Denatured alcohols

I am a freelance paper conservator (UK) and I'm in the process of
applying for a license from HMRC in order to purchase Industrial
Denatured Alcohol (IDA), formerly known as Industrial Methylated
Spirit (IMS).  HMRC have however questioned why I cannot just use
Completely Denatured Alcohol (CDA) instead.

CDA usually has purple dye in it which makes it unsuitable for
obvious reasons, however HMRC have advised me that the dye is no
longer legally compulsory in CDA, thus clear CDA is available, so
unless I have any other reason why I can't use it they won't issue
me a license.

I have searched online and found that the ingredients do differ a
little:

    "Purple meths", otherwise known as Completely Denatured Alcohol,
    consists of 90% by volume of ethanol, 9.5% wood naphtha or an
    acceptable substitute, 0.5% crude pyridine, plus mineral naphtha
    (kerosene) and methyl violet dye.

    Industrial Denatured Alcohol consists of 95% ethanol and 5% wood
    naphtha. See more at:

        <URL:http://britishlibrary.typepad.co.uk/collectioncare/2014/01/industrial-denatured-alcohol-unfit-for-use-as-a-beverage.html>

I have also been advised that CDA can contain impurities such as
magnesium, calcium and iron, which can be undesirable within
conservation treatments (iron in particular).  Therefore is it best
to use IDA as it is purer?

In practical terms it also seems quite hard to source non-dyed CDA
in the UK.

Has anyone had any recent experience with trying to obtain a license
for purchasing IDA?  Or perhaps someone has more specific scientific
knowledge and can provide a solid reason why IDA should be used over
CDA?  Any advice would be extremely appreciated.

Jillian Gregory
Paper Conservator


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                  Conservation DistList Instance 28:37
                 Distributed: Friday, February 27, 2015
                       Message Id: cdl-28-37-027
                                  ***