Personally, I grow tiresome of the whole chemtrail/contrail debate. There are no chemtrails and if there were, you wouldn't see them, or they'd be
noticeable moreso than regular contrails. Contrails have been seen in the sky since planes have been able to fly at those altitudes.
What is a contrail?
Contrails (short for "condensation trails") or vapour trails are visible trails of condensed water vapour made by the exhaust of aircraft
engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets. If the air is cold enough,
this trail will comprise tiny ice crystals.
If you didn't understand it, read it again. A cloud of microscopic water droplets in the form of water vapor. When you stand outside on a very cold
day and breathe out, that is also condensed water vapor. If you were to walk backwards while breathing out, you would be creating a contrail. Your car
creates a contrail when you drive it around in the cold winter as well.
The water vapor down here on the ground evaporates. Water vapor high up in the atmosphere does not evaporate as easily and therefore hangs. That's
how we have clouds. Clouds are made up of the same exact thing, water vapor. In essence, aircraft engines are making clouds when they fly high enough
in the atmosphere.
Any chemical that is heavier than water would not hang in the air. Any chemical sprayed in the atmosphere would have to be an equal weight of water,
equal freezing-point as water and equal color as water. The only chemical that equals water is water. Any other chemical sprayed in the atmosphere
would have a different color, weight and freezing-point than water and would fall through the air instead of hang in the air like water.
As far as the "rainbow" effect, that's what water does in the sunlight. As far as the short contrail goes, when a plane skirts the part of the
atmosphere where it's cold enough to see the water vapor from the exhaust, then that is what happens. If you're driving around in winter and you
pull into a warm garage, the contrail from your car's exhaust also will go away. You pull back outside into the cold air, the contrail comes back.
The strong, upper-level winds will also distort and make different formations out of contrails (and clouds). You would feel these winds as turbulence
while riding a plane.
To sum things up, contrails are nothing more than water vapor from the exhaust of aircraft, just like the exhaust from your car or your breath in
winter. Any other chemical sprayed into the atmosphere that is not water would be very easy to tell that it's not water.