The diffusion of water vapour from the human body involves passage through
a confined air layer between skin and fabric, through the textile itself, a
cid across an outer boundary layer, Measuring the vapour flow resistance of
the textile also needs a precise determination of the two air layer resist
ances, which is difficult to achieve, These three resistances are first vis
ualized on a holographic bench, and then the mass flow is obtained with hig
h accuracy using a micro-weighing technique: the evaporation rate is measur
ed as a function of time for configurations of one and two fabric layers wh
ich seal a calibrated drum of evaporating liquid. Using benzene instead of
water gives heavier vapours and a greater and more easily measured evaporat
ion rate. The results can be easily converted to their equivalent air thick
ness for water vapour, The agreement between theory and measurement leads t
o useful insight into the relative importance of the fabric resistance comp
ared with that of the two adjoining air layers, The technique described her
e is not applicable to all types of textile, especially less porous structu
res.