Our information about production methods for Spanish Civil War posters comes mainly from Carles Fontsere, the Catalan artist who was active in the Union of Professional Artists (Sindicato de Dibujantes Profesionales) in Barcelona. As he describes the process, a poster artist typically painted in water colors on moistened paper stretched across a frame. The verbal text was also painted by hand. In most cases, after the original poster was painted, a lithographer copied each color onto a separate zinc plate for printing. Some of the artists, however, including Fontsere, worked directly on the zinc plates themselves. The requirement for multiple plates worked against the use of too many colors; three or four was typical, five or six unusual.

A number of other material constraints also affected the posters. First, they had to be clearly visible from a distance in order to be effective in public sites, including outdoor locations. Second, the use of water colors made it impractical to overpaint with light colors over dark ones. Instead, poster artists often used the white of the paper itself as a major design element. Finally, the paper used was generally the least expensive, often a form of newsprint. The largest number of posters were about 30 inches wide and forty inches high, though double-sized posters, printed on two sheets of this size and glued together were not uncommon, and some substantially larger posters were produced. Many posters were printed in runs of 5,000 or 10,000 copies, enough to guarantee wide distribution and visibility. The cities of Barcelona, Madrid, and Valencia each had two or more large poster workshops working continually. Usually a given workshop specialized in posters for a particular political group or coalition of groups.

Variations on the primary pattern included a number of small posters printed by photo-chromolithography on high quality paper and sold in streetside stalls, offices, and bookstores. Drawings and lithographs were also issued in more limited editions on heavy stock for sale to individual buyers. And some posters needed for immediate use in a particular place were done as unique paintings, sometimes in oil. Like similar workshops in Madrid and Valencia, the Sindicato also produced banners and placards. The banners were painted directly on primed cotton whenever it could be obtained.

A great many posters were also reprinted as postcards, sometimes many months later, so that a given image often received a second life and a second means of distribution. A considerable number of postcards were also independently designed and never appeared as posters. From time to time sets of ten postcards were sold in illustrated packets. Many thousands of such cards were sent home by international soldiers, journalists, and other visitors to Spain. Finally, small decorative stamps in substantial numbers over a thousand different ones during the course of the war’s were issued as miniature posters. Some reproduced large poster designs, but many represent independent works of art.

Fontsere has called the posters the “certificate” of the social revolution that formed in response to the generals’ attempted coup: “each union, each small committee, came out with its poster; each profession, each trade – barbers, taxi drivers, tram conductors – could be seen in a poster breaking the bonds that oppressed them.”