So then I asked the guy how long until he does the stamp stuff. He told me about an hour. So I came back then and it still wasn't set up enough. It was nice and sunny today, but it was cold so that made it take longer for the concrete to set. I think I must have come back at least 3 times before he was actually doing the stamping, and then he was on the last little bit to do, so I got there just in time! It's a good thing it was finally hard enough or we would have had to round up some lights! They got done around 4:30 - which is getting pretty dark already - less than a month until the shortest day of the year!
So he had these round flat rubber-ish looking things that were textured on the bottom and he moved them around on the floor and pressed down on them with this square-on-a-stick thing.
After the seal goes on (and it's a bit lighter outside so I can see!) you will be able to see different colors in the concrete. There's the usual grey, but there's also a charcoal color and a hint of a green in there, too.