GATE (TF) Textile 2018 Question Paper Solution | GATE/2018/TF/18

Question 18 (Textile Technology & Fibre Science)

The discharging agent used in discharge printing of cotton with reactive dyes is

(A)Citric acid
(B)Sodium dithionite
(C)Thio-urea dioxide
(D)Sodium formaldehyde sulphoxylate
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Frequently Asked Questions | FAQs

What is discharge printing?

Discharge printing is a type of textile printing process in which a special water-based ink is used to remove or “discharge” the existing dye from a dark-colored fabric, leaving behind a light-colored print. This is achieved by adding a discharge agent, usually a mixture of a reducing agent and an activator, to the ink. The reducing agent breaks down the dye in the fabric, while the activator helps to neutralize the remaining dye and fix the ink.
Discharge printing is commonly used on dark-colored fabrics like black, navy, or dark brown, and is often used in the production of high-end t-shirts, sweatshirts, and other fashion garments. The resulting print has a soft, vintage feel and is often used for distressed or retro-style designs. The process can be used on a variety of fabrics, including cotton, rayon, and polyester, but it is most effective on fabrics that have been dyed with reactive dyes.

Which chemical is used for discharge printing?

A discharge agent is used for discharge printing. The discharge agent is a mixture of chemicals that are used to remove the existing dye from dark-colored fabrics and create a light-colored print. The two main components of the discharge agent are a reducing agent and an activator. The reducing agent breaks down the dye molecules in the fabric, while the activator helps to neutralize the remaining dye and fix the ink. Some common chemicals used as a reducing agent in discharge printing include thiourea dioxide, sodium formaldehyde sulfoxylate, and zinc formaldehyde sulfoxylate, while common activators include sodium alginate, urea, and sodium bicarbonate. The specific discharge agent and chemicals used can vary depending on the fabric type, color, and desired final result

What is the importance of discharge printing?

Discharge printing is an important textile printing technique for a number of reasons:

1)Soft and breathable prints: Discharge prints have a soft, breathable feel on the fabric as the dye is removed from the fabric, leaving the print area with no additional ink buildup. This makes them more comfortable to wear, especially in hot and humid climates.

2)Bright and vibrant colors: Discharge printing can create bright and vibrant prints on dark-colored fabrics, which would be difficult to achieve with regular pigment or screen printing.

3)Eco-friendliness: Discharge printing is an eco-friendly alternative to traditional printing methods because it does not use harsh chemicals or pigments. It removes the existing dye from the fabric, so there is less waste and water pollution compared to other printing methods.

4)Durability: Discharge prints are generally more durable than regular screen prints because the ink is absorbed into the fabric, rather than sitting on top of it. This makes them less likely to fade or crack over time.

5)Versatility: Discharge printing can be used on a wide range of fabrics, including cotton, rayon, and polyester. It can also be used to create a variety of effects, including vintage, distressed, and retro-style designs.

Overall, discharge printing is an important technique for creating high-quality, eco-friendly, and durable textile prints that are both comfortable to wear and visually appealing.

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