Water migration on fabrics

One of the easiest substances to image in the NIR spectral region is water. It is also an important substance to be able to monitor in industries concerned with absorbent materials, such as toilet tissue, paper towels, diapers, catamenial products and fabrics. The NIR images shown in Fig. 8.1 were collected with a 320 x 240 element InGaAs FPA through a 1.4 p,m optical bandpass filter. 

The four images shown in the top row of Fig. 8.1 were captured just as a drop of water from a pipette hit the fabric. All four fabric samples were from the same new fabric pretreated to provide stain resistance. Fabrics treated for stain resistance also tend to be water resistant. The fabric sample on the far left had never been washed. The second fabric from the left had been washed once in a detergent, the third 5 times and the fabric on the far right had been washed 10 times prior to the experiment. The four images shown in the second row of Fig. 8.1 were collected after the drop of water had been allowed to spread for 0.5 s (five frames later). 

It can be clearly seen that the successive detergent washings are affecting the surface energy of the fabric and allowing the water droplet to spread more quickly. 

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