Uneven mercerisation shows itself most obviously as
Answer: A
The variation in accessibility translates directly into variation in shade, which the eye picks up readily. The fault often traces back to uneven impregnation or uneven tension across the width. The fault appears only after dyeing.
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Consider the following statements about faults in mercerising.
1. Uneven impregnation gives patchy dyeing later.
2. Uneven tension across the width gives a variation in lustre.
3. A fault in mercerising can be corrected by re-dyeing.
Answer: B
Correct answer: 1 and 2 only
Statements 1 and 2 are correct: uneven impregnation shows later as patchy dyeing, and uneven tension across the width shows as a variation in lustre from selvedge to selvedge. Statement 3 is wrong, and it is the point worth taking - mercerisation changes the fibre structure permanently, so a fault in it cannot be dyed out and the cloth is downgraded.
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State whether the following is true or false.
A mercerising fault can usually be corrected by adjusting the dyeing recipe.
Answer: C
The variation lies in how accessible the fibre is, so every dye applied afterwards reproduces the same pattern. Re-mercerising is occasionally attempted but rarely evens out the original fault. The variation lies in the fibre rather than the dye.
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Neutralisation after mercerising is carried out with
Answer: D
Residual alkali would interfere with dyeing and could damage the fabric in storage. The rinse must bring the fabric genuinely to neutral rather than merely close to it. Dried fabric pH is checked as a matter of course.
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Assertion (A): Residual alkali must be removed completely after mercerising.
Reason (R): Alkali left in the fabric interferes with dyeing and can degrade the cellulose in storage.
Answer: A
Both are true and the reason gives both consequences: the pH of the dried fabric is a routine quality check for exactly this reason, and a piece that fails it goes back for further rinsing rather than forward to the dyehouse.
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Chainless mercerising differs from chain mercerising in that
Answer: B
Correct answer: tension is applied by rollers
Chain mercerising grips the selvedges on a stenter chain and holds the fabric to width; chainless mercerising applies the tension through a series of driven rollers instead. The chainless machine is simpler and faster and avoids selvedge damage, but it can hold the *length* under tension rather better than the width, so it suits some constructions and not others.
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