Hot Water Rinses
Were normal and indeed required when using soap for wash day.
Soap is very difficult to rinse out of laundry, and housewives were advised to always have the rinse water either hot or at least warm when using a hot water/soap wash. Of course those doing laundry by hand in a tub couldn't use too hot water, but machine washing was another story.
Purpose of all this palaver is that cold water causes textile fibers to contract. If this happens with soap, all that soap/scum/soils would become "trapped" in the wash, making it that much more difficult to remove. The end result over time would be tattle-tale grey laundry, something no respecting housewive would dare hang on her wash line. Well, not if she didn't wish to become the object of stares! *LOL*
L.