Surface pressure = surface tension of water minus the surface tension with a surfactant (measured). If the surface pressure changes, thus changing the measured surface tension. In Young's law with the wetting angle theta of the measured surface tension comes. Therefore,theta change during the film formation.

Best regards.

Thank you so much Mr. Mirgorod,

As we know in Langmuir-Blodgett trough we need the surface pressure diagram versus area per molecule, now do we need to measure the angle changes for this diagram? Is it important as the force changes?

Young's law is valid in the place of three-phase contact plate / gas / water. Determine the angle can only theoretically.

Regards.

Thank you for taking this into consideration.

Is the measurement accuracy of 0.1 mg enough for measuring the force?

I want to get a balance for my L-B trough.

Calculate yourself monolayer.

Yes