Well.It seems that Nyton can load 135g!This is the effective load that make the baloon reach the equilibrium(almost).
This test is done with a box that weights 98g(screws included) and some nails that weights about 4,6g each.
I needed 8 nails + the box that is about 135g of load.
It means that the lifting force is equal to 0.135*g so about 1.3Netwon