Burn marks around incandescent fixtures

[Edwin]

I was at Reptilia a few days ago, and I noticed that several of their tanks had burn marks around their incandescent light fixtures, particularly in the burm and retic tanks. I am now concerned that it might happen to my terrarium, as I have a similar setup. Is there any way of preventing this from happening?

I am using a ceramic light fixture that can hold up to 660w, connected to a pancake box. It has a 150w CHE on it.

Would purchasing an analog thermostat help?

Thanks in advance,
E