In another thread, angus was reminiscing about how "when all the phosphate nonsense started, Purex's Instant fels got a bit of a shot in the arm since it was a soap so could tout that it was a no phosphate product. But again it didn't do that well. Soap was more difficult to use and with the energy crisis almost upon us and everyone being exhorted to use cold water, that rendered soap for laundry pretty much useless."
I recently got a box of Instant Fels on fleabay and found angus was right.

I recently got a box of Instant Fels on fleabay and found angus was right.
