JET CHEMBOWS & The Science of Contrail Formation

When I was a child we did have jet aircraft. When I was a teenager, young adult and middleaged we also had jet airplanes. In school we were taught that rainbows in the sky were produced by the sun refracting off the moisture in the sky during or right after a rain. We were never taught that jets leaving contrails could create clouds OR create rainbows. We were never advised to look for rainbows in spreading jet contrails. Normal contrails did not spread back then. They may have lingered while the jet reached the opposite horizon. This happened on days of higher humidty.The rainbow in the photo above was caused by a jet that left the spreading emission.

Here is a definition of how a contrail forms from this website http://tinyurl.com/4pp8yh4. "Contrails form when HOT humid air from jet exhaust mixes with environmental air of low vapor pressure and low temperature." Ok.....this would explain the contrails I saw as a younger person that disappeared like  a wake behind a boat. The photo of what we call chemtrails, on the website above, shows far too many steaks in the sky for it to be normal air traffic out of one airport

Now.....think about when it's very cold outside and you breathe hot air out of your mouth into the surrounding air....or when hot exhaust exits from a car. It forms a cloud at first...right? But these short acting clouds disappear right away once the heated air, from your mouth or the car, cools off. Even if there are particulates from the car exhaust still in the air.....unless the heat remains with the particulates...there is no condensation cloud left for the eye to see.I believe it is the same principle with the jets. Can you imagine how lost we would all get in the clouds of condensation if all the air everyone breathed out on cold days remained for hours in the air AND expanded for a mile or so?

So...I still don't understand the mainstream explanation for contrails expanding and forming thick mucky cloud cover. As the jet exhaust cools, I would think that if it was a condensation trail that requires heat to form....that it would disappear once the heat source cooled off.As you can see our sky started out as bright deep blue this morning. It is now a pale silvery bluish grey from many jets leaving the feathery drifting emissions you see in the photo above.It has an almost metallic glint to it. Some have speculated that the jets have some kind of oil in the emissions and that this is what is causing the rainbow effects.. The emissions from the jets do seem to leave different types of trails and cloud cover depending on the humidity of the air.  No storms are predicited for today and tomorrow so the air might be drier and may account for the thin more wispy silvering of the sky as opposed to right before a storm when the contrails turn into thick cloud cover.The question is this......If contrails form behind a jet because of the heat emitted from the exhaust...then what causes contrails(chemtrails) to keep expanding after the heat source ceases?

Chemtrail activists say that this spreading and thickening of clouds may be due to chemicals , such as barium, which may be included in the jet exhaust emissions(fuel) or emissions from other contraptions which may be mounted on the jets. If I am explaining this incorrectly, please chime in