Hi Andy,

> I resurrected a 10n one from the waste bin, connected the C meter (10.9nF at 
> Room Temp)  and turned a hair dryer on it.   C reduced to 5.4nF as I was 
> watching, and that was probably only around 50C.  
> Blowing on it shifted the value noticeably.

I have a batch of very bad (high temp coef) 22nF I sometimes use for undergrad 
teaching. Get the students to build an oscillator with them, watch the waveform 
and then grip the cap between thumb and forefinger. You can see the square wave 
width change visibly - you don't even need to measure it to realise it's 
happening.

73,
Chris G4OKW