How bamboo fabric is dyed
Short answer: Cellulose fibers are dyed with reactive dyes that bond chemically to the fiber. That gives good colorfastness, but the color still only holds as well as the process itself allows.
Chemical bonding
Reactive dyes form a chemical bond with the cellulose in the fiber instead of just sitting on top of it. It is exactly that bond that keeps the color from washing out during normal washing. See facts about bamboo for background on the fiber's structure and properties.
That is why new clothing releases color
Excess dye that has not fully bonded to the fiber washes out during the first few times a piece is washed. So wash new dark clothing on its own until the water no longer noticeably colors during washing.
Colorfastness varies
How well the color holds depends on which dye is used and how thoroughly the dyeing process itself was carried out at the factory. That is why two dark blue pieces from different makers can behave differently in the wash and in sunlight over time.
Sunlight breaks down color
No matter how good the bond is, dye molecules break down slowly from ultraviolet sunlight. Dry the clothing in shade rather than direct sun if you want to keep the color as long as possible. See bamboo underwear for women for items where colorfastness matters especially.
Wear is not the same as fading
Black clothing that turns dull over time is often due to a worn surface rather than actual color loss in the fiber. The two can look similar but need different care to avoid or reduce them going forward.
The role of temperature in dyeing
Reactive dyes bond best at a specific temperature during production itself, which is one reason the dyeing process is hard to replicate at home with the same result as at the factory. See bamboo underwear for men for examples of evenly, factory-dyed fabric.
How to keep the color best
Wash at low temperature, avoid direct sun while drying, and turn dark clothing inside out in the washing machine. See washing and care for the full recommendations for keeping both color and fabric strength intact.
Difference between light and dark colors
Light colors need less dye and therefore rarely show signs of fading, while dark colors such as black and navy are more sensitive to both sunlight and frequent washing at high temperature.
In short
Bamboo fabric is dyed with reactive dyes that bond chemically to the cellulose. New dark clothing may release a little color at first, and sunlight breaks down color over time. Wash at low temperature and dry in shade, and the color lasts the longest.
Frequently asked questions
How is bamboo fabric dyed?
With reactive dyes that bond chemically to the cellulose in the fiber, instead of just sitting on the surface as with some other dyeing methods.
Why does new clothing release color?
Because excess dye that has not fully bonded to the fiber washes out during the first few times a piece goes through the machine.
Can the color fade?
Yes, from sunlight over time. Wear on the surface is a different thing and can look like fading, but comes from the fabric's structure rather than the dye.
You can find the full range at Bamboo-Clothing.com.
