The truth is dry cleaning is not entirely dry. Dry cleaners do apply liquids to silk dresses, it’s just that the stuff contains no water and furthermore dries quite rapidly. It doesn’t cause clothes to shrink or colors to run.
Routine dry cleaning is done in large, closed machines using a volatile chemical called perchloroethylene (C2C14), dubbed “perk” in the trade. Perk is a compound consisting mostly of chlorine, with a lesser part of carbon.
As clothes are agitated in a machine, perk, along with a detergent, passes through the machine at a rate of two thousand gallons an hour. About every minute there’s a new batch of perk running through the clothes, dissolving stains and leaving dirt stranded in a filter. After this process most clothes are ready to be pressed and bagged.
The meticulous dry cleaner may, however, spy a stain that withstood the perk and need to apply the finer skills of his trade.
The first step, a crucial one, is to analyze and identify the stain. Many are unknown; a large proportion, called “sweet stains,” contain sugar, salt or starch and come from spilled food. The spotter then selects from four standard methods of stain removal and goes to work at his spotting board. He may dissolve the stain with the appropriate solvent, such as volatile-type paint remover, hydrocarbons, or petroleum distillates.
Legend has it that the dry-cleaning industry originated with a Frenchman in the nineteenth century who accidentally doused his clothes with benzene and subsequently found grease stains easy to get out. If the stain is water soluble, the spotter can just blast it with his steam gun and blow it dry.
Another approach is to apply a lubricant with a stiff brush or spatula and try to raise the stain to the surface of the fabric, where it can be removed more easily. If that tactic fails, the spotter may resort to chemical action: he applies an oxidizing bleach that removes the color from the stain and so camouflages it; or he converts the stain using acids or alkalis into a soluble substance that can be treated with solvents.
The very last method is to digest the stain with enzymes, just as your gastrointestinal enzymes break down insoluble protein, albumin, and starches. The enzymes, which are from bacteria and yeast, convert insoluble substances into soluble ones that can be cleaned away quite easily.
The spotter, then, has an array of methods and chemicals at his fingertips, so you needn’t despair when salad dressing drips down your tie. Just remember what you spilled, and half the battle is won.