Dyeing fashionable bright blue shades on cellulosic fibres

1. Abstract

Often people ask about the problems encountered in dyeing bright blue shades on cellulosic substrates, particularly cotton and viscose. The following question comes from Dyehouses in Peru and Brazil.

"We are having problems dyeing bright blue shades. We can see red areas across and throughout the fabric. Do you know what could be the problem?"

This article seeks to consider some of the critical issues involved.

2. Full Article

2.1 The Solution

The solution comes from the Dye House Solution as follows

There are many examples of such patchy red areas in dyeing with reactive bright blue dyes.

However, they have diagnosed different origins to each problem. Each case must be treated on its individual merits. Some clues as to the origin of the problem can be gleaned by circumstances surrounding the observed problem.

2.2 Most Widely Used Dyes

Table 1: Largest Global Dye Sales

2.3 Shade Sensitivities of Bright Blue Reactive Dyes

• The following comments relate to dyes provided by major European or Japanese suppliers. For those dyes sold on the basis of Colour Index number, there can be no guarantee of product quality, constitution, impurities or that they do not suffer additional sensitivities.

• Given the above reservation, a number of sensitivities have been observed:

• pH: Acid sends the shade red. Red patches can be due to uneven softening at acidic pH.
• Temperature: Higher temperature sends the shade redder - so allow fabric to fully condition (or stream calendar) before inspection.
• Alkaline Earth Metals: Ca and Mg (and to a lesser extent Mn) both cause a shade shift to red. (See Case Study 1).
• Gaseous oxides of Nitrogen: Gas fire stenters are notorious for producing such problems in the Dyehouse; gas fired heaters and stoves in fabric and garment storage and vehicle exhaust fumes in loading bays.

• The problem can therefore occur at different stages of wet processing and garment confection and delivery