Green, environmentally-preferred, sustainable, biobased, safe — the terms are sometimes used interchangeably. However, their meaning and interpretation really depend on one’s viewpoint.

The following thoughts on green cleaning represent my viewpoint. I did, after all, volunteer to write this article; and, at this point I have been involved in precision and industrial cleaning activities for decades.

GREEN EVOLUTION
My own view of green cleaning has evolved; and will no doubt continue to change. About a generation ago, I became involved in (“was coerced into” might be a more apt description) industrial and precision cleaning as a consequence of the move away from ozone depleting chemicals, specifically CFC-113 (chlorofluorocarbon 113, popularly known under the trade names Freon or Genesolv) and TCA (1,1,1- trichloroethane). Both were considered relatively benign to workers; they were inexpensive, plentiful, and widely used in industry. Unfortunately, given their molecular stability, they reach the stratosphere, releasing chlorine free radicals that destroy the protective ozone layer.

Both were phased out of production under the Montreal Protocol; the phase-out presented an acute problem for industry. Typical precision or critical cleaning processes were straightforward; processes depended on repeated spraying, ultrasonic cleaning, and vapor phase degreasing with CFC-113 and/or TCA. Perhaps a bit of isopropyl alcohol might be used; a final rinse/drying step in acetone was popular. Aqueous cleaning was often consigned to industrial, rather than critical, cleaning applications.

As the availability of CFC-113 and TCA decreased and the costs increased, a wide variety of aqueous and solvent based cleaning chemistries became available. So-called “non-chemical” cleaning such as CO₂ snow and plasma cleaning were considered. It gradually dawned on many in manufacturing that cleaning is not a chemical, it is a process. In electronics, water-washable and so-called “no-clean” fluxes were introduced. Cleaning processes were tested and validated; crucial customer requirements were met; irrelevant customer requirements were negotiated away. The manufacturing world did not wither and die; it thrived.