Witnessing such dark spots easily disappear with the use of hydrosulfite, one suspects that an azoic type colorant might have caused them.

But then in the drying stage after rinsing, the spots reappear, to one's surprise. It is often not a case of mould. Mould is rarely detected even through an electron microscope. The stain is caused by colorants that take effect by oxidation, i.e., oxidation dyes, in most cases.

Today, the most readily-available oxidation dyes are the ones used for hair, not the so-called 'temporary' or 'semi-permanent' types, but the 'permanent' hair dyes containing para-phenylenediamine or para-tolylenediamine. They are bleached out by reduction, however, colors return through oxidation in rinsing and in drying. Thus it may be concluded that it is hair dye that accidentally spilled over and has taken effect by oxidation. Such stains, because of the extremely high dyeing fastness, will probably never be removed unless by the use of chlorine-based bleach that will also damage the fabric.

With an increasingly aging population, hair dyes will be used more and more here in Japan where grayness rather stands out in contrast to our generally black hair.

Naturally, spilling and staining accidents will more frequently be caused. Careful assessment will be of significance.

(T.T.)