The property responsible for this is available in the UIButton class:
myButton.showsTouchWhenHighlighted = NO;
You can access this (programmatically) in the UIBarButtonItem by assigning a UIButton element to the customView button customView and clicking the button. You can also do this in Interface Builder: drag a UIButton onto a UIToolbar and it will automatically add it to the UIBarButtonItem for you - then find the “Shows Touch On Highlight” checkbox under the button settings.
By the way, I don’t know how you customize your buttons, so feel free to ignore this, but if your button looks and behaves like a standard toolbar item, users expect a glow effect.
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