66 Remarhs upon Bleaching. 



Bleachers are generally sensible of the advanfages of heaf- 

 and various contrivances have been adopted to apply steam 

 heat to the purposes of bleaching. But I am not aware 

 that any one has attempted to bring his goods into action in 

 steam heat under pressure. Nor do I know that there has? 

 ever been any mechanical invention brought into practice, 

 by which it could be done, until my machine was construc- 

 ted. The French Bleachers have taken much pains to use 

 an alkaline solution at a temperature above boiling heat, but 

 without success. They seem to have a correct idea of the 

 probable effect of increments of heat above that degree, but 

 failed in their attempts to reach it, through the imperfection 

 of their mechanical inventions.* But I can find no evidence 

 of their ever having conceived an idea of the advantages 

 likely to result from the combined action oi heat and motion. 



Unless the steam is brought to act under pressure it is ev- 

 ident that no material benefit is gained by steaming instead 

 of boiling — often the reverse, because the heat will never 

 exceed, and the moment it is exposed to the atmospheric 

 air will fall below 21 2° Fahrenheit or boiling heat. But if 

 the steam is confined^ it is easy to raise its heat to 230'^ and 

 then the effect upon the linen shows, in the most unequivo- 

 cal manner, the advantages of augmented heat in bleaching. 

 This effect is not only more strikingly obvious, but is singu- 

 larly beautiful, when the goods are put in motion, and the 

 degree of bleaching is rendered perfectly uniform. 



There can be no danger, as some have apprehended, of in- 

 juring the linen by excessive steam heat,because the scorching- 

 heat of steam is 520° Fah. — a pressure of fifty atmospheres 

 or seven hundred and thirty five pounds upon a square inch 

 -—a pressure which no ordinary steam apparatus will resist. 



Steam heat at 350°. thermometical measurement, will so 

 far soften soldering as to cause it to yield to the pressure, 

 and the steam pipes will burst. These are facts which I 

 state as the result of my own repeated experiments, in which 

 I cannot be materially mistaken, and therefore I feel justified 

 in saying, that it is not possible with any ordinary working 

 apparatus, to carry steam to so high a temperature as to in- 

 jure any goods submitted to its action. By giving motion 

 to the linen, under the reciprocal action of steam heat, un- 

 der pressure, and alkaline liquor, the effect is not only more 

 powerful, than it can be by bucking, but, as already hinted, 



* Vide Berthollet on Dying. 



