The icebox. That term brings thoughts of some cold winter day. Or a refrigerator stuffed with items that need to stay... Well, Cold. This term certainly does not explain the January weather we are having in Austin this week. Quite the opposite with temps in the upper 70s. It does, however, remind me that summer is coming and that this old 911 I am working on has terrible temperature control - and that it is made worse by the black paint. Think of it this way. Black is a light absorber. All the energy in the visible spectrum and beyond will be absorbed by black. And then this is radiated and transferred to the driver and passenger sitting under said roof.
Now, the nerd brain of mine decided I needed to change the heat transfer characteristics of the car. This is a wholistic approach. The first step is the interior panels.
Now, black surfaces absorb energy and release in different ways. White, on the other hand is a pretty good reflector of energy. We will not go into spectral analysis at this time. mostly because I do not have absorbance or reflectance spectra of my film coatings. what i can tell you is that without a doubt, specialty coatings work great.
In my last build (72 - Minne) I used this same coating stack and it makes a significant difference in how heat is handled in the car.
So, how about some science. Heat moves through materials due to phonons. A phonon is simplified as a vibrational wave in a material. Now, if you disturb how a material is put together it can help prevent phonons from from moving through. In my case, I used some ceramic nanospheres mixed in paint. These do 2 things; 1) prevent nicely organized layers of paint molecules and 2) because they are are hollow they do not let heat transfer through.
So, I mixed up some DIY thermal barrier paint and went to work. Once mixed, this is the consistency of peanut butter. But it rolls easily and goes on thick with a brush. 2 coats was enough to cover the interior. I coated floors, rear seat pans, rear deck, tunnel, roof underside and the inside of the doors.
Here are some pics.
Funny that the sun was out as I was painting. I got the first coat on the roof and noticed I was not sweating anymore. So yeah. It works.
There is more to the thermal management of the tub in a future update. Materials are in the works.