I do not believe that any decided decomposition of the alum takes place without the 

 intervention of the cloth; and perhaps too, not without the further intervention of 

 colouring matter. But these facts have not yet been chemically ascertained; and every 

 chemist knows the obscurity that yet hangs about the operation of common tartar in 

 the silvering of brass and copper, and the tinning of brass wire for pins. 



2. Mordant for woollens. To a pound of aqua fortis, add a pound of pure clean rain 

 water, and two ounces of sal ammoniac. In this mixture, slowly dissolve two ounces of 

 grain tin, then add one ounce of powdered white tartar. When you dye with the woods 

 or plants, first let the cloth stay for fifteen minutes in this solution diluted, using it in 

 the proportion of one-fifth or one-sixth part the weight of the cloth. Then having soaked 

 it in this solution and dried it moderately, enter it into a hot decoction of the plant, 

 and when it has taken up as full a colour as it will, take it out of the decoction, rinse 

 it well in cold water, soak it again in the mordant and dye it again. Then wash it well 

 and dry it, as a specimen of the colour with the tin mordant. 



3. From some experiments I have made, I believe the tin mordant may be as usefully 

 prepared in the following as in any other way, but it is not the actual dyer's practice; 

 which the preceding method approaches as far as may be: except that I have directed 

 the usual dose of tartar to be put to the mordant instead of putting it to the dye stuff, 

 as in the scarlet dye. 



Make an aqua regia thus. Muriatic acid, from iron, three parts; nitric acid, one part. 

 Dissolve slowly as much tin as it will take up, pour it off clear, and then add muriatic 

 acid in like proportion to the amount of one -sixth in quantity of the solution, so that 

 there shall be an excess of acid. Of this, when diluted with an equal quantity of water, 

 employ one part by weight to six or eight parts of cloth. 



But the second process being the process of practice, I should upon the whole prefer it. 

 We sadly want a judicious set of experiments on mordants. Indeed no man but a dyer 

 by practice and a good chemist into the bargain, can even guess at the multitude of 

 desiderata in the art of dyeing; and how little we know about it as yet. 



These, with iron and copper, will be mordants enough for woollen. The pieces of 

 flannel used for these experiments should be not more than six inches square, cut off 

 after the cloth has been mordanted with alum and tartar, but divided before the tin 

 mordant is used. The weight of each piece may be ascertained by weighing the whole 

 piece first. 



4. Dissolve four ounces of green copperas in a pint of water, and add two ounces of 

 finely powdered tartar. Stir them till dissolved; this will be the utmost proportion for one 

 pound of cloth. 



Mordant the cloth with this in all proportions, (noting them) and mix it also occasion- 

 ally with the alum and tartar mordant, wherever you want saddened colours, as is done in 

 practice for olives and drabs. 



5. Make a similar mordant, using blue instead of green copperas. 

 Secondly. Mordants for Cotton. 



1. Take a given weight of callicoe well bleached. Immerse it for six hours in water 

 acidulated with sulphuric acid; to wit, one part oil of vitriol to fifty parts water. Take it 

 out, wash it perfectly and scrupulously. This is necessary to dissolve any alkaline or earthy 

 mordant which the cloth in bleaching is apt to imbibe. The callicoe printer never 

 dispenses with this. 



2. Make a mordant merely of alum: using four ounces of alum to one pound of callicoe, 

 and soak your callicoe in this mordant boiling hot, for six hours. Keep it in a damp place. 



3. Make a mordant of acetat of alum, as in common practice, though it be not perfect: 

 but for these experiments common practice is the best foundation to build upon: thus, 



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