Sparklers get super hot when you light them. Up to 2000 degrees by some measurements.
In this video, we see if the sparkling end of a Fourth of July sparkler is hot enough to ignite the gas inside a propane forge.
Disclaimer: I'm a professional blacksmith and retired firefighter. This video was created under controlled conditions with access to a fire extinguisher. This video is not meant to encourage risky behavior. It is solely for educational and entertainment purposes. Always use your best judgment.