My cheap IR thermometer said 170°F before I even plugged in the heat gun, which seemed wild.
That’s honestly not surprising—TPO can get crazy hot in direct sun, especially if you’re on a white roof. Waiting until after dinner was a smart move. I’ve seen more seams ruined by mid-day welding than I can count. You’re dead-on about trusting your senses over gadgets sometimes... those temp strips are basically useless once the sun’s involved. If it’s bubbling, it’s definitely too hot, but you figured it out before things got ugly. It’s all about timing and patience with this stuff.
those temp strips are basically useless once the sun’s involved
That’s spot on. Direct sunlight throws off most handheld readings, especially with reflective TPO. I’ve seen IR thermometers give numbers all over the place—sometimes 30°F off from actual weld temps. Trusting your hands and watching for bubbling or gloss changes is usually more reliable. Timing your work for cooler parts of the day really does make a difference; I’ve had crews try to push through mid-afternoon and end up with failed seams later. You avoided a headache by waiting it out.
Yeah, I’ve run into the same thing—those temp strips are more of a suggestion than anything once the sun’s beating down. I remember one July job where we tried to rely on them and ended up chasing our tails. The TPO was so hot from the sun that even with the gun dialed way down, we still got scorched seams. Ended up having to redo a whole section after it cooled off. Now I just go by feel and look for that slight gloss shift, like you said. Midday welding is just asking for trouble, especially on white roofs. Sometimes it’s better to grab some shade and wait it out... saves a lot of rework later.
That brings back memories of my own summer project a few years ago. I thought I was being clever, starting early, but by 10am the roof was already radiating heat like an oven. I tried using those temp strips too, but they were all over the place—sometimes reading way higher than what felt right. Ended up trusting my gut and watching for that subtle sheen change, just like you mentioned. Honestly, waiting out the hottest part of the day saved me a ton of headaches. It’s tempting to push through, but I learned the hard way that patience pays off with TPO.
Yeah, those temp strips can be all over the map, especially once the sun’s really beating down. I’ve found that sometimes just waiting for late afternoon makes a world of difference—less stress, fewer mistakes. Trusting your gut and watching the material is underrated, honestly.
