Thickness can matter a bit, but honestly, it's not as big a deal as technique and weather. I've worked with thicker TPO membranes and thinner ones, and once you find that sweet spot temp-wise, it's pretty consistent. As for scorching, you'll definitely know—you'll see brownish discoloration or the membrane surface getting shiny and brittle-looking. Trust me, I learned the hard way...better to practice on a scrap piece first than to explain a crispy roof patch to your spouse later.
"better to practice on a scrap piece first than to explain a crispy roof patch to your spouse later."
Haha, been there myself...nothing like the look you get when you come home smelling like burnt plastic. But seriously, temp-wise, I'd say start around 900°F and adjust from there. Keep your gun moving steadily—too slow and you'll scorch, too fast and it won't bond right. And don't trust the dial blindly; weather and wind can throw things off. Always test first, tweak as you go, and you'll find your rhythm.
I've found that around 850°F works better for me, personally. At 900°F, I noticed the TPO started to discolor slightly, especially on hotter days. Learned that lesson the hard way when I ended up with a patch that looked like burnt toast...not exactly subtle. Definitely agree about testing first though—conditions can vary so much day-to-day, it's always worth dialing it in carefully before committing to the real thing.
I've actually had decent results at around 900°F, provided I'm moving quickly enough and keeping a consistent pace. Discoloration can definitely be an issue if you're lingering too long in one spot or if the ambient temp is particularly high. But I wouldn't necessarily rule out higher temps completely—sometimes that extra heat can give you a cleaner weld, especially on colder mornings or when dealing with thicker membranes.
One thing I'd add though... humidity seems to make a surprising difference. I've had days where 850°F was perfect, but the very next day felt like I needed to bump things up slightly just because the air felt a bit damp. Definitely agree there's no one-size-fits-all setting here, and doing a quick test weld each day is probably the safest bet. Still, don't discount 900°F outright—just gotta keep an eye on your speed and conditions.
Interesting points, but isn't 900°F pushing it a bit? I've found that going too hot—even if you're quick—can sometimes make the membrane brittle over time. Maybe not immediately noticeable, but down the line it could affect durability. Have you checked weld strength after a few months at those higher temps? Curious if you've noticed any long-term differences compared to lower-temp welds...
