Heated Indoor Drying via Racks:
Was a way for the housewive or launderess/maid to do wash independent of the weather. Until tumble dryers were invented wash was hung on clothes lines out of doors, however this required fresh air and warm sunny weather (a light breeze wouldn't hurt either). Indeed many women woke up and seeing the weather would think to themselves "this is fine day to do laundry". OTHO the reverse was true, if wash day was Monday, and it was cloudy and or rainy or other bad weather the wash normally was put off.
Drying laundry indoors however was often done, either via airing cupboards, racks/lines in the attic or in the kitchen. The later especially where homes on both sides of the pond had those huge AGA type ranges. Such ranges gave off more than enough heat to dry laundry and racks were often suspeneded over them. However this sort of drying meant one shouldn't cook anything with a powerful scent such as fish for the duration. It also could mean hoovering under dripping laundry while the stuff dried.
Indoor drying was frowned upon because in the era of soaps as the primary laundry "detergent", whites could develop a dull yellow cast when not dried outside in fresh air.
The Vanderblit Biltmore estate has one of these vintage indoor drying systems as part of their laundry. It is original to the estate and one can peek during tours.
Boiling Laundry:
Boiling wash was done on both sides of the pond in some areas right up until the 1950's. As washing machines gradually replaced manual labour for doing laundry, the need to boil was replaced. Indeed have housekeeping and laundry manuals from the 1940's that cleary state if a woman had a washing machine, she did not and should not boil laundry as part of her normal routine.
Contrary to popular belief, boiling was not a way of mainly cleaning laundry, but a second or third "wash" after an initial cold or warm pre-wash/soak, then soaping, rubbing, and so forth. The purpose of boiling was several fold: first it helped shift soils/stains that didn't respond to the initial washing and treatments.This meant less hard scrubbing and rubbing which was easier on textiles. Boiling itself is hard on textiles, but not as much as beating, rubbing and other mechanical methods.
Boiling was also a way of removing the soap which was the primary detergent, from textiles. As the water temperature increased the fibers of the cloth relaxes and opens up, this causes soils, muck, and whatever else that is trapped or on the textile to be released. This is one of the reasons boiling washes were followed by one or two hot or at least warm rinses. You want to keep the fabric "open" to flush out the gunk you just boiled away. Cold water would caues fibers to shut down quickly trapping the muck right back where it came from.