A brief history of synthetic filaments for paintbrushes. From the first filaments developed in the United States in the 1950s to modern alternatives to natural hair, the evolution of synthetic materials has profoundly transformed the brush industry.

The first synthetic filaments

The first synthetic filaments for paintbrush manufacturing were developed by DuPont in the United States in the 1950s, primarily for the decorating industry. Their development received a significant boost from the US ban on imports of Chinese bristles.

The main filament used was nylon (under the Tynex brand), which was extruded, mechanically tapered and then tipped and flagged to resemble hog bristle.

Nylon is still widely used in paintbrushes today. However, for professional artist brushes and cosmetic brushes, this filament is not a good alternative to natural hair because it is too stiff and does not have fine tips.

The breakthrough of polyester filaments

The breakthrough for the artist brush market came in the 1970s, when DuPont found a way to chemically taper polyester filaments. However, because the market was considered too small, DuPont sold the patent to Japan's Toray Industries.

Toray developed the process with input from Japanese brush manufacturers, particularly Takamoto, which used its Taklon brand. At the time, the only other company producing chemically tapered filaments was Teijin. As its filament was slightly different, it did not infringe Toray's patent rights.

In the 1980s, Toray licensed the patent to the Korean company Kolon, but once the patent expired in the 1990s, many other companies began production.

There are various types of polyester filaments, but PBT (polybutylene terephthalate) is the most widely used for professional artist brushes, while PET (polyethylene terephthalate) is used for standard brushes. The two raw polymers can also be blended to achieve greater softness than PET alone while reducing the cost of the product, as PET is considerably less expensive than PBT.

The search for alternatives to natural hair

In recent years, the industry has become increasingly involved in the use of synthetic materials, as many customers consider synthetic materials more hygienic than animal hair and more acceptable from an ethical perspective.

Professional artist brushes must be capable of applying a wide range of substances, from very wet to relatively dry media, which has made animal hair difficult to replicate.

Today, many characteristics can be incorporated into synthetic materials, including different diameters, taper ratios, crimps and hollows. However, animal hairs have certain characteristics that still make their complete reproduction difficult.

The challenge of Kolinsky

The real Holy Grail is to replicate Kolinsky sable, which has unique characteristics that make it the finest hair for use in professional artist brushes.

An artist looks for several characteristics in a brush:

• A fine point
• Point retention
• Colour/water holding and release
• Strength/snap
• Durability and control

Kolinsky is the only hair capable of providing all these characteristics, thanks to its unique structure. It has very fine cuticles along the hair shaft that control the pick-up and release of paint.

It also has a belly, meaning that the hair is fine at both the root and the tip. When the hair is inserted into the ferrule of a brush, the belly therefore sits in the centre, providing the necessary strength and snap.

It is now possible to produce synthetic fibres with scale-like surfaces, but many still consider natural Kolinsky hair unmatched.

Replicating the characteristics of different natural hairs

Many brush catalogues offer synthetic substitutes for different types of natural hair, including mongoose, badger, squirrel and hog bristle.

For example, to reproduce the appearance and characteristics of mongoose hair, the filament may be dyed five or six times to resemble its colour, while a larger diameter is used to reproduce the strength of the natural hair.

Larger-diameter synthetic brush filaments can reproduce the hollow core of natural mongoose hair. This acts as a reservoir for paint, although reproducing this cavity is more difficult in smaller diameters.

Replicating hog bristle

Another material that is not easy to imitate is hog bristle. The finest type of hog bristle comes from south-western China and is known as Chungking bristle.

It is very stiff and has fine flagged tips that make it particularly suitable for oil painting. To reproduce the characteristics of natural bristle, a large-diameter fibre is required, which must then be tapered or mechanically processed to split the tips.

The softness of squirrel hair

Squirrel hair is the softest of all the hairs used in brushes, and the challenge for filament manufacturers is to extrude a filament as fine as possible while still providing sufficient strength for brush manufacturing.

A very slight crimp is added during extrusion, together with antistatic agents to help the fine filament spread correctly. This creates a highly suitable alternative to squirrel hair.