Name: Helen

Message: Dear Paula,
   I adore your website. I am planning on dying a vintage silk kimono a fluorescent color. Do you recommend that I use Remazol Fluorescent Yellow or Rhodamine B? The lightfastness/durability/simplicity of the dye is more important to me than the color shade.

From the Remazol data sheet [PDF] it seems that the Fluorescent Yellow has a lightfastness of 3-4. The Rhodamine has a lightfastness of 2-3 (from your lightfastness page). Can I compare these values directly even though the dyes are different? 

Hi, Helen. I'm glad you're enjoying the website. 

A friend sent me a sample of that Remazol fluorescent yellow, but I have not used it yet. It's a very exciting idea, because as a true fiber reactive it is far, far more washfast than an acid or basic dye, and can be used on a wider range of fibers. I am happy to see the Dystar page whose link you included, as it contains some information I had not seen before.

I don't know if the numbers for the lightfastness of different dyes are 100% comparable, since the tests were presumably done by different labs, but they are the best we have. I think that the tests used are likely to be the same for lightfastness, regardless of dye type. (This is not true for washfastness, in which acid dyes are tested under much milder conditions than fiber reactive or premetalized dyes: acid dyes are wash-tested at 105°F, Lanaset dyes at 140°F, and Remazol and other fiber reactive dyes at 205°F). 

Rhodamine Red, Colour Index Acid red 52 (also known as Basic Violet 10), is noted for poor lightfastness. I am also more than a little uncomfortable about its toxicity, as it has been found to cause cancer in rats, and I have not seen any evidence demonstrating that it does not do the same in humans. Look at this Rhodamine B MSDS [PDF]: "This material is considered hazardous by the OSHA Hazard Communication Standard....Severely irritating to eyes. Irritating to skin. Toxic by inhalation. Toxic if swallowed....LABORATORY TESTS INDICATE MATERIAL MAY BE CARCINOGENIC." In contrast, Remazol dyes in general have been found to be relatively non-toxic. Remazol Luminous Yellow FL is listed as safe for use on baby clothes in Dystar's information on the Oeko-Tex Standard 100 list. 

Sometimes different sources yield different lightfastness numbers for the same dye. Rhodamine B is sold by many dye retailers; Jacquard Products has kindly made information about their acid dyes available online. The figures they give for washfastness and lightfastness for their 620 Hot Fuchsia are 3-4 for washfastness (in 105°F water, not hot water), and 2-3 for lightfastness, so that's consistent with the numbers I found elsewhere at an earlier date. Pro Chemical & Dye doesn't give numbers, but, in their printed catalog, they note for their Washfast Acid 370, which is the same dye, that it (like their fluorescent yellow Flavine Yellow dye) has poor lightfastness, compared to other dyes in the Washfast Acid dye line.

I'm not sure how much more resistant to light fading the Remazol fluorescent may be in practical terms, but the numbers you found are hopeful. I think it would be best to treat your Remazol-fluorescent-dyed garment with care, protecting it from unnecessary light. I'd advise drying garments dyed with it indoors, rather than on a sunny clothesline, and storing them in the dark.

I like Remazol dyes very much. I have been using them on cotton, with trisodium phosphate or soda ash as fixatives. I've tested them with multi-fiber test ribbons which showed that they tend to work better on silk than on cotton under these conditions. As you probably already know, Remazol dyes can also be used on silk without soda ash or TSP, with or without acid, if you steam-set them. It seems likely to be necessary to use either steaming or the high-pH chemical in order to remove the masking group that protects Remazol dyes from reacting in the bottle. Here's a link to my page on Remazol dyes.

I would love to see the results you get in dyeing your kimono. Please consider joining the Dye Forum on my site.


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