[QuadList] Toluene

[Tim Vitale]

Methylene chloride and benzene are considered carcinogens.  Toluene
has one methyl group and xylene has two methyl groups on a benzine
ring <http://en.wikipedia.org/wiki/Xylene>.  They are close to being
carcinogens, but not labeled as such.  Xylene is slightly less active
as a solvent, but slightly more dangerous to humans, than toluene.  In
their respective MSDS they have low TWA time weighted average,
allowable OSHA exposure, during an 8-hr work day:

Toluene TWA 200 ppm
Xylene TWA 100 ppm

I think this makes xylene worse than toluene.

When were the Ampex recommendation made?  Likely in the 1960s or ,
early 1970s.  Through the mid-1980s these many dangerous solvents were
given a pass, but then it all hit the wall in the mid-1980s.  I don't
know the history of MSDS but they became required starting 1975-82
era.  I Google the MSDS for the chemical and look at the toxicity
section.   

Methylene Chloride MSDS
<http://www.jtbaker.com/msds/englishhtml/M4420.htm>
Benzene MSDS <http://www.sciencelab.com/xMSDS-Benzene-9927339>, sorry
its not the same format, no one with good info had all four.
Xylene MSDS <http://www.jtbaker.com/msds/englishhtml/x2000.htm>
Toluene MSDS <http://www.jtbaker.com/msds/englishhtml/t3913.htm>
Definition of MSDS terms <http://www.ilpi.com/msds/ref/tlv.html> &
<http://www.ilpi.com/msds/ref/pel.html>.

I wouldn't use any alcohol, but anhydrous ethanol is best, unless its
been in the open air for awhile.  With many materials, ethanol and
methanol swell about 60% (EtOH) to 40% (MeOH) of water; often quite
dangerous.  

Methylene chloride is a wonderful solvent, as is DMF dimethylfomamide,
but they are very dangerous to use.  BTW, cross-linked polymers will
swell in the Methylene chloride and DMF, but they won't dissolve.
Rubber is a crosslinked polymer.

Tim Vitale
Paper, Photographs &
Electronic Media Conservator
Digital Imaging & Facsimiles
Film [Still] Migration to Digital Format
Digital Imaging & Facsimiles
Preservation Associates 
1500 Park Avenue 
Suite 123
Emeryville, CA 94608

510-594-8277
510-594-8799 fax 

tjvitale at ix.netcom.com
Albumen Photography Website in 2000
<http://albumen.conservation-us.org>
VideoPreservation Website in 2007
<http://videopreservation.conservation-us.org>


> you didn't say anything about 
> Xylene. Can you compare and contrast with Toluene?
> 
> Also, some Ampex audio equipment users recommend lighter fluid.
> 
> Some comments from the Ampex list:
> 
>  I would be especially careful about using any of the high 
> concentration alcohols for head cleaning, because these 
> alcohols are hygroscopic and absorb water vapor out of the 
> atmosphere.  This does two things, first it rapidly dilutes 
> the alcohol to the point where it won't dissolve the tape 
> binder goop, and secondly, it leaves some water on the iron 
> head laminations -- especially, making use of the low surface 
> tension of alcohol-water solutions, getting down into little 
> crevices in the head stack  which may in time rust them and 
> disturb the precise alignment of the head laminations.  
> Xylene is not the least bit miscible with water and so you 
> don't have this problem with it.
> 
>  Xylene is the best product for the purpose.  It doesn't 
> damage epoxy encapsulations or iron head laminations, and it 
> DOES cut the tape binder goop very well - even when it's gone
sticky.
> 
> I spoke with my rubber vendor the other day, and he suggested 
> ethyl alcohol for routine cleaning of nitrile/buna-N pinch 
> rollers.  It's not that expensive and it is generally available.
> 
> Isopropol, even the 99% pure stuff, WILL eventually damage 
> the plastisizers in your rubber and it WILL make your pinch 
> rollers hard. You can't avoid the chemistry on this. Pure 
> ethyl alcohol (without organic stuff making a stiff drink) is 
> OK on pinch rollers but it's extremely expensive in these 
> parts. At least if you get bored you can make yourself a high 
> test adult drink ROFL.
> 
> I've always used ethyl alcohol.  In liquor stores (Everclear 
> brand) or by special permit in some locations (such as 
> Washington State, where sales of grain alcohol are banned).  
> Non-toxic when used as directed <grin>.
> 
> Ampex head cleaner: 86% of Xylenes (O-,M-,P- isomers) and 14% 
> of Methyl Chloro (1,1,1-Trichloroethane)
> 
>  Tri Chlor  used to be cheap, worked well and did what not 
> too many other solvents could. When  you walked into a dry 
> cleaning store  did you ever wonder why they were always smiling?
> 
>  Xylene is a component of lacquer thinner and it keeps the 
> body shop  workers HAPPY.
> 
>  Methylene Chloride is the King of the solvents. It will 
> dissolve a cross linked  polymer overnight. I used to buy it  
> 40m drums at a time for 60 bucks a drum; now it's around $180 
>  for a five gallon pail.