Is it normal for the surface to look this dull before they start stamping the pattern?

That wet sheen disappearing is actualy your best indicator that the bleed water has evaporated and it’s almost time to get the mats down. You ussually have a window of about 30 to 90 minutes depending on the slump of the mix and the ambient temp, but high humidity actually buys you a little extra time compared to a dry, windy day. If he’s grabbing the **powdered release** now, he’s likely right on schedule. You want the concrete to be plastic enugh to take an impression but firm enough to support the weight of the stamps and the person walking on them without sinking in more than a fraction of an inch.

The biggest risk in these conditions isn't necessarily it setting too fast across the board, but the surface "crusting" while the bottom stays soft. If he waits too long, you’ll see the stamps start to tear the surface rather than pressing into it, which creates those messy edges you’re worried about. A good way to check is the thumb test: press your thumb into the surface. If it leaves a clean indentation about a quarter-inch deep without sticking to your skin, it's prime time. If it’s still mushy, the stamps will slide; if it’s rock hard, he’s going to be fighting it with a tamper for hours. It's good to see he’s got a crew moving on it. Some of the best finishers I know started out as kids helping thier dads or uncles on site, and that kind of village mentality is how you get a quality job done before the mud gets away from you. Having an extra set of hands to move mats and broadcast the release while the lead finisher focuses on the **stamp alignment** makes a massive difference in the final look.

Keep an eye on how the mats are seating. If you see him having to jump on the tamper with all his weight just to get a faint line, the window is closing fast. But if the mats are going down smooth and the release is keeping everthing from sticking, you're in good shape. Just let them work their rhythm; stamping is a high-stress hour where every second counts.

Don't sweat it too much. When that sheen's gone, it's go time. I've seen jobs go south 'cause someone waited for it to get too firm, especally near the edges where the forms soak up moisture. If he’s hitting the perimeter first, he’s likely on top of it. Just make sure he’s not leaving big gaps between the mats as he moves. Once it starts kicking, it doesn't wait for nobody. You’ll know pretty quick if he’s struggling to get the depth you want.

I realy don't know much about this yet, but does that powdered release agent they use affect how fast the surface dries out? Also, if they realize it's getting too stiff to take a good impression, is there any way to 'reset' the surface or soften it back up, or is it basicly game over once it starts hardening? I've seen some finished patios where the stamp lines look a bit crumbly or frayed, and I'm wondering if that's a sign it was alredy too dry when they started. It's wild how much of a race this seems to be!

Spot on about the timing. If he's grabbing the release now, he's definitely in the zone. One tiny detail people forget is the 'floppy' mats. If he’s got a set of those thin, flexible stamps for the edges near the house or the forms, you’re in great hands.

Rigid mats are great for the bulk of the pour, but they can't get tight against a wall once the concrete starts to resist. If he’s just muscling the big mats into the corners, the pattern usually ends up shallow there. Seeing a few floppies on his stack is a tell-tale sign of a pro who knows how to handle the perimeter details.

Update: You were right about the sheen; as soon as it dulled, he started stamping. Those floppy mats realy helped get the pattern tight against the house. I'm still dealing with some unevenness where the heavy mats met the edges, though. Is there any way to touch those up tomorrow once it’s harder, or am I stuck with it?