Plastic parts crack in cold weather?

Okay, now we're talking about cracking do to dissimilar expansion
characteristics of 2 different materials. I this case you are correct, rapid
heating OR cooling could cause cracking. But just for wood, as I stated
earlier, moisture content of heat causes it to swell, while lack of moisture
causes it to crack.




"Michael Low" > wrote in message
oups.com...
> The walnut and redwood burl used in the E39 are very stable and very
> dense woods by nature. That's partially why they are good for
> inlaying. They would have been thoroughly dried before even being
> selected for inlaying. The pieces would have been finished with a
> varnish to protect the surface from dirt as well as moisture. It's
> true you can crack wood if it is green and you dry it quickly but it's
> unlikely to be the case with thoroughly dried dense burl hardwood
> that's properly finished.
>
> What we were referring to as heat is when you subject the wood to
> glaring sun. This can happen in the Summer or Winter but in the Winter
> the temperature differential between a very hot surface and the cold
> backing in contact with the car may be much greater. If there is a
> flaw in the grain of the wood, a severe heat differential may crack it
> right there because the wood is not that thick. One should always use
> a sunshade for the windshield.
>