I asked about a silicone for sealing between a step and the brickwork to
which it's faced.

Steve Firth replied thus

is there a reliable silicone for this job? It seems to me that when

No.

silicone first appeared in tubes, it was magnificent stuff. In recent
years there seem to be dozens of different brands and types of
"silicone", some of which to my certain knowledge dissolves in water.

I suspect that you will find that the silicone that dissolves on water
isn't silicone. It will be a sealant but is likely to be acrylic, not
silicone.

For the use that you intend, I would use polysulphide sealant, not
silicone. A good alternative is polyurethane sealant such as Sikaflex.

Thanks Steve (the only reply! I always feel embarrassed when there are
very few replies: seems to imply I asked a dumb question!).
I've now got some polysulphide sealant: Evostick: *bloody* expensive,
but I'm sure this is what I need. The sealant shelves in the builders'
merchants are pretty intimidating these days!

John