R20 Surface Retarder
I used this on 28 July 2023 - and just after I had applied it, a shower came through and added considerable moisture content to the surface. I tried covering with plastic, but by the time I got the plastic out and on, it had rained quite a bit. So, I think the retarder's effect was reduced/diluted. While the product info suggests a 12 - 24 hour delay prior to exposing, my project was ready for washing in 8 hours, despite it being cloudy and cool (15-20 degrees). Exposing turned out quite well, but there is a lot of efflorescence. I'm hoping that will be erased with the Efflorescence Dissolver.