A rotary screen has a circumference of 640 millimetres. What is the longest repeat it can print?
Answer: A
The repeat cannot exceed the circumference, since the design must join seamlessly as the cylinder turns. Standard circumferences are chosen so that common repeat lengths divide into them exactly. Longer designs need a flat screen instead.
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Fixation of a printed reactive design is normally carried out by
Answer: B
Correct answer: steaming the dried print
Steaming supplies both the heat and the moisture the fixation needs: the water condensing in the print film dissolves the dye and the alkali, letting the dye migrate into the swollen fibre and react with it. Ten minutes of saturated steam is typical. Washing at this stage would strip the unfixed dye away before it had a chance to react.
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Consider the following statements about washing off a printed fabric.
1. The thickener and unfixed dye must both be removed.
2. Poor washing off leaves a stiff handle and poor rub fastness.
3. Washing off is unnecessary after transfer printing.
Answer: C
Correct answer: All of them
All three are correct. The thickener and any unreacted dye must be removed, or the fabric is left stiff and the loose dye rubs off, so poor washing off shows as both a harsh handle and poor rub fastness. And transfer printing genuinely needs no washing off, because the dye sublimes directly into the fibre with no thickener and no unfixed residue on the surface - one of that process’s main attractions.
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Pigment printing differs from dye printing in that the colour is
Answer: D
Correct answer: held on the surface by a binder
A pigment has no affinity for any fibre; it is an insoluble coloured particle glued to the surface by a polymer binder that is cured by dry heat. That makes the process simple and cheap - no steaming and no washing off - and it accounts for its weaknesses too: a stiffer handle and rub fastness dependent entirely on the binder film.
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Assertion (A): Pigment printing can be used on any fibre.
Reason (R): The pigment is held by a binder film rather than by affinity for the fibre.
Answer: A
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the cause. Because the colour is held mechanically by a binder rather than by any chemical or physical affinity, the fibre beneath is irrelevant - cotton, polyester, blends and even non-textiles print alike. That universality is why pigment printing accounts for the majority of textile printing worldwide despite its handle and fastness limitations.
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State whether the following is true or false.
Pigment printing requires no washing off after fixation.
Answer: B
There is no thickener to remove and no unfixed dye, so curing the binder completes the process. This saves a great deal of water and is the main economic argument for the route. Curing replaces steaming and washing together.
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Side to centre variation in a printed fabric usually points to
Answer: C
Pressure decides paste transfer, so a gradient across the machine appears directly as a shade gradient. Checking and setting the squeegee is a routine part of starting a run. The fault appears as a gradient across the piece.
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