Bleach and printed cotton: what chlorine and oxygen bleach do
Chlorine and oxygen bleach both remove colour, but not in the same way or to the same degree. Here is what each does to printed cotton.
Bleach is the cause of a large share of complaints about faded or patchy printed textiles, particularly in hospitality, where commercial laundries use it routinely. Knowing what each type of bleach does to the colour and to the cotton itself helps buyers choose the right print process and write a care label that matches real use.
Two kinds of bleach
Chlorine bleach is sodium hypochlorite, the liquid sold as household bleach. It is a strong oxidising agent that works quickly even in cold water. Oxygen bleach is based on hydrogen peroxide, often supplied as sodium percarbonate powder in detergents and stain removers. It is gentler, works best in warm to hot water, and is often boosted by an activator so that it works at lower temperatures.
What chlorine does to printed cotton
- Colour. Hypochlorite attacks the chromophore, the part of a dye molecule that gives colour. Many reactive dyes, which give cotton its deepest and softest prints, have only moderate resistance to chlorine. Contact with neat or strong bleach leaves pale or white spots; repeated dilute use causes gradual, overall fading.
- Fibre. Chlorine also oxidises cellulose. Repeated use weakens cotton, lowering tear and abrasion strength, and the damage is invisible until the cloth splits.
- Other fibres and finishes. Elastane yellows and loses stretch with chlorine. Some resin and softener finishes can yellow as well.
What oxygen bleach does
Oxygen bleach is described as colour-safe, and for most well-fixed reactive dyes and pigments it largely is at normal use. It is not harmless, however. At high temperatures, high concentrations or with strong activators, it fades some shades, particularly bright turquoises and certain reds. It is also far kinder to the fibre than chlorine, which is why it is the better choice for printed cotton that needs whitening or stain removal.
Pigment prints and reactive prints
Pigments are insoluble coloured particles held on the fibre by a binder. Many pigments resist oxidising agents better than many reactive dyes, but the result depends on the individual pigment, and aggressive chemistry and heavy mechanical action wear the binder film over time. Reactive prints behave like dyed cotton: excellent in normal washing, vulnerable to chlorine. Neither process makes a printed textile truly bleach-proof, and the safe course is to test the actual colours.
How bleach fastness is tested
Colour fastness to hypochlorite bleaching is covered by ISO 105-N01, which grades the change in colour after treatment in a bleach solution. Some procedures within ISO 105-C06, the washing fastness standard, include a perborate or other oxygen bleach in the wash liquor, which gives an idea of how colours respond to detergents containing oxygen bleach. Ask for results on the specific shades in your design, not just a general statement about the dye class.
Care symbols
- An empty triangle means any bleach may be used.
- A triangle with two diagonal lines means only oxygen or non-chlorine bleach.
- A crossed-out triangle means do not bleach.
For most printed cotton, the triangle with two lines is the honest label. For items that will go through commercial laundries, confirm the laundry's process before choosing colours, and consider plain or piece-dyed items in shades with good chlorine fastness for products that must be bleached.
Practical advice
Never pour bleach directly onto printed fabric, never mix chlorine bleach with other cleaning products, and rinse thoroughly after any bleach use. When whites and prints share a laundry, wash them separately. If you are planning printed tea towels, aprons or table linen for heavy laundering, compare reactive digital printing and pigment rotary printing, and send us the laundry conditions through our contact page so that colours can be tested before bulk.
