I think I remember these packets of "foaming bath seeds".
I think the outer paper packet had a plastic packet inside and you used half that packet at a time. You might think it would be easier to have two smaller inside packets perhaps, but they didn't. Just thinking about this reminds me of the bathroom in my mother's house with fish and flower transfers on the tiles, fish patterned fablon (sticky back plastic) on the panel along the side of the bath, and initially, at least, fish patterned black towelling curtains.
I had forgotten all about those curtains. They were OK when the bathroom walls were green, but when I got a bit older and painted the walls a primrose yellow (my mother let me paint the walls whatever colour I fancied), I got some pretty curtains from John Lewis with a wild flower design instead. And spent ages trying to scrape the transfers off the tiles. It never really happened. Those transfers last forever.
I wonder if anyone still has patterned towelling curtains in the bathroom?
Probably only grannies and grandpas who haven't change their bathroom decoration for 50 years, or supercool people from Hackney at the cutting edge of a trend no-one has yet caught up with.