That’s interesting about the 140°F mark—I’ve been using a temp gun too, mostly because I couldn’t trust my sense of touch after a few sunburns. I’ve noticed the same thing with bubbling and curling if the membrane gets too hot, especially on darker roofs. I tried misting with water once, but it just made things slippery and didn’t seem to cool much. For me, keeping the temp around 120-130°F has worked better, but I guess it depends a bit on the brand and color of TPO. It’s wild how much difference a few degrees can make.
I get where you’re coming from, but I’m not convinced 120-130°F is always the sweet spot. On some of the lighter TPOs I’ve worked with, especially in cooler climates, you actually need a bit more heat to get a proper weld. If the surface temp drops too much, I’ve seen seams fail early—just didn’t bond right.
I hear you on the misting, though. Tried that once and nearly wiped out... not worth it for the little difference it made. For me, it’s less about sticking to one temp and more about watching how the material reacts—if it starts to gloss up too fast or gets sticky, I back off. But yeah, darker membranes can go sideways real quick in the sun.
Honestly, I wish there was a universal number, but it always seems to come down to trial and error with each job.
Yeah, I’ve noticed the same thing with lighter TPO—sometimes you just need to crank the heat a bit more, especially if there’s any breeze. I usually go by feel too. If it starts bubbling or smells burnt, that’s my cue to back off. Never had much luck sticking to a single temp since every roll seems a little different.
I usually go by feel too. If it starts bubbling or smells burnt, that’s my cue to back off.
That bubbling thing got me the first time I tried it. I thought I was doing great until I noticed the edge curling up and this weird smell—pretty sure I cooked it. Ended up having to cut out a chunk and patch it, which was a pain. I’ve got a cheap heat gun with a dial, but honestly, the numbers don’t mean much. Every roll I’ve used seems to react different, especially when the sun’s beating down.
I’m in the Midwest, so wind is always a factor. One gust and suddenly the seam’s not melting right or it’s scorching. I’ve started doing quick test welds on scraps before I commit, just to see how it’s behaving that day. Not sure there’s a perfect answer, but I’d rather play it safe than risk frying a whole section again.
I get the whole “feel” thing, but honestly, relying just on bubbling or smell seems risky. TPO’s pretty sensitive—by the time you see or smell something off, damage is usually done. I’d rather use a temp probe or at least check with a roller test. Sun and wind really mess with consistency, but there’s gotta be a better way than just winging it every time.
