TEXTILES 235 



this field (Remuth, 1947). Phase microscopy was reported for observing 

 bacterial and enzymatic decomposition of wool, fine detail in 1- to S-ju 

 cross sections of wool, bacteria and f\mgi on unstained fibers, fine 

 structure in thin sections, inclusions, turbid portions and samples with 

 small density differences, thickening pastes and their penetration, 

 liquid crystals in liquid soaps and lubricants, solid crystals and thin 

 plates, particles embedded in fibers such as silicates, and fissures in 

 fibers due to laundering. Objections to the method included failure 

 with thick objects, failure with large differences in index such as between 

 a fiber and a delusterizing agent, and failure with pigments and with 

 oblique light. Modern eciuipment with long working distance con- 

 densers and phase objectives with various kinds and types of diffraction 

 plates have met many of these objections. 



Royer and Maresh (1947, 1949) also summarized many of the applica- 

 tions of phase microscopy in this field through a discussion of thickness 

 variations, rayon cross sections, pigments, emulsions and dispersions, 

 and thin coatings on textiles, paper fibers, leather, and pigments. 



The scales on wool show well without stain with a medium A — dark- 

 contrast phase objective. Lanaset coating on the wool scales may be 

 seen with a 0.07A+0.25X diffraction plate (Calco, 1947; Royer and 

 Maresh, 1947). Hairs may be studied when not too pigmented; the 

 medium dark-contrast A— and high bright-contrast A+ plates have 

 usually been found preferable for the lighter ones and the 5B— 0.25X for 

 darker pigmented hairs (Chase, 1949). Pigmented hairs are usually 

 examined with the aid of a replica of their surface, and the phase micro- 

 scope will improve the visibility of details seen in the replicas. For a 

 nigrosine method like that of Koonz and Strandine (1945) the IB — 0.25X 

 plate would be preferable, and for transparent replicas such as described 

 by Hardy and PHtt (1940) either bright- or dark-contrast low or 

 medium (0.14-0.2A±0.25X) phase objectives would be useful. 



Farr (1946, 1949) has shown the value of the phase microscope in 

 determining the structure of cotton fiber and related materials. These 

 fibers may be examined as found and then during or after treatment with 

 solvents such as cuprammonium, or with macerating agents. Bright 

 contrast offers some advantage in the study of fibers. For single fibers 

 the phase microscope is useful in assessing maturity, but for masses of 

 fibers the conventional staining technics are better. 



"Dopes" may be examined for gel inclusions and for undissolved 

 fibers. The 0.07A+0.25X plate is better for the former and the 

 0.14A-0.25X and 1-2. 5B -0.25X plates for the latter, depending on their 

 size. Rayon yarn fibers and their cross sections (Fig. VI. 7) may be 

 examined when mounted in paraflfin oil. The extent of the skin shows, 

 and when mineral or oil globules have been added for delusterification 



