Whiteprint

Two components underpin diazo printing:[2] In a related sense, the process relies on two properties of diazonium compounds: In a variety of combinations and strengths, these two chemicals are mixed in water and coated onto paper.

The first is the exposure area, where the sandwich of the two sheets (the master and the diazo paper) passes in front of an ultraviolet lamp.

A slight delay of perhaps five minutes is often required for the fumes to subside enough to permit making additional copies if no ventilation exists.

Repeated lack of contrast and light prints is also a tip-off that the operator needs to adjust the speed or amount of ammonia.

This fading process thus requires reduplication of the original documents every few months in a typical office for any project using bluelines.

Incandescent lighting was often used in areas where blueline engineering prints needed to be posted on a wall for long periods to hinder rapid fading.

Improperly exposed bluelines are more likely to fade at an increased rate since the chemical reaction in the ammonia phase continues until the process is completed.

The cost of blueline production materials and equipment, the fact that the prints themselves faded in sunlight, and the need to use the pungent chemical ammonia as a developer sped up its replacement.