The fog filters through the in pipe, and then through all the ice, then into the plastic drier lint trap plastic thing "supercharger-carbonator", and then into the out pipe which the white plastic thing is mounted on. other than the fact that i usually concentrate the clc02 in that area, i always give the entire top of the ice the mixture. The only real purpose for the cap over the out pipe is that when using dry ice i put it there, but dry ice has not been necessary lol. The cap is to keep the dry ice protected from the water. just like dry ice foggers, your dry ice only lasts for like 15 minutes, but it'll sublimate over a span of 24 hours if it doesn't meet any water. The next few tests ill be doing will be setting the new lowest temps in both categories. Anyhow, if you just take ice and ice melt, you can get the same effect. Also aluminum is one of the best known thermocouples. don't use pvc! the fact that the pipes are in contact with water thats super chilled, but can't freeze, gains all the advantages over other designs. Think about it this way. Pick up an empty plastic pop bottle, and an empty aluminum can. Note to yourself which one seems to be colder, although they're both exactly the same temp. A full DIY episode is in the making.