Difficulty: Easy & Basic
Cotton can form a covalent bond with which common dye class?
A Acid dyes
B Reactive dyes
C Disperse dyes
D Basic dyes
Answer: B. Reactive dyes. Reactive dye groups can react with cellulose hydroxyl groups to form covalent bonds.
Stock dyeing takes place at what material stage?
A Finished garment
B Woven fabric
C Wound yarn package
D Loose fibre
Answer: D. Loose fibre. Stock dyeing colours loose fibres before yarn formation.
For dyeing wool from an acidic bath, which class is commonly chosen?
A Vat dyes
B Disperse dyes
C Direct dyes
D Acid dyes
Answer: D. Acid dyes. Anionic acid dyes can interact with protonated sites in wool and are commonly used for protein fibres.
During exhaust dyeing, shade develops as dye moves principally where?
A From liquor into fibre
B From package into air
C From fibre to drain
D From fabric to roller
Answer: A. From liquor into fibre. When a dyeing bath exhausts, dye is transferred from the solution or dispersion to the textile.
Inside cotton after vat dyeing, which step returns the dye to its insoluble form?
A Singeing
B Sequestering
C Desizing
D Oxidation
Answer: D. Oxidation. Oxidation converts the soluble leuco form back into the insoluble vat dye.
In garment dyeing, the item enters the dye bath in what form?
A Assembled article
B Fabric roll only
C Loose staple web
D Unwound polymer melt
Answer: A. Assembled article. Garment dyeing colours the garment after assembly.
Name the dye class used for many conventional acrylic fibres.
A Vat dyes
B Direct dyes
C Sulfur dyes
D Basic dyes
Answer: D. Basic dyes. Basic dyes are cationic and can bind to anionic sites in many acrylic fibres.
Fastness to light measures resistance to which change?
A Transfer caused by rubbing
B Tearing from a cut
C Fading from light exposure
D Length change in washing
Answer: C. Fading from light exposure. Light fastness describes how well the colour resists change when exposed to light.
Why is reactive-dyed cotton soaped or washed off after fixation?
A Remove loose dye
B Apply warp size
C Add another shade
D Increase fabric yarn count
Answer: A. Remove loose dye. Wash-off removes unfixed and hydrolysed dye that might otherwise stain other material or impair fastness.
Which colorant typically needs a binder to adhere to fabric?
A Reactive dye
B Acid dye
C Direct dye
D Pigment
Answer: D. Pigment. Pigment particles have little inherent fibre affinity and a binder holds them on the surface.
Where is colour first incorporated in solution dyeing of a manufactured fibre?
A Rinsing bath
B Polymer before extrusion
C Garment seam
D Finished fabric face
Answer: B. Polymer before extrusion. Colorant is mixed into the spinning solution or polymer melt before the fibre is formed.
Identify the usual role of salt during conventional reactive exhaust dyeing of cotton.
A Act as a binder
B Destroy the dye colour
C Promote dye exhaustion
D Remove all cotton wax
Answer: C. Promote dye exhaustion. Salt can help anionic reactive dye transfer from the bath to cotton.
With reactive cotton dyeing, what does fixation mean?
A Dye bonds to cellulose
B Fabric reaches equilibrium humidity
C Alkali dissolves completely
D Dye collects in the drain
Answer: A. Dye bonds to cellulose. Fixation is the reaction of dye with cellulose to form the dye–fibre bond.
Direct dyes are commonly used for which textile substrate?
A Cotton
B Polypropylene
C Conventional polyester
D Glass fibre
Answer: A. Cotton. Direct dyes have affinity for cellulose and can be applied from an aqueous bath.
Fabric has just been woven and is dyed as a roll. Which production stage is this?
A Stock dyeing
B Piece dyeing
C Solution dyeing
D Garment dyeing
Answer: B. Piece dyeing. Piece dyeing colours fabric after it has been woven or knitted and before it is made into an article.
Vat dyes must first become soluble. Which chemical change makes that possible?
A Mechanical rubbing
B Chemical reduction
C Ultraviolet exposure
D Chemical oxidation
Answer: B. Chemical reduction. Reduction in an alkaline bath generates the more soluble leuco form for application.
Why is a lab dip prepared before dyeing the full lot?
A Count machine revolutions
B Measure fabric tensile force
C Check the target shade
D Change the fibre identity
Answer: C. Check the target shade. A lab dip is a small trial used to assess shade and adjust the recipe before production.
Compare adsorption and diffusion in fibre dyeing. Which event describes dye moving inward from the surface?
A Oxidation
B Diffusion
C Adsorption
D Singeing
Answer: B. Diffusion. Adsorption occurs at the surface. Diffusion moves dye molecules into the fibre.
Dark cotton workwear can be coloured with which class widely used for economical black shades?
A Basic dyes
B Disperse dyes
C Sulfur dyes
D Acid dyes
Answer: C. Sulfur dyes. Sulfur dyes are widely used for economical deep shades, including black, on cellulosic materials.
When yarn is dyed before weaving, which design is readily made by arranging differently coloured yarns?
A Woven checks
B Uniform white fabric
C Random fibre pills
D Bonded nonwoven pores
Answer: A. Woven checks. Coloured warp and weft yarns can be arranged in repeating groups to form woven checks.
Hydrolysis of reactive dye occurs when the dye reacts with what?
A Dry pigment powder
B Gaseous nitrogen
C Water
D Only cotton fibres
Answer: C. Water. Hydrolysis is a side reaction with water. It consumes reactive groups that could otherwise bond to cellulose.
For conventional polyester, which dye class is most commonly used?
A Acid dyes
B Disperse dyes
C Sulfur dyes
D Direct dyes
Answer: B. Disperse dyes. Disperse dyes have low water solubility and can diffuse into polyester under suitable conditions.
On a dye recipe, shade at 2% owf is based on which mass?
A Total bath weight
B Dry weight of fibre
C Dye stock bottle weight
D Wet garment drain weight
Answer: B. Dry weight of fibre. The dye amount is expressed as a percentage of the dry textile mass.
For many reactive cotton dye systems, why is alkali dosed during fixation?
A Make polyester fibres dissolve
B Remove all water from bath
C Activate cellulose hydroxyl groups
D Oxidize all dye immediately
Answer: C. Activate cellulose hydroxyl groups. The alkaline condition increases cellulose reactivity so it can bond to the dye.
Level dyeing aims for which appearance?
A Lower fabric width
B Greater fibre twist
C More fabric seams
D Uniform shade
Answer: D. Uniform shade. Levelness means the colour is uniform across the textile or lot.