Figuring It Out by Nuno Crato

Author:Nuno Crato
Language: eng
Format: epub
Publisher: Springer Berlin Heidelberg, Berlin, Heidelberg

This standard also makes it simple to calculate the weight of a ream of paper, for example. The weight of the paper, or “grammage” as the professionals say, is calculated in grams per square meter. Normally we might use paper that weighs 80 g/m2. This means that one A0 sheet of this paper weighs 80 g. As one A0 sheet has the same surface area as 16 A4 sheets, each A4 sheet weighs 5 g and the whole ream (500 sheets) of A4 paper weighs 2500 g or 2.5 kg (approximately 5 pounds 8 ounces).

The system defined by the ISO 216 standard also encompasses two other series of sizes. These are the B series, used for envelopes that contain the equivalent sheets of paper from the A series, and the C series, used for slightly smaller envelopes that may contain fewer sheets of paper. For example, if you need an envelope to mail an A4 brochure, you can use a B4 envelope, which measures 250 × 353 mm (almost 10 × 14 in.). If you want to mail a thin A4 document, you could use a C4 envelope, which measures 229 × 324 mm (about 9 × 12¾ in.). This makes it simple for retailers to know what their customers need.

But the exact dimensions of the envelopes are also mathematically logical. The geometrical mean between two consecutive A sizes was used to define the dimensions of the B series. For example, the geometrical mean between the dimensions of A4 and A3 paper was used to calculate the dimensions of a B4 envelope. A similar procedure was also used to calculate the C series, so that the C4 envelope is defined by the geometrical mean between the A4 and B4 sizes.

The geometrical mean is a mean, as a pedant would state, that results in intermediate dimensions between extreme values. But it is a special mean. It is obtained from the square root of the products of two values. That is why it maintains the relative proportions. So B4 is to A4 as A3 is to B4.

This whole complex system evolved over a period of two hundred years, and finally it was adopted almost all over the world. As far as we know, the first person to think of standardizing paper sizes using similar rules was a German professor of physics called Georg Christoph Lichtenberg (1742–1799). In a letter he wrote in 1786 to his friend Johann Beckmann, he described the aesthetic and practical advantages of using paper with a length to width ratio of one to the square root of two. With regard to the practical advantages he was certainly right, but opinions are divided about the aesthetic aspects. Graphic designers know that the A4 system is not aesthetically advantageous for placards or magazines—it is not used for the advertising posters you see in the streets or for magazines. This is one of the reasons why Americans do not want to abandon their good-looking letter format (8 × 11 in.) that they have been using for many years.

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