Ask A Scientist Chemistry Archive

(Created prior to 1993)

Question: I need references high school students could access for info about 
bonds (types, process, etc.) between cotton fibers and dyes.  Current 
references do not provide enough detail.
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Are you asking about the kinds of chemical bonds which can occur 
between a dye molecule and a shirt fiber?  Or are you just interested in a 
general sense in how dyes work?  One reference I found is "The Chemistry and 
application of dyes" edited by David R. Waring and Geoffre Hallas (New York, 
Plenum Press, 1990).  Another is "Colour Chemistry" by Reginald L.M. Allen 
(New York, Appleton-Century-Crofts, 1971).  Finally, try "The colour science 
of dyes and pigments" by K. McLauren (Bristol, A.Hilger, 1986).  I spoke with 
my wife (who is a tie-dye expert) a little about dyes.  She tells me that 
fiber-reactive dyes, like the ones she uses, bind to the individual fibers of 
cotton cloth.  The main reason she uses cotton is that the fibers are 
naturally hollow, and dye molecules can form bonds to the fiber from the 
inside and outside of the fiber (resulting in brightly colored fabric).  The 
cotton fabric is prepared before dying by soaking in potash, a powerfully 
basic substance.  I suspect that this "charges up" active sites on the cotton 
fibers, similar to the way that one "charges up" an analytical resin column 
with acid before passing a solution through it to remove unwanted impurities . 
. .  charged with active sites, the dye has many places on the fiber surface 
to form good strong bonds.  Now, if you are using those el cheapo RIT dyes you 
buy at the supermarket, your shirt will probably run.  They are not fiber-
reactive at all, but are merely pigment dyes.  They will look nice at first, 
but every trip through the washer will remove some of the water-soluble dye 
and eventually your cool "Grateful dead" pattern has turned into a brownish-
pink mess.  So, either use fiber-reactive dyes, or do not wash your shirt! 
Topper
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