Second ever melt – 1.669kg brass ingot, but why did it take so long?

Complete beginner here. My first attempt with copper was a disaster because I didn't preheat the graphite mould and the ingot got stuck.

Second attempt I switched to scrap brass and managed a 1.669kg ingot. It poured and released cleanly, so I'm pleased with the result, but the melt took far longer than I expected.

I'm using a small propane furnace and I'm still learning burner pressure and air choke adjustment.

Here's the full attempt if seeing the furnace/flame helps:

https://www.youtube.com/watch?v=RHjD68pU_mQ

Any advice on why the melt was so slow would be appreciated. I'm a complete novice, so feel free to point out anything obvious I've cocked up.