Care and Maintenance of FabricsClass 11 Human Ecology And Family Sciences Part 2 NCERT Solutions
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Q1Review Questions
What are the different aspects of care and maintenance of fabrics?
Solution
The different aspects of care and maintenance of fabrics are aimed at retaining the material's quality, appearance, and functionality for its expected life. Based on the chapter, these aspects include:
- Mending: This involves keeping the material free from physical damage by repairing cuts, tears, holes, replacing fasteners, and restitching seams and hems. It is essential to perform mending before laundering to prevent further damage.
- Retaining Appearance: This is a crucial aspect and involves several processes:
- Stain and Dirt Removal: Cleaning the fabric to remove unwanted marks and dirt without damaging its colour or texture.
- Retaining Brightness and Texture: Using finishing treatments like blueing and starching to restore whiteness, brightness, and textural qualities such as softness, stiffness, or crispness.
- Wrinkle Management: Ironing or pressing the fabric to keep it free of wrinkles and to add or retain creases where required for a neat appearance.
Q2Review Questions
Define the term 'stain'. What are the different types of stains and what techniques can be used for removing them?
Solution
Definition of a Stain:
A stain is defined as an unwanted mark or colouration on a fabric caused by the contact and absorption of foreign matter. It cannot be removed by the normal washing process and requires special treatment.
Types of Stains:
The chapter classifies stains into five main categories based on their origin:
- Vegetable Stains: Caused by tea, coffee, fruits, and vegetables. They are acidic and can be removed by an alkaline medium.
- Animal Stains: Caused by blood, milk, meat, and eggs. These are protein-based and are removed with detergents in cold water.
- Oil Stains: Caused by oils, ghee, and butter. These are removed using grease solvents and absorbents.
- Mineral Stains: Caused by ink, rust, and medicine. These should be treated first with an acidic medium and then an alkaline medium.
- Dye Bleeding: Colour transferred from other fabrics. These can be removed with dilute alkalies or acids, depending on the fabric.
Techniques for Stain Removal:
Four primary techniques are used for applying reagents to remove stains:
- Scraping: Using a blunt knife to lightly scrape off built-up surface stains.
- Dipping: Immersing and scrubbing the stained portion of the material in a reagent.
- Sponging: Placing the stained area on a flat surface over a blotting paper and applying the reagent with a sponge.
- Drop Method: Stretching the stained cloth over a bowl and applying the reagent onto the stain using a dropper.
Q3Review Questions
Write the steps in removing unknown stains from fabrics.
Solution
When dealing with an unknown stain, it is crucial to proceed with caution to avoid setting the stain or damaging the fabric. The general considerations provided in the chapter suggest the following steps:
- Act Quickly: A stain is best removed when it is fresh. The longer it sets, the harder it is to remove.
- Start with a Simple Process: Begin with the mildest treatment possible. For many unknown stains, this could be sponging or rinsing with cold water.
- Move to a Complex Process Gradually: If the simple process does not work, move to a slightly stronger but still mild reagent. The principle is that repeated use of a milder reagent is better and safer for the fabric than a single application of a strong agent.
- Test the Reagent: Before applying any chemical or stain remover to the visible part of the stain, test it on a small, inconspicuous portion of the fabric (like an inner seam or hem) to ensure it does not damage the colour or the fibre.
- Wash After Treatment: After the stain has been removed, the entire fabric should be washed with a soapy solution to remove all traces of the chemical reagent used.
- Use Sunlight: For white fabrics, drying in the sun can be beneficial as sunlight acts as a natural bleaching agent.
Q4Review Questions
What is dirt? How do water, soaps and detergents combine to remove dirt from fabrics?
Solution
Definition of Dirt:
Dirt is the term for grease, grime, and dust that is jammed within the fabric's structure. There are two types: loose dirt, which can be easily shaken or brushed off, and tightly held dirt, which is bound to the fabric by sweat and grease and requires a more thorough cleaning process.
