ManiifuLlure of Hats, 403 



In faft, when the fulphuric acid is employed, it is ufelefs to keep the bath nearly boiling, 

 as was formerly done. A degree of heat of twenty-five or thirty degrees (90° or 100" 

 of Fahrenheit) is fufficient for good fulling. The faving of fuel is an objedt of importance 

 in manufaftories ; and as very little fire is necefTary when fulphuric acid is ufed, cauldrons 

 of lead may be fubftituted infteaU of copper boilers, the firft coft and annual repair of which 

 are very confiderable. 



The felts prepared by the new procefs are alfo of a very fuperior quality to thofe which 

 have been worked in the bath with wine-lees. In fact, the mucilaginous and colouring 

 matters of the lees, which are fufpended in the bath, penetrate the texture of the (lutf, and 

 adhere with more or lefs fqrce ; and when after having pafled the hats through the dye they 

 are beaten, a fine black dud flies oif in great abundance, which not only weakens the texture 

 of the felt, but by dilFufing itfelf through the manufa(n;ory greatly incommodes the workmen, 

 and frequently occafions coughs and diforders of the throat. 



The manufafturer, accordingly, who made this firft trial, continues to employ it in pre- 

 ference to the old procefs } and, according to his report, the advantages are incalculable : 

 " Hats felted in this manner," fays he, in one of his letters, " are not only clear of the 

 powder which abounds in the others, but they take the dye better. Us s'ejarrent mieux, and 

 are cleaner. The workman has not his bath fo hot, which is to him a convenience no 

 lefs valuable than the faving of fuel to the mafter. 



Befides thefe advantages, the wine-lees formerly made ufe of by the hatters in large quan- 

 tities will remain for other ufes, in the fabrication of faltpetre, foft foaps, and for other de- 

 firable purpofes *. 



When I had afcertained that the fulling of hats was principally determined by the por- 

 tion of acid which exifts in the lees, I determined to fubflitute the oil of vitriol, or fulphuric 

 acid, becaufe it is found in the market at a reafonable rate. But though all the acids have 

 common properties in which they refemble each other, they have alfo others by which each 

 is peculiarly diftinguiflted. It would therefore be of importance to examine, among the 

 numerous clafs of acids, whether fome one might not have a more dlreft aflion upon the 

 fluff than any of the others, fo as to fhorten the labour, without prejudice to the article or 

 the economy of its preparation. Could not acid liquors be prepared in the manufaflory itfelf, 

 by fermenting barley, or bran, or fome fuch material ? This is an object of refearch, to which 

 we may invite manufaflurers, and others who are attached to the cultivation of the arts. 



I fliall not here defcribe the procefles of dyeing. In the manufadlory of La Cote d'Or, the 

 nut-gall is not ufed ; and oak-bark has been fubftituted with advantage : but thefe methods 

 are known, and have been already publifhed. I proceed to the fourth and laft operation of 

 hat-making. 



It confifts in lining the inner furface of the crown, as well as of the brim of the hat, with 

 a glutinous fubftance, which in drying gives firmnefs to the work, and preferves its form. 

 The ufual compofition is made of gum arable, common gum, and Flanders glue, which are 



» The Ailphurk acid, more or lefs diluted with wnter, might be advantagcoudy uTtd in many of the arts. 

 Thus the braticrt ufually employ Ices to clean and brighten tlicir work ; ami moll ccrtiiinly they would obtain 

 the fame effcft by fimply dipping the piece in water (lightly acidulated with fulphuric acid, which would alfo 

 fare tlitm the trouble of rubbing the work for a long time, as they are obliged to do when they ufe Ices, &c. C. 



3F2 diflblvci 



