Anti-halation coating for homemade silver gelatin plates and sheet film

Ever since I started making my own emulsion I've not been satisfied with with the softened edges around bright objects in the photo as a result of halation caused by internal reflection of the glass/acetate base. I've managed to find more than one book that cites the use of a 0.6% solution of potassium permanganate in gelatin coated before the emulsion. This stops the light from reaching the glass and gives nice crisp negatives.

The way I prepared this solution is I measured out 50ml of water and saved 10ml for the permanganate, added 4g of gelatin to make an 8% gelatin solution and allowed it to swell then heated it to dissolve. I then took the 10ml and added 0.3g of potassium permanganate and lightly heated it to make sure it all dissolved. I then combined the two solutions and it turned orangy-brown to make what I believe is manganese dioxide which is unable to leech through to the emulsion layer as a dye might do. I then dried the coating and poured emulsion on top. This manganese dioxide is destroyed in processing and is not visible when processed.
NB: It is important that everything be dissolved before mixing because i tried swelling the gelatin in the potassium permanganate solution which resulted in the gelatin absorbing a lot of the permanganate and not swelling. resulted in a mess when trying to melt and coat.

I've only tested 1 plate with this but the effect is quite evident if you look in the right places. Ive attached the photos of the tests i did.
This one is the plain emulsion coated on duralar. it has chrome alum which slowed the development and altered the contrast. The halation is most evident on the boarder of the image and where the flowers stick into the air, you can see the lines are a bit fuzzy.


this one is the glass plate coated with the A-H layer, you can see the lines are much cleaner. the contrast is stronger because it had a shorter development time due to no hardener. I didnt add any because I was doing a quick test.

here is the plate with just the A-H layer and the potassium permanganate before adding to the gelatin


I hope you guys find this little experiment helpful!

N.N

Very nice!

Very interesting, thanks for sharing this result! Can you provide any references for the books?

PhotoEngineer recommended using Tartrazine aka FD&C Yellow #5 incorporated directly in the film as an accutance and anti halation dye, although it will cost speed when used this way. Coating a gelatin underlayer as you did here seems like a good idea.

Slightly off topic. But why would people use Cinestill film that removed the anti-halation barrier and live with those light smears?

Alan Edward Klein said:

Slightly off topic. But why would people use Cinestill film that removed the anti-halation barrier and live with those light smears?

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Not everyone wants halation.
I love halation, but not all of the time.
Neat experiment!

Alan Edward Klein said:

Slightly off topic. But why would people use Cinestill film that removed the anti-halation barrier and live with those light smears?

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Mostly convenience and/or politeness.
Convenience: Eliminates the additional step of remjet removal.
Politeness: Does not get labs into trouble by having them process this film in C41, which would foul chemistry, equipment and subsequent films run through them if remjet ends up in the line.

Note that anti-halation is just one of the several functions of a remjet backing.

Perhaps let's go back on-topic now. Like @Andrew O'Neill I find this a very interesting experiment, but I'd also be interested to see more clear examples that demonstrate the difference. It's a little hard to tell just what exactly the contribution of halation was in these specific shots, given other factors like focus and perhaps even possible motion blur.

I'm also quite surprised that the permanganate doesn't somehow wreak havoc on the gelatin layer itself. Carbon printers use a permanganate solution as part of the clearing steps for DAS sensitizer, and it's a well-known problem that applying this solution to a freshly made print before it has dried and hardened fully, it will likely destroy the image in a mass of blisters.

iandvaag said:

Very interesting, thanks for sharing this result! Can you provide any references for the books?

PhotoEngineer recommended using Tartrazine aka FD&C Yellow #5 incorporated directly in the film as an accutance and anti halation dye, although it will cost speed when used this way. Coating a gelatin underlayer as you did here seems like a good idea.

Click to expand...

the book i referenced was Photographic-Emulsions-by-E-J-Wall-1929 page 84 (pdf page 96), just search the book on google and you will find downloadable PDF copies. The recipes in there are far more up to date than other books of the same period.

adding the dye directly to the emulsion might reduce halation but it won't solve the underlying problem which is internal reflections of the glass/plastic. Its worth mentioning that this emulsion already has some tartrazine in it, as well as erythrosine and eosin, tho these are just to enhance the ortho properties rather than act as filters. I am planning to add another layer on top of all this using tartrazine to act as a yellow filter to make the ortho properties dominant over its blue sensitivity. I'll be testing to see whether it makes a difference to add the dye on top of the emulsion vs in the emulsion.

koraks said:

Perhaps let's go back on-topic now. Like @Andrew O'Neill I find this a very interesting experiment, but I'd also be interested to see more clear examples that demonstrate the difference. It's a little hard to tell just what exactly the contribution of halation was in these specific shots, given other factors like focus and perhaps even possible motion blur.

I'm also quite surprised that the permanganate doesn't somehow wreak havoc on the gelatin layer itself. Carbon printers use a permanganate solution as part of the clearing steps for DAS sensitizer, and it's a well-known problem that applying this solution to a freshly made print before it has dried and hardened fully, it will likely destroy the image in a mass of blisters.

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the halation is very subtle but is most noticeable right on the boarder of the negative, its a soft glow that impacts the sharpness.

I'm in the middle of my engineering exams so haven't had much time to test. They are soon over so you will be seeing many more experiments and optimizations coming in the next few weeks.

i was also surprised that the permanganate didn't have much effect on the gelatin, considering that the gelatin appeared to chemically break down the potassium permanganate into manganese dioxide, maybe I haven't tested it enough to notice.
"Carbon printers use a permanganate solution", does this solution have gelatin in it or is it just pure permanganate solution?

thanks for the interest in this little experiment, hope its of some use to you guys

N.N

Nick Carver has an interesting YOuTube on Cinestill and anti halation and also comparing to Portra. The main discussion starts at 18:30.

Sparks n Fire said:

"Carbon printers use a permanganate solution", does this solution have gelatin in it or is it just pure permanganate solution?

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The solution is permanganate, sodium chloride and acetic acid. It's used to treat a carbon transfer print, which is a variable-thickness gelatin matrix with pigment embedded into it. The clearing bath acts to remove the yellow/orange stain left by DAS sensitizer; first the gelatin matrix is soaked briefly in this weak permanganate solution, followed by another brief dip in a bisulfite solution. If this is done as the gelatin matrix is just freshly developed (developing entails rinsing away unhardened gelatin in a warm-water bath) and still wet, the image is usually damaged severely as the permanganate degrades the gelatin; apparently it undoes part of the crosslinking, partly dissolving the gelatin and physically breaking down the image in the process.

Similar problems exist with permanganate silver bleaches used in reversal processing of regular B&W film, where the emulsion tends to blister and/or slide off of the film base.

Alan Edward Klein said:

Nick Carver has an interesting YOuTube on Cinestill and anti halation and also comparing to Portra. The main discussion starts at 18:30.

Click to expand...

That's nice, but it's really pretty far off-topic here. The connection between the halation effects and particularly how they're being handled here in a hand-made emulsion has only very weak relations with a product like Cinestill or the Vision3 films it's derived from.

Hmm, interesting. I just stick a sheet of nonreflective "flocking" paper to the insides of all my plate holders and that seems to eliminate all the halation that I can see, but perhaps my eye is not as discerning and/or I'm just lazy.