Scientific American 36, 19.5.1855
We have received a letter from Robt. McCafferty, of Lancaster, Pa., in which he states that nitric acid destroys quercitron, and that the nitro muriatic spirits described in article No. 2, for dyeing yellow, are not the proper kind. The acids are entirely changed in their nature by tin. The best spirit for dyeing bark yellow on cotton, is the sulpho-muriate of tin, and this spirit as a mordant, is mentioned in the article to which he refers. He also objects to the expression, used in one of the articles: "some dyers use a great variety of spirits, but it is all nonsense." He says "no man can dye a purple with red spirits, for the aquafortis has a tendency to brown all colors; spirits of different proportions are used to dye different shades according to patterns." In one of the articles on dyeing, it is stated that the muriate of tin is the best universal kind of spirits to use. A skillful dyer can match different patterns by his dye stuffs and alternants (raisings,) independent of using a great variety of spirits. In the article describing purple, it is stated that many dyers use muriate of tin alone as a mordant. Some also use muriatic acid, saturated with the salts of tin. Different dyers employ different means to match the same patterns. He says he has to dye peach wood reds for 4 cts. per pound, and if he were to give 6 lbs. to the ten of cotton, it would cost him six cents per pound. In these articles, it is stated in a number of places that the exact amount of stuffs cannot be given, because there is such a difference in their quality. The object of each receipt is to produce a rich full color, and not to give the lowest priced shades. Here in New York Market are red colors on cloth differing in price five cents per yard. He also states the receipt for dyeing Royal Blue on page 160, is too dear; that it will cost $1,50 to dye 10 lbs. of cotton by it, whereas he can dye 10 lbs. for 25 cents, and use no logwood, but one pound of pearlash.
There is a great difference of opinion among dyers respecting the quality of colors. If he can dye a good dark royal blue for 25 cents per 10 lbs., using 1 lb. of pearlash, he certainly is in possession of a grand secret, for pearlash at wholesale is over $6 per barrel. He must therefore use but a few ounces of tin and prussiate. Smith, in his "Dyer's Instructor," a recent London work, gives 1½ lbs. of the prussiate of potash and 1 lb. of the crystals of tin to 10 lbs. of cotton, or half a pound more prussiate than in the receipt on page 170.
In raising prussian blues (deepening and blooming the shade) silk dyers have been accustomed to use urine and salammoniac, in milk-warm water, after the goods were dyed in the prussiate. It is an old plan with dyers of prussian blues to run the goods through a potash lye, after dipping in the iron.
Mr. McCafferty did not intend his letter for publication; but we have given the substance of it, because of its straightforwardness. He cannot but admit that all the receipts given will dye the specific colors, and good colors too; this is their principal object.
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