t54 Ohfervat'wns «n Madderlrig, 



For dveing my red, I employed three parts of the beft 

 madder for one part in weight of dry cotton thread. 



With the precaution I took to obtain an uniform (hade I 

 could have dyed at one time, but I Ihould always recom- 

 mend peifoni ing this operation at two dificrent times, taking 

 each time half a portion of madder and of chalk, if the (kains 

 cannot be continually turned in ihe boiler: it may fcrve alfo 

 for clearing, by adapting to it a cover fo as to luffer very little 

 of the vapours to efcape, becaufc it would be too expenfive to 

 replace the part evaporated by more boiling water. By ope- 

 rating on a large fcale, and concentrating the heat in the 

 boilers, keeping them ahnoll clofc, there, perhaps, would be 

 no need of emploving eight hours ebullition to clear and fix 

 the colours. I have every reafon to believe that this clearing 

 of the Turkey red gave rife to the idea of bleaching with 

 fteam : it muil have been feen that colours by being cleared 

 lofe confiderably in regard to their intenfuy ; and perhaps it 

 has been obferved at the fame time that the packthreads em- 

 ployed for arranging the fkains were bleached during the 

 clearing, efpecialTy when alkalies were added. 



A great variety of colours and of different Hiades may be 

 obtained by tollowing jhe procefs here defcribed for obtain-r 

 ing beautiful and durable reds. In this cafe, the oily alkaline 

 folution of alumine mufl not be employed till the required 

 fliade cf oxide of iron or indigo blue has been given ; but 

 whatever may be the colour or (hade wliich you wifh to give, 

 before you fix the alumine on the fkains of cotton or linen, 

 thefelkains mu(} always be firft well boiled, by which means 

 the adhefion of the indigo fecula as well as that of the oxide of 

 iron will be increased in the fame manner as that of alumine 

 coloured by the colouring parts of madder when fubjciSled to 

 ttie action of the heat of boiling water before they are im- 

 pregnated with the oily alkaline folution of alumine. As the 

 niethod of dyeing mdigo blue in all its Ih^des is well known, 

 it is needlel- to detail it ; and as to ^ivinix a rufty yellow colour, 

 which may be done at little expenfe, nothing is necefTary but 

 to moiften the fl^aius well with a folution of the fiilphate of 

 iron, to prcfs lliem equally, and then to inimerfe them in a 

 cauftic ley of potafl;, which will precipitate and fix the oxide 

 of iron of a difagreeable colour, but which will not fail to 

 all'ume a rufty yellow fnade by attracfting and becoming falu- 

 raied with the oxygen of the atmofphere : thus yellow will be 

 more or lefs dark according to the quantity of the lid|)hate of 

 ir(jn in folution. More intentitv and even more equality 

 may be given to the ruily yellow by moillcning the fkains a 



fecond 



4 



