tuning the Hollow

When it comes to the tuning these Breath Instruments, there are many factors in determining wether its in tune or not. All my Breath Instruments are tuned at 22 degree Celsius with bottom end of instrument suspended in the air.

A player with an aggressive approach and tight cheeks and lips will tend to play slightly sharp, as where a player with a relaxed approach will tend to play slightly flat.

Then there is wether you play front on, or to the side. All instruments have been tuned playing front on style.

When tuning the instruments we have a room temperature of 22 degree Celsius, the instrument is played for about 15 min to warm the internal bore, then the final tuning is completed.

The air temperature inside the bore, rather than the instrument itself, is the critical factor here.
Because cold air is denser than warm air, the air molecules provide greater resistance to the sound vibrations and thus lower the pitch.
 
The pitch deviation of larger instruments is wider than that of smaller ones. Those with large bores and longer tubing take even longer to change temperature. 

We expect a pitch change of around 3 cents for each one degree Celsius change in temperature.
So for every degree minus 22 degree Celsius your instrument will be 3 cents flat, or for every degree above 22 degree Celsius your instrument will be 3 cents sharp.