The problem of barrier leakage in surface pressure-surface area measur
ements has been overcome with a trough wherein the sample is compresse
d inside a band of teflon-covered spring steel strip. A computer-contr
olled stepping motor drive applies force to one side of the band, defo
rming it from a rounded triangle to a ''v'' shape. The compression ran
ge extends up to 4:1 and is repeatable to +/-2%. Calibration is conven
iently and accurately done with a computer-interfaced video imaging an
d analysis system. The design greatly simplifies the construction of s
urface troughs and completely obviates the possibility of leakage at h
igh surface pressures. The trough is useful for investigations involvi
ng high surface pressures and/or requiring long times.