home experiment - What’s wrong with my cloud chamber setup?

For my setup, I am using a fish tank, lined with black felt and with one side open for viewing and a slit on a side for the light. I have a pretty bright multi led flashlight. I am using dry ice blocks inside a stryofoam container that is separated from the chamber by a metal cooking sheet. I am using 91% IPA, and taped the bottom of the fish tank to the tray to seal it. I am using some hand warmers to heat the top of the tank.

All that happens (after 4 attempts) is that the IPA begins condensing onto the sheet. I never see mist. I have tried to reposition the light, and have used other lights. It is dark in the room.