Steve Firth wrote:
Stuart Noble wrote:

Sugar soap is really designed to remove grease and other alkali soluble
gunk, and I don't think many of us live like that nowadays.

Most of what sticks dirt togther is grease of some form or another.
Either from human skin or often from trace quantities in the air (or
large quantities if one lives in diesel-soaked London.).

Interesting that sugar is quite a good abrasive, as is bicarbonate of
soda, but nothing IME makes the job any easier

I don't know if you are random word associating

I have nothing better to do

, but sugar soap has
nothing to do with sugar.

Sugar with soap (or washing up liquid)is a damned fine hand cleaner as
it happens, and it's reasonable to suppose its abrasive qualities were
not unknown to decorators. Then again, maybe someone just decided "sugar
soap" was a great name for something that had nothing to do with sugar.

And bicarbonate of soda works pretty much like
sugar soap in that it will solubilise lipids.

I believe sugar soap is now based on a fairly insipid detergent rather
than the phosphates it used to consist of.
Bicarb is sparingly soluble in water, hence its effectiveness as a mild
abrasive in a paste.