Experiment 44—Test for Vegetable and Animal Fiber
Apparatus: Acid, fire.
Materials: Warp and filling threads of cotton and woolen fabrics.
Reference: Textiles, page [239].
Directions
One of the most useful tests is to see whether an article is made of wool, cotton, or silk, and if a composition of two or more materials, to estimate the percentage of each. Practical experience can teach one much in this respect, and in many cases inspection is quite insufficient. A more reliable test is to burn a piece of material and notice how it burns.
Take a sample of a woolen and cotton fabric; separate the warp and filling and untwist one piece of warp and one piece of filling yarn. Burn a piece of untwisted yarn and notice whether it burns slowly and curls up into a black crisp cinder leaving a disagreeable smell, or burns with a flash leaving a light ash behind.
Questions
1. Describe the burning process.
2. What is the burning test for vegetable fiber?
3. What is the burning test for animal fiber?
Repeat the same experiment, placing the untwisted yarn in sulphuric acid. Apply heat and note the effect.