@stan
Just wanted to point out the obvious about using chlorine bleach for pre-treating stains. Would never suggest that you made such a recommendation. *LOL*
In general:
Pre-treatment products are still needed and used for domestic laundry for same reasons in commercial, they have a place. Better laundries like dry cleaners attend to spots before and or after the cleaning process. Lower quality places do not and you can often see the results. Sending an order of badly stained laundry to the former likely means it will return in various states from totally stain free to looking like something the cat dragged in.
Pre-treatment products often contain surfactants and or lubricants which help ease stains out of fabrics. Glycerin, Banana Oil, and so forth are employed for this purpose.
Why we pre-soak:
In early days soaking was done (usually in water make alkaline by various substances) to help break soils from fabrics and thus lessen the work of doing wash by hand. It also helped loosen soils/stains that would be set by routine use of soaps and hot to boiling water laundering of the day.
As mechanical washing machines became more common pre-soaking became less necessary. Pre-washing in cold or warm water for a short period of time would achieve the same results with less work than soaking.
Then came enzymes...
Enzymes are the only "living" part of modern laundry products. Once activated the little guys will continue to act upon (digest) whatever their food (protein, lipids, starches, fruits, etc...) happen to be until there is nothing left. Better still they will make more of themselves to continue that process long as conditions are optimal. For this reason products contain only small amounts of enzymes in relation to other substances in a formula.
Beauty of enzyme soaks is that the action continues for as long as one wishes. This is why again soaking items that are badly stained will get you where you need to go if done properly and goes on long enough.
Soaking with oxygen bleach;
All oxygen bleaches will work in cooler water temps, it just that the contact time must be lengthened. However we can make that gentleness work to our favor. Fine linen tablecloth of lace that could be damaged by boil washing with oxygen bleach can be soaked to whiten and remove stains using hydrogen peroxide (liquid) or powdered oxygen bleaches.
Key here is two things. First never, ever, ever soak for prolonged periods of time with oxygen bleaches using a metal container. Just don't do it. The released oxygen reacts with metal to form small bubbles which is all fine and well as that enhances cleaning/stain removal. However if it goes on too long and in one area you will get textile damage. That is holes and rents/weakened areas. In a washing machine water and textiles are in motion which dilutes this reaction even though the tubs are metal.
Plastic tubs are fine for such soaking as enamel over metal as long as there aren't any chips exposing the base metal. I have several NOS large diaper pails used for soaking and nothing else. This way one can keep them from developing chips or gouges.
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