How to adhere adhesive to glazed ceramic? I make decorative "flower" plates layering different shapes &amp; sizes to be hung on a wall or attached to a post in the garden, Each weighs approx 4- 5 lbs. 

I use either metal heavy duty picture hangars or PVC pipe elbow. I'm having trouble adhering both to the backs of glazed ceramic dishes.  I've tried E6000 clear glue, GE clear silicone for Windows &amp; doors, Fuze It &amp; PL500 landscaping construction adhesive. All cure for 48 hours and fail to stay on.

Any suggestions would be appreciated.
Google "structural epoxy for glass". I use structural epoxies weekly, and it's hard to find something they can't permanently adhere to. I'd give product recommendations, but I don't think it's allowed, and you'll want to find something local anyway.