And rive-centre would be "horizontally"

Cf.:

« En général, les colorants à faible affinité sont préférables dans la teinture à la continu afin d'empêcher les risques de queutage ("tailing": écart de nuance de teinture entre le début et la fin de la pièce attribuable à l'épuisement non désiré de la solution de foulardage) et faciliter le lavage du colorant non fixé. »
(http://www.ineris.fr/ippc/sites/default/interactive/bref_tex...

“In general, dyes with low affinity are favoured in continuous dyeing to prevent tailing (attributable to undesirable exhaustion of the padding solution) and to make washing-off of the unfixed dye easier.”
(http://www.ineris.fr/ippc/sites/default/interactive/bref_tex...


“What are right practices of Continuous and Semi Continuous process of woven cotton fabric, from preparation to reactive dyeing? What are reasons for the following problems and how they can be taken care of?

Problems:

1. Tailing
2. C/S variation (Center to selvedge)
3. Back to Face variation
4. Lot to Lot variation
5. Specks and spots in dyeing.”

“Possible Faults that may occur during the above process and check points/rectification:

1. Tailing: The Alkalinity in the mercerized fabric would be un-uniform ranging from 0.25 to 1 and above gram/liter due to inefficient recuperation. That means more and more alkalinity would be carried over on the mercerized cloth and that can be checked in lab by titration. Any variation in the alkalinity of the mercerized fabric can show up through the length by the dye affinity difference and that is tailing.
a. Check Point:
i. Alkalinity of the mercerized cloth has to be quantitatively checked in the lab at intervals of 500 meters. It must be uniform.

2. C/S Variation – may arise due to
a. Desizing – Expression of the squeezing mangle is to be checked at frequent intervals.
b. Caustic Impregnation - Expression of the squeezing mangle is to be checked at frequent intervals.
c. Peroxide Bleaching:
i. Steam Pressure
ii. Steam Temperature
iii. Time duration of the steaming are to be controlled.
ii. Mercerising – Impregnation Mangle expression has to be checked.
1. Recuperator Efficiency has to be checked at every 1000 meters.
2. Final Alkalinity of the mercerized fabric should be less than 0.25 g/l of caustic.
3. Soaper washing – Acid for neutralization should be prepared in volume and should be fed in to the neutralization tank continuously.
4. To counter check, the fabric absorbency may be checked in the center and the two selvedges at regular intervals.”
(http://www.thesmarttime.com/faq/continuous-dyeing.htm)