Tuning stability and temperature

[ojkojbgoj]

To what extent does change in temperature affect tuning stability? On a practical level, how much does the temperature in the room have to change before a piano will drift noticeably out of tune?

[j_menz]

There's no straightforward answer to this. 

Changes in temperature do affect tuning, as do changes in humidity (and moving the piano and how hard you play it).  The bigger and/or more frequent the changes, the greater the impact.

Different pianos are affected to a greater or lesser extent depending on what they are made of (and some have special tricks to minimise the effects, such as Kawai and Yamaha for humidity).

[pianolive]

[quote Different pianos are affected to a greater or lesser extent depending on what they are made of (and some have special tricks to minimise the effects, such as Kawai and Yamaha for humidity).
[/quote]

What tricks could that possibly be?
I take care of many Yamaha and Kawai pianos and I find they are all very sensitive to changes in the RH.

[silverwoodpianos]

Agreed pianolive.

 I find here also that RH is more a factor in changes than average temperatures. I take care of many Kawai instruments and find them to be just as sensitive to changes as any other instrument.

Perhaps the other member was referring to the composite action parts which are supposed to resist this type of expansion/ contraction more than wooden parts.