[LargeFormat] Fungus

[Richard Knoppow]

----- Original Message ----- 
From: "philip lambert" <philip.lambert@ntlworld.com>
To: <largeformat@f32.net>
Sent: Friday, June 13, 2003 2:10 AM
Subject: Re: [LargeFormat] Fungus


> I just bought unseen a wideangle lens and it arrived today
having what
> appears to be a deposit of wool on the outer surface of
the rear glass that
> withstands conventional lens cleaning materials.
> I assume this is fungus. It is quite obvious, more so with
a loupe.
> Does anybody have an effective metod of cleaning this off
and is the glass
> left with a surface mark?
> Does a cleaned off fungus return?
>
> At the moment the lens is enjoying some strong sun on the
window ledge prior
> to be returned to vendor for a refund..
> Philip
>
  That doesn't sound like fungus. Check it and see if it is
actually something on the surface or if the surface is
etched. Some types of fungus exude a substance which
dissolves glass leaving tiny pits or sometimes a spider web
pattern. There is no fix for this. I think there can also be
pitting where moisture is allowed to condense on a lens
surface over a long period of time.
  I've also seen elements where the surface was cracked in a
radial pattern. Both of these were internal surfaces, one an
ancient Dagor copy, the other an old Leica lens. I have no
idea what causes this.
  Fungus can come back if spores are left.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com