The 3M Company was developing a new ink hardening system. Normally, inks dry by solvent evaporation or they are hardened with heat.

The new approach would use ultraviolet radiation. A small batch of blue ink was made up and run through the small UV processor in the lab. The resulting ink came out hard and had good adhesion to the aluminum test panels. Other tests confirmed that the ink properties were satisfactory. The batch was scaled up in a production run when they realized the UV was bleaching out the blue color so that the ink looked like a clear coating. 

But why didn’t this happen in the lab? 

The Rest Of The Story

It seems that the extra lamps and the additional ozone was enough to chemically modify the blue dye molecule to one that had no light absorption. Take note, scale-up can have surprises.