Detachable collars both stiff and soft faded out of daily men's fashions by the 1930's or 1940's. Some men still wore them (and still do) but this is largely either a die core group of fashion sort. Then again "stiff collars" are still part of many men's formal evening wear or say for special events like a wedding. In places like the UK they are part of the traditional "uniform" for barristers, judges, etc... Indeed one of the few if not only places left that still has the equipment to launder, starch, and iron stiff collars is in London:
http://www.barkergroup.info/barker_collars.html
http://www.dailymail.co.uk/news/art...oom-demand-producing-80-000-collars-year.html
Elsewhere such collar ironing and other specialized machines were long ago scrapped.
However you can still find side loading H-axis washing machines including pocket units that are fifty or more years old chugging away. While newer offerings can extract, there are still those in operation that do just one thing; wash/rinse. Soaking wet laundry must be moved to an extractor:
http://www.ebay.com/itm/Commercial-...879182?hash=item282257ebce:g:noQAAOSw8gVX~Eoo
Because the washers shown in OP didn't extract, starching was done in another machine department. Smaller laundries could get away with returning the wash to same machine or another after extracting to starch, but large plants like this had to keep things moving. Rather than tie up the "washing" machines there was another that did starching and it varied by what was being processed. There were actually machines that starched just stiff collars, shirt bosoms, etc... This was to replace the slower work of hand starching.
Stiff collars and bosomed shirts are an art. You have to get the starch into the fabric but not just on the surface. In the case of shirt bosoms only that part and maybe the cuffs and neck band were starched. Thus obviously you couldn't put the entire shirt into a starch bath. Again this was often done by hand in the domestic setting or small laundry. A place like the "Palace Laundry" shown above that did hundreds if not thousands of stiff collars per week required faster through put .
Final bit of trivia: the detachable shirt collar was invented by a woman. Tired of laundering her husband's shirts when only the collar was dirty it came to her why not have the two separate.
https://en.wikipedia.org/wiki/Detachable_collar
Troy, New York became known as the "collar capital" of the USA. Not only did the place produce much of the inventory, but many laundries that specialized in cleaning and starching said garment were located there as well. You simply packed up your dirty collars and mailed them (in a small box), and clean ones came back via same.
Due to hygiene habits being what they often were then, and the expense of having collars laundered many men wore the same one more than once, sometimes for a week or longer. As you can imagine by the time the things went to the wash it suffered a major case of "ring around the collar". Hence all the scrubbing, hot water and so forth you see in above clips. It would have involved a heavy dosage of bleaching and bluing to counteract the yellowing that came from built up collar soils. Because the industrial laundering process was so harsh many did tend to wear things longer between cleaning to help preserve. [this post was last edited: 10/16/2016-16:07]