no room at all for compression and so squeeze is eliminated. Remember that the pressure of the quoins on the specific lines will be around the same as the pressure of the composing stick ends.
The problem then becomes ‘how can the line be accurately filled’, for the endless combinations of character widths and standard spaces will always leave some room at the end of a line. As an example, a line of 14pt type is set and a gap at the end of the line is too small to be filled with a thick space, and too big to be filled with a middle space. The difference between the two is 1 and 1⁄6 of one point.
Naturally spaces cannot be made in each possible size, so if we are using the precision approach above every line will be short because an irregular space will exist at the end of each line. Our answer now is to make sure that, on average, each line is correct.
To do this we have to establish a common space: what is the average difference between any two standard sizes of space. Just how big is the jump between mid and thick; or thin to mid; or mid + thin to nut?
Saving you the maths, the answer is 7/120ths of an em, and converting this to points the average is 7⁄12th of a point. That is to say that any given combination of type and standard spacing will be between 7⁄24th over line length and 7⁄24th under line length. We have to further round this to a usable unit, and the key point is to set your composing stick to ½pt over the desired line length.
To make the best of this, the following points should be observed –
- Composing sticks should be periodically checked for accuracy
- Precision, milled, em gauges should be used to set the stick along with a half-point gauge. All sticks should be set from the same gauges
- When using type over 14pt, use half-point ‘hair’ spaces
- Leads should be cut to the line length minus one point
- Reglet should be used down the sides to pages to take any remaining irregularity in justification