How Water, Soaps, and Detergents Remove Dirt:
The combination of water, soaps, and detergents works through a multi-step process to effectively clean fabrics:
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Role of Water: Water is the primary agent in laundry. During steeping, it penetrates the fabric, causing it to get wet. The movement of water particles (pedesis) helps to dislodge and remove loose, non-greasy dirt. However, water alone cannot remove greasy dirt and cannot keep removed dirt suspended, which can lead to it redepositing on the fabric, causing grayness.
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Role of Soaps and Detergents (Surfactants): Soaps and detergents are surface-active agents, or surfactants. Their function is two-fold:
- Reducing Surface Tension: They reduce the surface tension of water, allowing it to penetrate the fabric more easily and effectively, thus reaching the dirt faster.
- Emulsifying Grease: They have a chemical structure that allows them to attach to both water and grease. They break down the grease holding the dirt into very small particles, a process called emulsification. This loosens the dirt's grip on the fabric fibres.
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Suspension and Rinsing: Once the dirt is loosened, the surfactants in soaps and detergents keep these dirt and grease particles suspended in the wash water. This is a critical step as it prevents the dirt from being redeposited back onto the clean fabric. The suspended dirt is then washed away during the rinsing process, leaving the fabric clean.
Q5Review Questions
How does finishing after washing improve the brightness and textural characteristics of fabrics?
Solution
Finishing is an important step in the laundering process that takes place after washing and rinsing. It helps restore the original appearance of the fabric by improving its brightness and textural characteristics.
Improving Brightness:
Repeated washing can cause white fabrics to become yellow or gray. Finishing agents counteract this discolouration.
- Blues: These are used to counteract the yellowness that often develops in white cotton articles. Ultramarine blue (powder) or liquid chemical dyes are added to the final rinse water, making the fabric appear whiter.
- Optical Brighteners: These are fluorescent compounds that absorb invisible ultraviolet light and re-emit it as visible blue light. This gives the fabric an intense bright whiteness, which can counteract both yellowness and grayness. They are effective on both white and coloured fabrics.
Improving Textural Characteristics:
Laundering can cause fabrics to lose their body, stiffness, and shine. Stiffening agents are used to restore these qualities.
- Starching: This is the most common technique to make cotton and linen fabrics firm, smooth, and shiny. Starch (from rice, wheat, etc.) is applied to the fabric, which not only enhances its appearance and texture but also makes subsequent washing easier as dirt clings to the starch instead of the fabric.
- Other Stiffening Agents: For delicate fabrics like silk and rayon, other agents are used. Gum Acacia provides light crispness, while gelatin can also be used. Adding borax to a starch solution helps it form a thin, water-repellent film when ironed, maintaining crispness even in humid conditions.
Q6Review Questions
What is dry-cleaning? What are the types of fabrics where dry-cleaning is recommended?
Solution
Definition of Dry-cleaning:
Dry-cleaning is a process of cleaning fabrics using a non-aqueous liquid medium, meaning a solvent other than water. Common solvents include perchloro-ethylene or petroleum solvents. The main advantage of dry-cleaning is that these solvents do not cause fibres to swell, which prevents issues common with water-based washing like shrinkage, wrinkle formation, and colour bleeding. This makes it a safe cleaning method for delicate textiles.
Types of Fabrics Recommended for Dry-cleaning:
Dry-cleaning is recommended for fabrics that are sensitive to water, heat, or the mechanical agitation of a normal wash. Based on the chapter, these include:
- Wool: Wool fibres are weak when wet and have a tendency to felt and shrink when agitated in water. The text states that dry-cleaning solvents have no harmful effect on wool, making it the preferred method for cleaning woolen garments.
- Silk: Silk is a strong fibre but weakens when wet, requiring careful handling. It can also be damaged by strong alkalis found in some detergents. Perspiration can damage silk, so the text recommends that it should be dry-cleaned before storage. Dry-cleaning solvents do not harm silk.
- Rayon: Many rayon fabrics are weak, especially when wet, and are prone to shrinking and wrinkling. Dry-cleaning is often a safer option to maintain their shape and texture.
- Delicate Textiles: In general, any delicate fabric with a special finish, complex weave (like those with long floats), or embellishments that could be damaged by water and friction is a candidate for dry-cleaning.