Polystyrene is a strong and stiff material, but also quite brittle. We have designed all of our polystyrene microplates (2- ,6,- 24-, and 96-well) in such a way that - if you put the MTP on a flat surface - there is always a 1 mm air gap under the bottom of the wells. We did this so that the ridges of the MTPs fit well in the groundplates of our clamp systems.

A consequence of this design is that - when centrifuged in a fully flat bucket - only the ridges of the wells are supported, and not the bottom of the wells itself. This may lead to "cracking" of the MTP.

Therefore, we strongly recommend to attach relatively hard rubber pads (122 x 80 mm, 2 or 3 mm thickness) in the center of the centrifugation buckets, and put the MTPs in the buckets in such a way, that the ridges fall around this rubber pad.

In this way the centrifugal forces exerted onto the cultures in the wells are directly "transferred" to the bucket (via the rubber), and "cracking" of the microtiter plates is much less likely to occur.