This is the fifth in a series of articles on synthetic fibers and how they relate to shaving brushes, including a brief history of synthetic fibers, their development, stagnation, and resurrection in the market place. In the previous article, the discussion was based on how a new product which was canned shaving cream virtually eliminated all requirements for synthetic brushes and severely reduced the demand for shaving brushes from an overall requirement for all shavers to a very small segment of the overall shaving public.
From the perspective of the traditional shaver, almost everyone had gone to the new canned lather and there would be very few choices for brushes based on that dramatically reduced demand. The great traditional natural brush makers in Europe would have the remaining market mostly to themselves for many years to come. Synthetic brushes would simply go away except for a few limited options, or would they?
At this point the question comes back to what requirements, or market forces, would be in place to cause the development of more sophisticated synthetic fibers? Remember that the old Nylon filaments were barely better than glorified fishing line in many respects. The answer was the painting industry, and the driver was new paints that forced an obsolescence issue with hog hair bristles. This situation is discussed as follows from an article on painting:
“Once upon a time, the finest paint brushes were only made from hogs hair imported from China. This was true for a number of years until the advent of latex paint. The standard China bristle brush did not hold up well with the new latex paints, and the hog bristle had become harder to acquire, so manufactures put their R&D departments to work in an effort to develop a synthetic bristle for brushes that would work better with the new latex paints. Trial and error and new developments have led to the filaments of today’s synthetic bristle brushes.
The early synthetic brushes were poor copies of the natural hog bristle brushes, but with time the manufacturers developed a way to flag (split the ends) the bristles, combine bristles of differing lengths and stiffness which gave the brushes a better taper and feel. Today, synthetic bristle brushes are very good copies of the natural hog hair bristles long used exclusively for the best paint brushes.” 
It sounds like the beginning of bed time story at first, but the point is clear. Over the period of many years paint brush manufacturers worked on developing variation after variation of materials, fiber cast patterns, tip separation (flagging), etc. In fact the pattern of the fiber itself and the flagging of the tips would be very important in the development of synthetic bristles. Flagging is the technique that “explodes” the filament and so that it applied liquids smoothly with no stiffness at the tip. 
Each successive generation of synthetic paint brushes brought in new developments in Nylon and Polyester materials that would be able to stand up to the rigors of paints, thinners and cleaning solvents. The DuPont Corporation led the way in developing many of these variations of synthetic fibers under a variety of names such as: Tynex®, Orel® and Chinex®.  Many patents were taken concerning the development of various methods of developing fibers, as seen in the photo of the synthetic paint brush and an associated patent. 
At this point DuPont was in the drivers seat in terms of synthetic fiber manufacturing throughout the decade of 1970 and into the early years of the next decade. However in Japan a company called Toray would begin to make inroads into to the synthetic fiber market. In 1964 Toray Started production of TORAYLON® acrylic fiber and production of SILLOOK® silk-like polyester filament. In 1966 Toray started production of PROMILAN® Nylon 66 fiber.  Nylon, Polyester, and another yet to be discussed fiber would have a prominent role in another area of business that continued the development of synthetic fibers that would eventually be used to provide new opportunities to the makers of synthetic brushes. The existence of synthetic materials alone would not get the job done and a new set of structural designs would be necessary to allow synthetic fibers to begin to handle the complex job of controlled applications. This will be discussed in future installments of this series.
 U.S. Patent number: 3706111 Filing date: Aug 21, 1970 Issue date: 1972