The Chemistry Behind Bleach T-Shirts

white king bleachThe most common bleaches in use today, such as the chlorine-based Clorox and Purex, are aqueous solutions containing 4-6% sodium hypochlorite (NaOCl).  They are formed by dissolving chlorine gas in sodium hydroxide according to the following reaction.

Cl2(g) + 2NaOH (aq) –> NaOCl + NaCl + H2O

The chromophore is the part of a molecule which is responsible for its color.  Examples of chromophores include C=C and C=O (Carbon to Carbon and Carbon to Oxygen) bonds.  The chromophore of a dye molecule causes it to absorb certain wavelengths of light and transmit or reflect other wavelengths of light.  An oxidizing bleach such as Clorox breaks chemical bonds in the chromophore so that it can no longer absorb light (a dark t-shirt is absorbing instead of reflecting most light, whereas a light area reflects more light).

When the objective is to bleach a dark object white, problems often arise.  Typically, the new color is orange, not white.  This has happened to me – one day, I was at work and spilled some bleach on my black shorts.  They ended up with orange spots all over them and I had to buy some new shorts.  It may be possible for one to bleach a black object white if he is patient and allows the chromophore-busting reaction to proceed for an extended period of time (considerably longer than 15 minutes; it may take up to one day as the process requires multiples bleach/rinse cycles).  Therefore, I would recommend trying the following procedure to dye a white tiger paw onto a dark-colored shirt (or check out this article to see how it was bleached in orange).

Procedure for bleaching a dark-colored shirt:

1. Bring all supplies to well-ventilated area.  Do not mix with a product that contains ammonia (such as Mr. Clean), as this will lead to the formation of toxic gases.  Wear plastic gloves while handling the bleach.

2. Fully cover the desired area with bleach.  Allow it to sit in a well-ventilated area for two hours.

3. Rinse the clothing in hot water.

4. Repeat Steps 2 and 3 until your black clothing reaches an acceptable shade of white.

5. Wash the shirt thoroughly to make sure that all bleach is removed; this will prevent it from eating away at the cloth.

orange shirt

DR 0’s procedure not followed with this orange shirt!

In an upcoming post Dr. 0 Rankine will detail the results of his own personal test of this procedure.  Needless to say, he is ready and rarin’ to bust up some chromophores!!

Please welcome JCOPRO’s newest contributor, DR 0 Rankine, or Dr Zero for short.  Dr. Zero does actually have his doctorate in Chemical Engineering, not just an undergrad degree like Dolph Lundgren.  Dr. Zero is apparently allowed to wear shorts to work, so he would be the envy of many in industry.  As with all other posts, use your own judgement if attempting anything here

-Jeremy

  1. I teach science. The next topic is on bleach. I will get my class to read this articele. Brilliant

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