Heat lamp working properly

I just bought a brand new 100 watt heat bulb and dome fixture. I’m getting a Russian tortoise in a few months so I’m making sure the enclosure is gonna be perfect. I left the heat lamp on for about an hour and a half last night and it never got warmer than 80°. I have it sitting on the top of the cage and its about 12 inches from the bottom. Do they take longer to heat up or may I have a faulty bulb?

It might be too low wattage, I usually start with a 150-200 watt ceramic heat emitter.

Okay I’ll try that and see what happens. Thanks

You are going to need a stronger bulb.

Yea hopefully 150 watts works if not I’ll just keep going higher.