Controlled felting (also known as “milling” or “fulling” in the USA is a finishing treatment for wool – first used by the Romans - to achieve a number of desirable effects including increased thickness, reduced air permeability and increased strength. It can also be used to produce the “blind” finish required for applications such as billiard cloths.

Interlocking scales

The surface of a Merino fibre has microscopic scales that can interlock with the scales of adjacent fibres. Under certain conditions, these fibres will move in one direction, but not the other – an effect known as “ratcheting”. If uncontrolled, this can sometimes produce undesirable results (e.g. shrinkage) but it is a characteristic that can be used to produce fabrics that are warmer, stronger and more aesthetically pleasing.

Two thousand years of felting

The Romans were known to exploit the fact that wool progressively entangles when masses of the fibre are subjected to repeated mechanical force, beating moist wool in vast vats to produce superior fabrics for their soldiers. Controlled felting has been used in the two thousand years since to improve the serviceability of cloths and, though it’s a simple operation, can produce a wide range of useful effects.

Warmer wool

A common objective of controlled felting is to increase the thickness of a fabric or make it “fuller”. This reduces air permeability, and makes it warmer for use in garments such as overcoats and outerwear.

Stronger wool

Another purpose of controlled felting is to shrink or consolidate the fabric to increase strength. This increased strength is the result of the scales of the fibre interlocking. It is possible to create a fabric that doesn’t have the cover required for serviceable use, but to then employ controlled felting to develop the strength of the fabric to the level necessary for end-product use.

Blind finish for billiards

Controlled felting raises fibre to the fabric surface and obscures the weave in a way that can be desirable for aesthetic or practical reasons. The blind finish required for certain coats and billiard cloths can be obtained by first felting, and then raising and cropping.

Softening handle

After setting and scouring, many worsted fabrics are too harsh, crisp or firm for their intended garment use. Controlled felting can be used in these circumstances to soften the handle and so greatly enhance their desirability and comfort for the wearer. This is known as “cracking”, “bursting” or “developing”.

Summary

Controlled felting – also known as milling or fulling – exploits the fact that wool becomes progressively entangled when subjected to repeated mechanical action. Caused by the interlocking of the microscopic scales on the surface of the fibre, it is a finishing treatment used to create a wide range of desirable effects including increased warmth, softer handle, and blind finish for use in a range of applications including billiard clothes.

References:

• Chapter 12 “Milling, fulling and fabric development” by Allan De Boos, in Textile Finishing (ed. Derek Heywood), Society of dyers and colourists, Bradford, UK, 2003