Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY IDENTIFICATION OF FIBRES BY MICROSCOPY 1 Objectives....................................................................................2 2 Theoretical introduction...............................................................3 3 Materials, equipments and working tools....................................5 4 Experimental procedure...............................................................6 5 Safety and work specific rules...................................................9 6 Instructions to write the report …………………………………10 7 Additional information ................................................................12 1/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY 1. Objectives 1.1. Didactic • Characterizing the fabrics attending to their composition. • Getting fibres out of the fabrics and creating preparations to put them under the microscope. • Distinguishing between natural and manufactured fibres (artificial and synthetic). • Distinguishing and identifying the natural fibres more frequently used in the textile industry: cotton, linen, silk, wool and others. • Knowing the morphology of the most frequently used natural fibres. 2/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY 2. Theoretical introduction Fabrics are made up of yarns that, for their part, are elaborated by means of fibres, filaments and, in some occasions, by both. In order to analyze the fibres of a fabric it will be necessary, in the first place, to draw the yarns out of the fabric and, in the second place, to draw the fibres out of the yarns. Weft and warp may have different kinds of yarns. It is also possible to use several kinds of yarns in the same weft and / or warp. All these things must be taken into account when analyzing the fabrics, being necessary to take yarns from warp separately from weft. When the yarns have been drawn out of the weft and of the warp, getting fibres or filaments individually will suppose to do by hand the inverse process to the spinning: untwisting for the separation of the fibres. Once we get the fibre it is put onto the slide to be observed under the microscope. Natural fibres can be distinguished under the microscope by the characteristic outline they present. We have three different kinds of fibres of animal origin: wools, hairs and silks. In the case of the woollen fibres they come from the sheep. They have a characteristic stretch- marked outline (see Image 1) that gives them different qualities, as the easiness of forming felts. Sometimes they can cause skin irritation. Silks come from worms that secrete a filament with which they make a cocoon. They belong to the so called secretion fibres and have a similarity with the synthetic fibres of continual filament obtained through a process of extrusion. They have a smooth surface with some irregularities and these make them to look different to the synthetic ones that are more regular. In the image 2 we can see the smoothness of the silk fibre and some narrowing of it in some areas. Figure1. Wool. Lengthwise sight 100X Figure2. Silk. Lengthwise sight 100X 3/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY There is a great variety of fibres of vegetal origin. They may come from seeds, stems and leaves. The most frequently used in clothing are cotton and linen, which come from seeds and stems respectively. The cotton fibres show convolutions or folds like a twisted ribbon. These are produced when the cotton is mature; the central canal of the fibre is collapsed and it is created a twist that makes easier the cohesion of ones to the others facilitating the process of spinning. Linen is a resistant fibre. Its look is similar to a cane because of the transversal lines called nodes, which can be seen along the whole fibre and which are its distinctive feature. Figure3. Cotton. Longitudinal sight 100X Figure4. Linen. Longitudinal sight 100X The microscope allows us to see the fibres enlarged. The magnification of the microscope is defined as the relation between the seeming diameter or length of the image and the real diameter or length of the object. This means that if the microscope magnifies an object 100 its diameter, the image that we are looking at is 100 times bigger in linear terms, but in terms of surface it will be 1002, that is to say, 10,000 times bigger. To calculate the linear magnification given by the microscope we have to multiply the respective magnifications owed to the objective lens and the eyepiece used. For instance, if we are using an objective lens of 40X and an eyepiece lens of 10X, the linear magnification which we are looking at the sample with will be 400 times (400X). 4/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY 3. Materials, equipments and working tools 3.1 Materials • 1ml of propane (acetone) • 1 drop Canadian balm. • 25cm1ml of propane (acetone) • 1 drop Canadian balm. • 25cm1ml of propane (acetone) • 1 drop Canadian balm. • 25cm of cloths of natural fibres of vegetal origin: * From stem. For instance: linen, hemp, ramie. * From seed. For instance: cotton. * From leaf. For instance: pita. • 25 cm2 of fabrics of natural fibre of animal origin: * From hair follicle. For example: sheep, camel and angora hair. * From gland: For example: silk. • 25cm2 of fabrics of artificial and synthetic fibres. - Artificial: for example rayon and acetate. - Synthetic: for example polyester, polyamide. 3.2 Equipments and working tools. 5/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY Figure 5. Yarns counter (unfinished image to settle) • 1 optic microscope of refraction. • 1 set of microscope slides and slide covers. • 1 camera for the microscope. • 1 steel tweezers • 1 punch or pin. • 1 scissors • 1 threads counter or magnifying glass. • 1 computer. 6/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY 4. Experimental procedure. Nº of students: 1 Time: 4 hours. Per each sample of cloth: a) Visual study of the cloth and drawing out of yarns We draw out some samples of yarn from weft and from warp separately, each sample of about two or three yarns. Figure 6. Drawing out of yarns from weft and warp from the fabric. If we observe different types of yarns in weft and/or in warp we’ll draw out so many samples as kinds of yarns we find. b) Preparations for using the microscope. I. Preparing so many microscope slides and slide covers as samples of yarns we have. II. Identifying with a felt-tip pen each slide with the reference: fabric sample (for example F1, F2, F3…) + yarn sample ( for example Y1,Y2,…) + the initial of the student’s name. The identification would be, for example. F1- Y2- AAA. III. Dripping one drop of Canadian balm onto the middle of the slide, with the help of the rod of the bottle. 7/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY IV. Extract the single fibres of the selected yarns, twisting them in the opposite direction to their own twist ( if we do it in the same direction in which the yarn is twisted it will become curly) and pulling slightly with the purpose of taking them apart so that we can draw out easily the fibres that make them up. Figure 7. Extraction of single fibres yarn. V. When the fibres are accessible, with the help of metallic tweezers, take one or two fibres and put them on the Canadian balm placed on the marked glass slide. VI. Then hold the slide cover by its edges and place it on the glass slide so that one of its sides gets in contact with the drop and place it slowly on the slide till they are completely leaned on each other. VII. Once the slide cover is completely leaned on the slide press gently, with the help of the tweezers, so that the Canadian balm is spread all over its surface. It is very important to do everything like described before with the aim of avoiding, as much as possible, the appearance of bubbles, fingerprints, dust, etc. in the preparation, as those would interfere in the observation. 8/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY C/ Study of the sample under the microscope. I. Starting the exploration with the x4 objective, as it will give us 40 magnifications. II. Register photographs of the sample and file it in the computer with its identification: fabric sample (for example: F1, F2, F3…) + yarn sample (Y1, Y2, Y3…) + the student’s name initials + amplification of the image. The identification would result, for instance: F1-Y2-AAA-40X III. Going on with the exploration of the sample amplifying the enlargment; getting images 100X y 400X. 9/13 Comprehensive didactic development in the practice of textile technology IDENTIFICATION OF FIBRES BY MICROSCOPY 5 Safety and work specific rules 5.1 Safety and handling of equipments • Follow the instructions to use the microscope and the camera provided. • Take special care of not pushing anybody while looking at something under the microscope to avoid injuries. • Not to carry any product or glass inside your lab coat’s pockets. • Make sure all the appliances are switched off. • After finishing any task pick up all