"This is the most difficult feature of the whole handicraft, the actual coloring, and yet for fine effects I should recommend only the use of hand-dyed materials. Goods dyed by professional dyers are perfectly uniform in color throughout, and rugs made of such material will have nothing of that difference of tone, that play of color, that is absolutely necessary for beauty.
"In dyeing use only brass, copper, granite, or porcelain kettles, unless one goes into it on a large scale and uses regular machinery. Brass and copper vessels are to be preferred, while iron, or tin showing iron, are to be carefully avoided, as the mordants have a great affinity for iron and ruin the color. I use a large brass kettle holding about five gallons.
"For mordants I use Glauber salts and sulphuric acid, and with the weight of cloth I use, it takes 3 oz. of Glauber salts and 3/4 oz. of sulphuric acid (full strength) to each six yards of flannel. I use a one-ounce Phenix graduate (American standard) measuring glass, and as full strength sulphuric acid has about twice the specific gravity of water, one should measure by the scale engraved on the right-hand side of the glass. The left-hand scale is based upon the standard unit of weight, which is water.
"In using sulphuric acid I dilute it in a little cold water in a cup by pouring the acid on to the water, as sulphuric acid in uniting with water causes a chemical reaction. Where a large quantity of acid is used this reaction is accompanied by a sudden burst of steam, if the water falls upon the acid. But in a small quantity as this, there is no possible danger of accident if the acid is poured on the water. Sulphuric acid should be closely stoppered and used with care, as it is corrosive, eating holes in cotton or linen fabrics. With ordinary precautions it can be used without the least difficulty.
"Glauber salts are too well known in commerce to need description, and are used to neutralize the acid. The two in combination do not injure woolen fabrics, but merely set the dyes.
"In preparing the dye bath allow three gallons of water, and 3/4 oz. of sulphuric acid; stir thoroughly and add 3 oz. Glauber salts to six yards of cloth. Then add the dyestuff in required proportions. Stir thoroughly as each ingredient is added, for the evenness of the dye depends upon the thorough distribution of the mordants and color in the dye bath. Generally it is advised to strain the dye before it is added, but, as an even tone is not the desired result for this special handicraft, I never follow this suggestion.