It has previously been shown that capillary measurements may be interp
reted in favor of hydrophobic slippage. Here, the possible implication
s of this phenomenon for using the drainage technique for hydrophobic
attractive force measurements are studied numerically. Attention is fo
cused on investigating the role of various experimental conditions in
the surface force apparatus. We demonstrate that under experimental co
nditions discernible deviations from the Reynolds theory may occur due
to slippage. The misuse of Reynolds theory may lead to overestimation
of the hydrophobic attractive force. We conclude that the apparent ex
tra attraction has to depend on both the parameters of the surface for
ce apparatus (configuration geometry, stiffness of the spring, and dri
ving speed) and the types of surface interactions in the system. Appar
ently the only possibility of distinguishing between deviations from D
LVO theory and deviations from Reynolds theory is to perform the drain
age rate measurements at various driving speeds. However, sometimes th
e effect of slippage will be undistinguishable from that of the hydrop
hobic force, because the apparent hydrophobic force will be nearly ind
ependent of the driving speed.