Teasels, or Teazels.—Thistleheads with curved bracts, used in cloth raising.
Terry Cloth.—A weave in looped effect. A Velvet in which the loops have not been cut. Frequently applied to cotton fabrics of the order of Agaric and Sponge Cloth. [See Turkish Towelling].
Tests by Burning.—Yarns or fibres of different origin burn in different manner. Cotton, linen, ramie, rhea, china grass, etc., ignite and burn readily with a bright smokeless and odourless flame, leaving but a small amount of ash, this being the characteristic of vegetable fibres. Animal fibres, on the other hand, are slower to ignite, the appearance of the flame is lifeless, and the fibres burn more slowly than vegetable fibres. Wool, when burnt, emits a disagreeable odour, and the residue or ash takes the form of a bead or knob. Silk burns in the same way as wool when it is free of "weighting." When artificially weighted, silk may have its weight increased to almost any desired extent—from 80 to 200 per cent. increase in weight can be obtained without creating suspicion. When such weighted silk is burnt, instead of forming itself into small black beads or knobs, it burns leaving a distinct ash, which retains somewhat the shape of the original material. Artificial or cellulose silk burns readily and in burning does not give off any odour.
Test for Artificial Silk.—The burning test should in most cases be sufficient to distinguish artificial from true silk, but if a chemical test is necessary, by immersing the suspect sample in a caustic potash solution it will be seen that artificial silk turns yellow, whereas true silk does not change colour. Artificial silk, which is a nitro-cellulose, burns very rapidly, leaving practically no ash whatever. A simple way of recognising artificial silk is by testing the threads under moisture. Unravel a few threads of the suspected fabric and place them in the mouth and masticate them thoroughly. Artificial silk readily softens under this operation and breaks up into minute particles, and when pulled between the fingers shows no thread, but merely a mass of cellulose or pulp. Natural silk, no matter how thoroughly masticated, will retain its fibrous strength.
Tests for Linen.—Linen, like cotton, burns when a light is applied, leaving a white ash. Linen yarns are more irregular in their thickness longitudinally than cotton thread taken from similar woven fabrics. This difference makes the detection of linen in a woven cloth comparatively easy. The fibres are straighter, longer, and stronger when separated in the thread than cotton. The threads often snap sharp and clear when breaking them in the fingers. The oil test for linen is based upon the property which linen has of more readily absorbing oil than cotton does. When a linen and cotton mixture fabric which has been freed from dressing by washing and boiling is dipped in oil and then held up to the light it will be seen that the linen fibres look transparent, whereas the cotton remains more nearly opaque. This is due to the linen having absorbed the oil more readily than the cotton. All the cotton contained in a linen and cotton fabric can be readily dissolved by dipping the fabric in a concentrated sulphuric acid bath for one or two minutes. The sample is first freed of dressing. After washing and drying a sample so tested the linen fibre only will remain.
Test for Mercerised Cotton.—Prepare a solution made by dissolving 1¼ ounces of iodide of potassium in 5 ounces of water, then add to this solution ½ ounce of iodine, and mix with another solution made by dissolving 7½ ounces of zinc chloride in 3 ounces of water. The test is applied as follows: take the suspect sample and free it from any dressing or sizing by soaking it in water; then, after freeing the sample from any superfluous water, place it in some of the prepared solution for three minutes, and then rinse the sample in water. Should the cotton tested have been mercerised it will appear of a deep blue colour. On washing with water the blue colour fades very slowly and needs long washing, whereas ordinary cotton rapidly becomes white on washing. Even dyed piece goods will show the deep blue reaction, which is the result of the testing solution acting upon the caustic soda used in the process of mercerisation. When making this test it is best to treat a "known" unmercerised cotton at the same time as the suspect sample so as to have a basis for comparison.
Tests for Silk.—If a silk and wool mixture or union fabric is boiled in strong hydrochloric acid for 15 minutes, it will be found that the wool merely swells, whilst the silk acted upon by the acid completely dissolves. By careful weighing before and after the test it becomes a matter of simple calculation to arrive at the percentage of silk present in the fabric.
Test for Wool.—If a fabric suspected of containing wool and cotton or other vegetable fibre is boiled for 15 minutes in a solution made by dissolving either 1 ounce of caustic soda or caustic potash in a pint of water it will be found that all the wool will be destroyed and only the vegetable fibres remain. This test, which is based upon the well-known fact that caustic soda dissolves wool, may be used to ascertain the percentage of wool in a cloth if the sample tested is thoroughly washed, dried, and weighed before the test is applied. After testing and drying, the loss in weight represents the amount of wool which was present and destroyed during the test. This test may be reversed and the cotton destroyed by treating the sample with an 80 per cent. sulphuric acid solution. This, however, is a longer test, necessitating the sample being kept in the sulphuric acid solution for about 10 or 12 hours. Prior to drying and weighing the sample should be well washed in alcohol.