To break apart a glued joint such as the Duo-Art expression box try
putting it in the old deep freeze overnight before you try to break
it apart.  Just a thought.  An old-timer told me to do that with a
Gulbransen stack once.  I did not try it.

I use a heat gun and a little water to steam apart most old joints
or the handy dandy microwave or boiling water.

Don Teach