[LargeFormat] Silica Packs to avoid the Fungus

[Clive Warren]

At 5:58 pm -0800 7/11/01, Brock Nanson wrote:
>
>  > To make it a little more interesting, I use Q-tips (cotton buds) with the
>>  smallest amount of Ponds Cold Cream and apply with a circular motion using
>>  reasonable pressure to the affected areas.  I have used other lotions in
>>  the past but Ponds seems to be the best. This is followed by an
>application
>>  of pure alcohol to degrease and then a micro-fibre cloth for a final
>polish.
>
>I'm curious to know, would you use this procedure on coated glass?  Do you
>see any consequences to doing this?
>
>Brock

Yep - coated or not it is the same procedure. If an old uncoated lens 
has a fine "bloom" (not fungus but some form of oxidisation) on the 
front element then I leave it as it supposed to act in a similar 
fashion to modern coatings.

The fungus actually eats the coating on lenses and can etch the glass 
underneath.  The consequence of cleaning the fungus when it has been 
in the lens for a while is to leave a patch of uncoated glass. If you 
are lucky the fungus will not have damaged the glass. Depending on 
where this is in the lens it may have an effect on contrast. Modern 
multi-element lenses are designed to work most effectively with their 
coatings intact.  However most large format lenses do not have too 
many separate elements so this is not so much of a potential problem 
as it would be in say a 35mm zoom lens.

Older coated lenses may well have a fairly soft coating so it pays to 
be very careful that you do not inadvertently remove good coating!

Ponds Cold Cream came highly recommended to me by a chap in the US 
who uses it professionally for lens CLAs where there is a fungus 
problem.

Cheers,
        Clive