That's a solid tip, I've seen experienced roofers do something similar. Another thing I've noticed is they often test on scrap pieces first to dial in the heat settings before hitting the actual seams. Ever tried practicing on scraps beforehand?
Testing on scraps is definitely the way to go, especially if you're not welding TPO every day. I've seen guys skip that step thinking they know their gear inside-out, only to end up scorching the membrane or getting weak seams. It's a small step that saves a ton of headaches later.
As for how hot is too hot... honestly, there's no magic number because it depends on your gun, nozzle size, ambient temperature, and even how fast you move. But generally speaking, if you're seeing smoke or discoloration, you're pushing it too far. The sweet spot usually means the membrane welds smoothly without resistance or bubbling. If it's dragging or sticking badly, that's usually a sign you're running too cool.
One trick I've picked up over the years: keep an eye on your roller marks. If they're clean and consistent without wrinkles or burn marks, you're probably dialed in just right.
Good tips here, especially about checking roller marks. A lot of guys underestimate how much those little details matter. One thing I'd add is that ambient temps can really throw you off—had a job last summer where the same settings I always use suddenly scorched the membrane because it was baking hot outside. Definitely pays to slow down and double-check your welds when conditions change... learned that one the hard way.
Good point about ambient temps, but honestly, I think the bigger issue is surface temperature rather than just air temp. I've had days that didn't feel crazy hot, but the membrane itself was roasting from direct sun exposure. If you're welding midday, it's worth checking the actual surface temp with an infrared thermometer. Sometimes shading your work area or shifting your schedule earlier in the morning can save a lot of headaches... learned that after a few frustrating afternoons myself.
Totally agree about the surface temp thing. Last summer I was welding TPO after a storm, and the air felt pretty comfy, maybe upper 70s. But man, the membrane was sizzling hot to touch—felt like flipping burgers on a grill or something. Ended up rigging a tarp shade and it made a huge difference. Now I always keep one of those infrared thermometers handy. Saved me from some real headaches since then...
