Stuart Noble coughed up some electrons that declared:


The main feature of SBR is its small molecule size compared to pva, so
it mimics the behaviour of a solvent based product.

That explains a lot.

The slight downside
is that in a mortar mix the bulk of it tends to take off on its own into
the substrate, but that's beneficial in a screed .

Yes - I of course patched with an SBR 4:1 screed as it's only 15mm thick.

Difficult to get off your hands too, as I'm sure you've discovered by
now :-)

SS wire scourers work!

In fact scouring the float and trowels is the only way to clean the sodding
stuff off. I have a stainless metal bowl that I use for the cement/SBR
slurry and that has a layer of SBR+cement that won't come off with any
amount of scrubbing and banging - so it has provably excellent adhesion.

It *is* the new PVA for me

BTW - What is it like regarding adhesion to it by other things, say a few
weeks after it's dried?

It was slightly tacky for a week, but not any more. I was wondering to brush
on another thing layer the day before pouring the Stopgap...

Cheers

Tim