thumb|Whiteprint plan copy. thumb|USSR whiteprints. 1970's. Whiteprint describes a document reproduction produced by using the diazo chemical process. It is also known as the blue-line process since the result is blue lines on a white background. It is a contact printing process that accurately reproduces a translucent original in size, but can reproduce only limited tonal range and no color.
thumb|Whiteprint plan copy. thumb|USSR whiteprints. 1970's. Whiteprint describes a document reproduction produced by using the diazo chemical process. It is also known as the blue-line process since the result is blue lines on a white background. It is a contact printing process that accurately reproduces a translucent original in size, but can reproduce only limited tonal range and no color.
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 for reproducing architectural and engineering drawings around the turn of the 20th century 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 a print that lasts only a few months was sufficient as a working drawing for many purposes, and the original vellum drawings could be stored and reprinted as needed. Whiteprinting became obsolete around the turn of the 21st Century as technical drawing was replaced by computer-aided design and thus digital pen plotters or large-format printers (still sometimes colloquially called "blueprint printers") became favored.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).