spot on soft focus lens?

[Tim Meisburger]

I have a Dallmeyer soft focus portrait anastigmat I have finally decided to sell to help finance another camera, but as I was taking pictures of it I noticed spots on the rear element. I thought they were spots in the coating, but then I thought maybe they are fungus. I cannot imagine they would affect the image, but I would not want to misrepresent them if I sell the lens. Any experts that can weigh in?

You can only see them if you tilt the lens to get this flare.

102532

[pierre506]

Would not effect the image but price ~

[Mark Sawyer]

Hard to tell from photos... could it be the natural glass bloom? Is the lens late enough to be coated?

[Tim Meisburger]

Yes, the lens is coated (at least the front element and probably the back as well). I believe the lens was made in the late forties or early fifties and so is single coated. In my experience that early coating was relatively fragile.

[Steven Tribe]

I suppose this is the triplet Dallmeyer?

AFAIK everyone used very basic glass (that is, normally very stable) to make triplets, so not susceptible to fungus. It does look a little like the coating fungal attacks I have seen - with hydrofluoric acid etching.
Another posibility is darkroom droplets/condensation attack which could also explain the rim effect.

[Mark Sawyer]

Yes, the early coatings were delicate. I'd go with Steven's thoughts in the post above.

[Tim Meisburger]

It is the Portrait Anastigmat. I don't know if it is a triplet. Steven, you say its not susceptible to fungus but looks a little like fungus etching. Or darkroom droplets? I'm not to familiar with fungus, but have seen it on (relatively) modern 35mm (format) lenses and it was really visible and clear what it was, but this looks like a faintly visible dishwasher spot. Could a drop of something eat the coating like that?

[Steven Tribe]

Yes, this is the rare Dallmeyer version of the Cooke triplet.
There are, unfortunately, micro organisms which can draw energy from the most horrible of chemical compounds. Thus they have been able to live on the surface of the glass, utilised the moisture and dust, and reduced the metal fluorides to acid.
Dried out chalk water from the taps in many areas looks exactly the same.

[Tim Meisburger]

Is there any way to remove it? A base perhaps? (baking soda?)

[cowanw]

Has anybody used CLR (Calcium Lime Rust, a household cleaning product) for dried out chalk water marks? Does CLR dissolve coatings?