ers ed ▁ca . ▁one ▁mm ▁into ▁the ▁solution ▁and ▁then ▁slowly ▁with dra wn ▁from ▁the ▁interface . ▁The ▁main ▁forces ▁acting ▁on ▁a ▁pro be ▁are ▁the ▁bu oy ancy ▁( due ▁to ▁the ▁volume ▁of ▁liquid ▁disp la ced ▁by ▁the ▁pro be ) ▁and ▁the ▁mass ▁of ▁the ▁men is cus ▁ad her ing ▁to ▁the ▁pro be . ▁This ▁is ▁an ▁old , ▁reliable , ▁and ▁well - document ed ▁technique . ▁ ▁An ▁important ▁advantage ▁of ▁the ▁maximum ▁pull ▁force ▁technique ▁is ▁that ▁the ▁re ced ing ▁contact ▁angle ▁on ▁the ▁pro be ▁is ▁effectively ▁zero . ▁The ▁maximum ▁pull ▁force ▁is ▁obtained ▁when ▁the ▁bu oy ancy ▁force ▁reaches ▁its ▁minimum , ▁ ▁The ▁surface ▁t ension ▁measurement ▁used ▁in ▁the ▁P add ay ▁devices ▁based ▁on ▁the ▁du ▁No ü y ▁ring / maxim um ▁pull ▁force ▁method ▁is ▁explained ▁further ▁here : ▁ ▁The ▁force ▁acting ▁on ▁the ▁pro be ▁can ▁be ▁divided ▁into ▁two ▁components : ▁▁ ▁i ) ▁Bu oy ancy ▁stem ming ▁from ▁the ▁volume ▁disp la ced ▁by ▁the ▁pro be , ▁and ▁ ▁ii ) ▁the ▁mass ▁of ▁the ▁men is cus ▁of ▁the ▁liquid ▁ad her ing ▁to ▁the ▁pro be . ▁The ▁latter ▁is ▁in ▁equilibrium ▁with ▁the ▁surface ▁t ension ▁force , ▁i . e . ▁ ▁where ▁▁ ▁is ▁the ▁per imeter ▁of ▁the ▁pro be , ▁▁ ▁is ▁the ▁surface ▁t ension ▁and ▁the ▁weight ▁of ▁the ▁men is cus ▁under ▁the ▁pro be