[GBW] evidence about Chloramine-T

[Steven Hales <hales@xxxxxxxxxx>]

Well, I've spent some time trying to find out why Chloramine-T has  
fallen out of favor as a bleaching agent for paper. It is not very  
easy locating actual science on this topic. There are lots of  
articles on chloramine-t and fish, water treatment, health and  
safety, occupational hazards, and so on, but not too much about  
paper. One helpful person suggested I search the CoOL archives at  
http://palimpsest.stanford.edu/search.html. I looked at every article  
there that mentioned Chloramine-T. I was able to find several vague  
warnings like this one, from Leslie M. Kruth's article "A Survey of  
Recent Scientific Research which has Caused a Re-evaluation of  
Commonly Used Practices in Book and Paper Conservation" in The Book  
and Paper Annual, vol. 7, 1988. She writes, "The problem with  
Chloramine-T is that it bonds very strongly to paper fiber and can be  
extremely difficult if not impossible to remove." However, no  
evidence is provided for this claim and no further discussion. The  
most useful thing I could locate is "Micro-Raman Identification of  
Bloom Formed on a Historical Print Artifact" by Vincent Otieno-Alego,  
Jennifer Hodgeman, and Dudley C. Creagh published in The Journal of  
the American Institute for Conservation (vol. 40, no 1, 2001). Here's  
what they say:

"The idea that chloramine-T is safe has since been amended.  
Chloramine compounds are unstable, and the residual chemicals present  
on paper progressively hydrolyze well after the treatment time,  
resulting in the formation of detrimental acidic species such as  
hypochlorous acid and hydrochloric acid. These acids can lead to the  
breakdown of cellulose through acid-catalyzed hydrolysis (Hey 1977).  
Another disadvantage linked with the use of chloramine-T is its  
strong bonding to cellulose, which makes it very difficult to wash it  
off with water alone. Thus, after bleaching with chloramine-T, the  
paper is normally rinsed in dilute acetic acid (to break down any  
residual chloramine-T), then washed with water to remove excess acid  
and any water-soluble precipitates, followed by a rinsing in ethanol  
solution to remove organic-type particulates that are less soluble in  
water (Hey 1977). Finally, the bleached paper is deacidified in  
calcium hydroxide (Ca[OH]2) solution, which on long exposure to air  
would allow the formation of the CaCO3 as observed."

The Hey article that they refer to apparently isn't online and I  
haven't been able to get a copy yet. But it seems to me that there  
are many unanswered questions here.

1. Is the residual acid formation inevitable, or does it only  
occasionally occur? If it is only sometimes, what other factors are  
involved?
2. How much acid is formed? "Can lead to the breakdown of cellulose  
through acid-catalyzed hydrolysis" doesn't tell us what the actual  
probability of risk is. Driving a car can lead to your death, but  
that's useful information only if we're told the probability of death.
3. Several authors note that chloramine-T is a potent fungicide. Is  
the acid risk worse than the risk of leaving mold spores in paper?
4. We're told that chloramine-T forms a strong bond with cellulose  
and is difficult to wash off. How difficult? The authors go on to  
suggest a method involving acetic acid, an ethanol rinse, and calcium  
hydroxide. Is that good method?
5. Is it impossible for a water rinse to remove the chloramine-T?  
Does it depend on how long the paper sits in the water? Suppose it is  
rinsed in successive clean baths. Will that do the trick? We're not  
told.
6. There is also a risk/benefit analysis needed that is hard to do  
given the information at hand. There may be less risky bleaching  
techniques, but if they are extremely expensive or difficult then  
that factors in. Flying is safer than driving, but people don't fly  
everywhere because it is too much hassle or too expensive, even  
though our lives are more important than an old piece of paper.

Anyway, those are the questions that come to mind right away. If  
anyone has other information, or answers to the questions I posed,  
I'd be very interested.

Thanks,
Steve


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