BLUEING 163 



yellowing of straw hats during the summer is familiar to every 

 one ; the straw is merely resuming its natural color which had 

 been modified by the sulphurous acid applied to the straw 

 when woven. 



Why the color returns. Some of the compounds formed 

 by the sulphurous acid bleaching process are gradually decom- 

 posed by sunlight. In consequence the original color is 

 slowly restored. The portion of a hat protected by the band 

 retains its fresh appearance because the light does not reach 

 it. Silks and other fabrics bleached with sulphurous acid 

 fade with age, and assume an unnatural color. One reason 

 for this is that the dye used to color the fabric requires 

 a clear white background, and loses its characteristic hues 

 when its foundation is yellow instead of white. Then, too, 

 dyestuffs are themselves more or less affected by light, and fade 

 slowly under a strong illumination. 



Materials which are not exposed to an intense and pro- 

 longed illumination retain their whiteness for a long time, 

 and hence dress materials and hats which have been bleached 

 with sulphurous acid should be protected from the sun's glare 

 when not in use. 



The removal of stains. Bleaching powder is very useful 

 in the removal of stains from white fabrics. Ink spots rubbed 

 with lemon juice and dipped in bleaching solution fade away 

 and leave on the cloth no trace of discoloration. Sometimes 

 these stains can be removed by soaking in milk, and where this 

 is possible, it is the better method. 



Bleaching solution, however, while valuable in the removal 

 of some stains, is unable to remove paint stains, because paints 

 owe their color to mineral matter, and on this chlorine is power- 

 less to act. 



Blueing. No matter how carefully material is bleached 

 in the mills, and how white it is when purchased, it slowlv 



CLARK INTRO. TO SC. XX 



