Emulsion: Oh oy, here's a curiosity question...

[peter k.]

OK... doing some test developments on Arista 400 EDU, one 4x5 sheet at a time, in a black plastic 2" ABS 'daylight tank' I made several years ago.

Today, the negative was pinched inside, and the back side of it was pressed against the plastic, and after fix and rinse, I pulled the negative out to find a 'green' stripe down the back center of the negative.
The emulsion side was facing inward, and had developed fine.

I poured some fixer in a paper cup, and re-fixed it, and the green stripe slowly disappeared.
(Yes, I checked, my fixer with a strip of unexposed film, and it came clear in less than a minute, so it wasn't that)
The negative to the eye held up, looks fine in that area, same development as the rest of the negative.
I'll have to wait to I scan it, to be positive, but it looks fine to me as it is.
So, I'm perplexed and curious, ... what is, was this green stripe?

There is no coating on the back side of a negative is there?
It couldn't be the emulsion, as its only on one side, which was facing inward.
Any ideas?

 

[JW PHOTO]

AH layer is not getting washed with developer if it's tight against the tube or tank. Annihilation coating is the problem.

 

[AgX]

-) some films have a coating at their back

-) some of these coatings incorporate AH means

 

[peter k.]

Annihilation coating is the problem.

Me dinks ista putting me on ;-)

Either way.. love the reply..
Would you, or if it is real, someone care to describe what an annihilation coating is?

 

[Dr Croubie]

Would you, or if it is real, someone care to describe what an annihilation coating is?

The annihilation layer is the coating that goes on top of the Antihalation coating. Normally the annihilation coating gets washed off before the antihalation coating. If you wash off both that's good. If you leave a strip of Antihalation but wash off all the annihilation layer you get coloured stripes, in this case green.
If you manage to wash off the antihalation layer and somehow keep the annihilation layer, then the four horsemen of the apocalypse (carrying their Horsemans) jump out of the frame and go on a killing spree again.

 

[peter k.]

By gosh.. thanks for the explanation, and an apology to JW, I thought he was doing an April fool's day joke, a day late, but found out, that I was one today! Ha...

Film is incredible, love it, the more I learn, the deeper it gets.
So hopefully I will not see the four horsemen of the apocalypse, come out of my dark bag, or daylight tank, so may all the Antihalation and annihilation layers wash off in the order received.

 

[JW PHOTO]

Pete,
Sorry, it's my fault for not explaining it a little better. I was pressed for time in writing the reply and had to rush it. JW

 

[David A. Goldfarb]

In case it's not clear--it's called the "anti-halation" backing or layer, not the "annihilation" layer. It prevents light from penetrating the film during exposure and reflecting off the pressure plate back onto the emulsion from the back side, causing halos to appear (i.e., "halation") around the bright areas on the print (dark areas on the neg).

Efke offered two versions of their IR film, for example, one without the anti-halation backing, producing more atmospheric effects.

 

[peter k.]

Hmmm.. Interesting... the "anti-halation" layer in this film, Arista 400 EDU, (Foma) sticks!

Did two more 4x5 today in the little 2" ABS daylight tank I made, and they both stuck.
Must be a sticker or thicker, or something with this layer, as I have not had this problem with any other 4x5 film I have developed in these one shot tanks.