Over the course of time, designers have used different supports, which vary depending on the time period:
- Paper: used to create originals but also to make copies.
- Natural tracing paper: appearing in the mid-XIXth century, it was produced by extreme refining of paper pulp. It becomes fragile as it ages and tends to yellow.
- Chemical tracing paper: a process invented in 1858 (immersion in sulfuric acid), it was replaced in the 1930s by progress in natural tracing paper. Supple and sturdy, it kept well if the rinse was done properly.
- Polyester (Mylar™): developed starting in 1955, its great flexibility and excellent stability over time made it the benchmark support until the advent of computer-assisted design.
For exchanging information, copies of plans were used in the form of prints but also microforms:
- Cyanotype prints: more commonly known as “blueprints”, they came into use starting in 1870. It was a three-stage process: sensitization in a bath, exposure to light under an original, and finally development in water.
- Van Dyke proofs: invented in the late XIXth century, they use the same manufacturing process as blueprints, with different products and an additional bath (image fixer). This process produces a print with white lines on a brown background.
- Diazotypes: in common use starting in 1920, the ammonia-based process makes them easy to identify. The print, which can be on paper or tracing paper, is characterized by a brown, blue, or purple line on a white background. All these prints are very light-sensitive. They are stored away from other documents, to prevent any chemical reaction.
- Microfilms: invented in the mid- XIXth century, they save a great deal of room. Generally in the form of silver-film strips, they have a long lifespan in good conservation conditions, which makes them a widely used format.
- Perforated cards: they came into use in the 1960s. The perforation system made it possible to sort them mechanically and it’s easy to make inexpensive copies on a diazo-compound support. In the 1970s, they were replaced by IBM-style aperture cards.
- Microfiches: in use starting in the early XXth century, these are rectangular sheets of film, containing several images. An extremely compact format, reading them requires a magnification device.