2. Repeat the same experiment and use a piece of cotton cloth that has been previously washed in common alum.[25] Note the effect. Which has the greater attraction for dyestuffs, cotton or wool? Why is alum used?
3. Repeat the same experiment, using first the same weight of cotton yarn and then the same weight of cotton sliver. Notice the results.
Which piece of cotton holds the dye best, that which was dipped in alum or the one that was simply boiled in the solution?
Experiment 22—Weighting Silk.—Affinity of Metallic Salts for Silk
Apparatus: Porcelain dishes.
Material: Silk yarn.
Reference: Textiles, pages [212-214].
Directions
1. Weigh separately two skeins of dry silk and distinguish skein No. 1 by looping some cotton thread into it. Prepare a tepid bath containing 10 gm. strong sumach extract in 400 cc. water. Enter the skeins of silk and work for 15 to 20 minutes, meanwhile slowly raising the temperature to about 150° F. Remove, squeeze, rinse with water, squeeze, and dry skein No. 1 for weighing.
2. Meanwhile prepare another bath containing 4 gm. of copperas (ferrous sulphate) in 400 cc. cold water. Work skein No. 2 in bath for 10 minutes cold. Remove, and rinse well; save the iron bath. Repeat the treatment in the sumach and iron baths several times more, finally wash the sumach iron skein in 1 per cent hot soap solution; rinse, squeeze, and dry. Weigh each dried and cooled skein and note the increase in weight of each. Save sample for Experiment [23] and note the effect of weighting on the yarn.
Experiment 23—Dyeing Silk
Apparatus: Porcelain dish, filter stand, etc.
Material: Piece of silk yarn.
Reference: Textiles, page [210].