Whiteprint

Whiteprint describes document reproduction using the diazo chemical process. It is also known as the blue-line process. It is a contact printing process which accurately reproduces the original in size, but cannot reproduce continuous tones or colors. The light-sensitivity of the chemicals used was known in the 1890s and several related printing processes were patented at that time. Whiteprinting replaced the blueprint process in reproducing architect's and engineer's drawings, because the process was simpler, and involved fewer toxic chemicals. A blue-line print is not permanent and will fade if exposed to light for weeks or months, but for many purposes a drawing print that lasts only a few months is sufficient.