Before inkjet became the dominant printing process, screen printing was the only segment in the world of printing that could and does print on practically anything. During this time, most printing was done on some form of paper, where adhesion and durability were not primary factors in ink and substrate performance. The commercial screen printing industry began as a short-run process to reproduce images on paper and paper board substrates.
Sign companies adopted screen printing because it allowed them to use the same enamel paints they used on metal and wood substrates to create durable exterior graphics or signs in multiple quantities to supplement a product line of one-off handpainted signs. Even though these signs were printed and not brush painted, they were expected to have the same exterior durability. This was the beginning of the durable graphics market in printing.
The real monumental change took place in the 1950s, when plastics became available and affordable for signage. The plastics industry developed and plastics began to be used in every application imaginable. As soon as products were made out of plastics, there was a need to imprint functional and decorative images on the plastics. This led to the need for different inks. Inks for plastics all needed to adhere to plastics, but while some needed to be rigid on certain plastics, and others needed to be highly flexible. Some products required abrasion resistance, some chemical resistance, and some resistance to nuclear blasts (an infrequent request for Nazdar). After 50 or more years, we have a screen printing ink industry where there are 30 to 40 different types of inks made by several ink manufacturers in an effort to meet all these needs.