vibration and resonance

I need to get rid of vibration and resonance in my homemade rack that is to "lively and rings like a bell". I was told to try DYNAMAT on the underside of the shelves. Would cork be the same or better? What is your experience? Thanks
Do you have the rubber washers between the nuts & the shelves like the salamander racks do?
I built a rack from slate and threaded rods. My rack is very heavy but will wobble if the nuts aren't tight. I really crank them to make it rigid.