[rollei_list] Re: OT: Zeiss lens cleaning wipes?
----- Original Message ----- From: <chatanooga@xxxxxxxxx> 
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Friday, May 30, 2008 3:03 AM
Subject: [rollei_list] Re: OT: Zeiss lens cleaning wipes?


Hi Richard
I think you have also recommended isopropyl alcohol as something to add for the final rinse when washing film? Sounds like versatile stuff that I should try. Is it sold as you call it here or is there a product name? 
rgds
Chat
Its sold as isopropyl alcohol or its newer chemical name isopropanol. For cleaning lenses or film it should be 99+%. The impurity is mostly water. If alcohol is left exposed to the air it will absorb moisture until it reaches 91% at which point its at equilibrium. The problem with alcohol that has moisture in it is that as the alcohol evaporates it leaves the moisture behind. You don't want this on lenses and certainly not for film because the moisture will cause streaking. This is Kodak's current recommendation for film cleaning but they warn not to use it on the support side because it will dissolve some film supports. The trick of adding it to the final wash was told me by a Phd chemist I used to have considerable correspondence with some years ago. By adding it to a solution of Photo-Flo a sort of super wetting agent is formed. The Photo-Flo should be used at half strength and the alcohol added at about 30 ml/liter of rinse. In this case you can use ordinary rubbing alcohol, which is usually 70%, because the water doesn't matter. Isopropyl is relatively non-toxic and does not present an environmental hazard, however, it is inflamable, especially at 91% or stronger (used in alcohol lamps), and is rather irritating to the skin. Other cleaning solvents recommended for film and lenses in the past have turned out to be either quite toxic (carbon tetrachloride) or environmentally damaging (1,1,1,trichloroethane). Both of these were used for years because they are effective and non-inflamible. 

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Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 
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