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Commonly stocked dyes that work with cotton

  1. May 18, 2014 #1
    We had a few boxes of lab coats recently donated, and I was thinking of tie-dyeing some for fun. Instead of getting a commercial kit, I wanted to use substances we already had in stock.

    I have plenty of sodium carbonate and off the top of my head Congo Red. There is a huge selection of other pigments and dyes that I have never really used. I am fairly sure we have nearly everything on this list:

    http://en.wikipedia.org/wiki/List_of_dyes

    Which of these will work with cellulose? I am assuming I need to find dyes with chlorine in their structure, like crystal violet or methylene blue. Is this a gross over-simplification?
     
  2. jcsd
  3. May 18, 2014 #2
    Is this a gross oversimplification? YES.
    Its almost certain that the coats are treated. A priori you can't know what conditions were used.
    Generally (and I wonder if this isn't already laid out in wikipedia, but you didn't bother to look...) the dying (or is it dyeing?) process is: Treat cotton (to increase dye absorption ), expose to dye, make dye insoluble in situ, revert cotton, rinse excess. This is can be accomplished by changing pH or by use of a selected counter ion. You want a dye that is very insoluble at both physiological pHs as well as in a washing machine, but is soluble under conditions used in the dye process. Obviously, the process shouldn't destroy (much of) the structure of the cellulose. I'm sure the easily available patent literature lists scores of dyes along with their processing requirements (but I'm too lazy to do the work for you). Please note that your idea of "fun" is profoundly environmentally UNfriendly, not to be a spoil sport or anything.
     
  4. May 18, 2014 #3
    Well, here is the dyeing process I had known about already:
    1. soak cloth in sodium carbonate to increase pH.
    2. Twist into pattern.
    3. Apply dye. This forms HCl (takes an H from the cellulose hydroxyl groups and a Cl from the dye) now the two are oppositely charged and attract, forming a CO covalent bond (the reaction takes overnight to complete). This is why I thought I should be on the lookout for dye molecules with Cl in their structure.

    I also thought this was fairly commonplace in Chemistry departments and that someone with experience could help me out, rather than researching every stain/dye/pigment in our stock individually on my own (because there are a great number of them...).
     
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