Wool Material Shrinking from Heat

[lone ranger]

I have a hat, made from what I believe is rabbit hair (not leather, just the hair). I sometimes leave it in the car. I have noticed that if I leave it in the car for a long period, when it is hot, the hat shrinks.

I have 2 questions.
A. Why does this shrinking happen?
B. Is there any way to prevent this? One idea was perhaps introducing humidity into the car or container that hold it. Any other ideas?

Thanks

 

[chemisttree]

Place the car at a more northerly latitude. It is likely that dessication is the culprit. Old fashioned hydrometers used horse hair and it's change in length vs. relative humidity as the active component.

Here's http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=142598"

 

[lone ranger]

Thanks for reply. I don't think it is that simple. If it is just humidity, then when brought back into regular weather, it would expand, which it doesnt.