Name: cnsathya
Message: Dear Sir, I like to dye cotton yarn in turmeric but came to know it is light fastness is poor. How to improve the light fastness for turmeric dyes.

Turmeric, an inexpensive spice which makes an intensely yellow dye for natural fibers and nylon, is inherently non-lightfast. The only solutions are to store turmeric-dyed items in the dark, keep them out of bright sunlight as much as possible, wash and dry the dyed items  indoors, and then plan on redyeing them every year or so.

Disappointingly, ultraviolet-resistant coatings tend not to extend the lightfastness of dyes. Every test that hand-dyers I know have done with UV-resistant sprays or laundry treatments shows no significant protection at all, and some of these coatings may even increase the sensitivity of dyes to sunlight, probably through by absorbing the light energy from ultraviolet light and passing it on to the dye molecules. I believe that the failure of UV coatings to protect dyes is because the damage is being done by the visible portion of the spectrum, as was described for several dyes in my PhD dissertation. When light strikes a colored molecule, it is the visible portion of the spectrum that is absorbed, converting the energy from the light into energy that is absorbed by the dye molecule. This energy is what ultimately leads to the destruction of the dye molecule.

Most yellow natural dyes suffer from poor lightfastness. For a more lightfast yellow natural dye, use either weld (from the plant Reseda luteola) or quercitron (from the inner bark of the American black oak tree, Quercus velutina). Another traditional yellow natural dye, old fustic (from the tree Morus tinctoria), is less lightfast than quercitron or weld, but it is much more resistant to light than turmeric. Iron buff, obtained by dyeing with the mineral ferrous sulfate, is very light-resistant, but whether it is truly a natural dye is a matter of interpretation. Instructions for dyeing different fibers with each of these dyes, and information about their lightfastness and the lightfastness of other natural dyes, may be found in J. Liles' book, The Art and Craft of Natural Dyeing: Traditional Recipes for Modern Use.

If you need a lightfast yellow dye, I recommend that you consider using a synthetic dye. The lightfastness of synthetic dyes varies considerably. In general, the most light-fast of dyes are the vat dyes, which are chemically related to the natural dye indigo. If you look in the vat dye section of my page showing lightfastness ratings for many dyes, you will see that a number of yellow vat dyes have good lightfastness ratings. C.I. vat yellow 33 has a lightfastness rating of 7, on a scale of 1-8. Vat orange 1 and vat orange 7 both have lightfastness ratings varying from 6 to 7 on that scale. Some reactive dyes are also very good. Reactive yellow 86, which is Procion Yellow MX-8G, also has a lightfastness rating of 6-7, and is much easier to apply to fabric than any vat dye; it is readily available from many sources. Other reactive yellows, and all of the reactive oranges, have lower lightfastness ratings, though they are considerably more lightfast than turmeric.

Do not use cationic dye fixatives, such as Retayne, when lightfastness is an issue. Although these dye fixatives are essential to make the washfastness of direct or all-purpose dyes acceptable, they tend to significantly decrease the lightfastness of most dyes that they are used with.

For more information, see the following pages:
• Lightfastness of dyes
• DNA damage and cell lethality by photodynamically-produced oxygen radicals
• I am dyeing silk fabric with natural dyes like tumeric, coffee etc. How do I fix these dyes with natural substances?
• Turmeric dyes practically everything!

(Please help support this web site. Thank you.)