The pupils should be asked to give instances from their own experience where special solvents were used to remove stains, and be required to make a list of these. If necessary, the teacher should supplement this list with the names of other agents and the methods of using them. OUTLINE OF LESSONS ON THE WASHING OF WOOLLENS The washing of woollen materials is part of the Course for the work of the Senior Grade of Form IV, but, for the sake of convenience, the laundry lessons of both Grades of Form IV are outlined in one section of this Manual. Before allowing the class any practice in this branch of laundry work, it will be necessary for the teacher to make certain principles very clear: 1. That wool is an animal product. As such it tends to be shrunken and hardened by (1) heat, (2) alkalies. 2. That the surface of each wool fibre woven into woollen materials is seen under the microscope to be covered with notches, or scales. If these notches in any way become entangled, the material is thereby drawn up, or "shrunken". 3. That these notches may be entangled by: (1) Wetting the woollen material and then rubbing or twisting it. When the fibres are wet, they expand somewhat and the projecting scales, or notches, are loosened. If the material is rubbed at this time, the notched edges interlock. (2) The use of strong soaps or alkalies. These act chemically on the fibres and soften and expand them, causing the notched edges to become so prominent that they catch in one another. NOTE.--The structure of woollen fibres may be sketched on the black-board and compared with those of cotton and linen. To impress the foregoing principles, a few experiments will be found most useful. EXPERIMENTS WITH CLOTH MADE OF WOOL FIBRE 1. Boil a piece of new woollen cloth for five minutes. Dry, and compare with an original piece. 2. Saturate a piece of new woollen cloth with a strong solution of washing soda. Dry, and compare with an original piece. 3. Wash a piece of new woollen cloth in each of the following ways: (1) By rubbing soap directly on the cloth and then sousing the goods in the water. (2) By using a soap solution instead of the soap, as in (1). (3) By rubbing on a wash-board. In each case dry the cloth and compare with an original piece. After the results of the experiments have been discussed, the pupils may formulate a series of "points" to be observed in the washing of woollen fabrics. [Illustration: Cotton fibres magnified] [Illustration: Linen fibres magnified] [Illustration: Woollen fibres magnified] POINTS IN WASHING WOOLLENS 1. Use lukewarm, soft water. 2. Do not use strong soaps or alkalies. 3. Do not rub soap directly on the woollen material, but use soap solutions. 4. Do not rub or twist woollen cloth when it is wet.