prepare distinct static packings of foam bubbles. By varying the
packing fraction we can approach the jamming transition as a function
of density, see the sequence of 4 experimental images at the right. By
advanced image analysis and rheometrical measurements we can then
extract various quantities that signal critical behaviour near the
jamming transition, such as the contact number Z and the shear and the bulk modulus. Our results show that a foam exhibits a jamming transition at a packing fraction f = 0.84, as shown in the lower plot, where the average contact number decreases to 4, the value at jamming, as Z-4 ~( f-0.84)1/2.