Had a similar experience working near some big skylights once—membrane heated up way faster than expected. Ended up dialing back nozzle temp and moving quicker to avoid scorching. Surface temp checks are definitely key, learned that lesson the hard way...
Yeah, skylights can really throw you off... I've found around 500-550°F nozzle temp usually works best, but if the membrane starts looking glossy or sticky, you're pushing it. Quick surface checks save a lot of headaches.
I've had mixed results around skylights myself. Usually, I hover closer to 500°F—550°F feels a bit risky to me, especially on older membranes. Had one job where the membrane started glossing up real quick at around 540°F, and before I knew it, it was sticky and nearly ruined. Learned my lesson there... now I always do quick test welds first. Saves a lot of stress later on.
Interesting you mention skylights—I had a similar scare around a chimney flashing. I was hovering around 530°F, thinking I was safe, and suddenly the membrane started getting that glossy look you described. Luckily caught it before it got too sticky, but it made me wonder if ambient temperature or direct sunlight plays a bigger role than we think. Maybe on hotter days or direct sun exposure, we should be dialing back the heat even more? I've heard some guys swear by welding early in the morning or late afternoon to avoid overheating issues. Curious if anyone's noticed a real difference welding at different times of day or under different weather conditions...
I've definitely noticed a difference depending on the time of day and direct sun. A few thoughts from my own DIY experience:
- Early mornings or late afternoons seem way more forgiving. Midday sun on a hot roof can easily bump your surface temps by an extra 20-30°F, even before you start welding.
- I've found myself dialing back my welder temp by about 20-30 degrees in direct sunlight just to avoid that glossy, overheated look.
- Cloudy days are actually ideal—steady temps, no sudden overheating surprises.
- Also, color matters. White TPO reflects heat, but darker membranes absorb it quick. So if you're working with darker materials or patches, be extra cautious.
Bottom line for me: ambient conditions and sun exposure are definitely bigger factors than I first thought. Now, I always test-weld a scrap piece first to gauge how the membrane reacts before jumping into critical areas like skylights or flashings...
