When buying a suit or ordering a made to measure one you encounter the ‘S’ symbol proceeded with numbers that marques the wool. What does it stand for and how should you interpret it?
The markings 100’s, 110’s, 120’s relate to wool that is used in confection of formal wear like suits, coats, waistcoats etc. These figures do not refer to the twist rate of the yarn, but to the diameter of the fibres used to manufacture the woollen yarn. The higher the number for ‘S’, the thinner the fibre. Let us see how this measurement system was invented.
In the past, this ‘S’ parameter was defined in such a way that it was checked how many 590 yards long hanks (skeins - thus the letter ‘S’) could be obtained from one pound of raw wool. The thinner the raw wool fibres, the more skeins could be obtained. For example, if 80 skeins were wound from a pound of raw wool, it was wool with the 80’s parameter, and if there were 150 skeins, then the wool was given the 150’s symbol.
The old numbering is still used today, but it refers to the fibre diameter of the yarn (measured in micrometres, or thousandths of a millimetre). It is formalised by the IWTO – International Wool Textile Organisation that organises the different wools produced around the world. Super's are therefore an integral part of a precise measuring system.
A classification of Super ‘S’ in micrometres:
* interesting fact, the diameter of human hair may range from 17 to 181 μ
How to apply this knowledge in practice? Well, the thinner the wool fibre, the more delicate and creasing the wool becomes. If you are looking for an everyday suit that can be worn frequently, go for wool from the 100's to the 130's. Wools over 140’s are more delicate, shinier and rather suitable for special occasions or for summer suits.
Obviously, the thinner the yarn fibre, the more expensive the wool. This is because obtaining this type of raw material is very difficult and requires very careful or even selective sheep breeding. Only a few drapers are capable of producing such exquisite wool and we can mention Loro Piana, Ermenegildo Zegna or Kiton.
Another point that should be taken into account when choosing a fabric is its weight, i.e. how many grams of yarn per square metre. 120’s wool can for example appear in the weight of 230 g and then its application will be mainly for summer suits but also in 380 g for winter clothing.
As you can see, there are a lot of factors deciding which wool to choose. It is also important how you will use your suit - whether it is a formal outfit for special occasions or for everyday wear. Hence, it is very important to consult your choice with a tailor.