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.
