When to add Erythrosine: A definitive answer?

RogerHyam · Oct 21, 2020

I'm still working with my last emulsion but already planning my next batch. This is obsessive.

I've had two experiences with adding erythrosine to a bromo-iodide emulsion.

I added a couple of drops (1% solution) before 2nd part of ripening and saw little effect but didn't do formal testing. I got this idea from TLF.
I added ten drops before precipitation as suggested by Photo Engineer on this forum a few years back. This was disaster. Lots of fog. No contrast. It turned fixer pink suggesting it hadn't been washed out. I threw batch away.

Since then I've made two successful batches of plain bromo-iodide with no erythrosine (get back on that horse!). But I'd still like some green response.

I'm in a dilemma. For my next batch I could either add very little before precipitation or add more during ripening. Which should I try?

dwross · Oct 21, 2020

Quick question. Did you use a yellow filter with your ortho recipe?

RogerHyam · Oct 21, 2020

dwross said:
Quick question. Did you use a yellow filter with your ortho recipe?

I did try one with the very foggy emulsion but didn't increase the exposure enough and got unusable negs. I didn't try it with the first emulsion. My intension is to use one going forward.

dwross · Oct 21, 2020

If you got a bit of response from the first emulsion, that's probably good news. Here's some information on that: https://www.blurb.com/books/6465389-the-light-farm (p. 72) and if you have time and interest, the chapter on ortho photography starting on p. 54. (The book is free to read in Blurb preview.)

RogerHyam · Oct 21, 2020

Thanks for writing and sharing the book Denise. I've read the ortho section and much of the rest. In your AmBr negative emulsion you add erythrosine before precipitation in a similar way to what I did.

I wonder if I have my erythrosine dilutions wrong. I bought it as powder and made up the dilution myself. Maybe I should just add very little and slowly increase it with each batch till I get fogging.

Also I am use Potassium Bromide rather than AmBr. Might that make a difference to the way Erythrosine behaves?

dwross · Oct 21, 2020

If you have any doubts about the strength of your erythrosin (and even if you didn't), definitely start with a drop and add only one drop at a time more to each subsequent batch of emulsion. At the very worst, you'll have a supply of colorblind plates . By going one drop at a time, you'll be able to sneak up on the fog. Even the batch where you first start seeing it (or, and more likely: a decrease in emulsion speed) should still be usable. That's where you stop and with the next batch, back off one drop.

Pay careful attention to every other aspect of making and using your emulsions, or the tests will be much less useful.

Using KBr won't make a discernable difference.

Good luck and fun!
d

Nodda Duma · Oct 21, 2020

Adding erythro before precip: If it turned the fixer pink, that tells me you didn’t wash properly and/or used far too much.

Keep in mind also the erythrosine allows response up to and including about 620nm, so check your safe lights.

RogerHyam · Oct 21, 2020

I think I'm washing OK: 5 changes of water, 2 minutes each and fine noodles. Most likely I have added too much.

Safelight is a point. I have a mixture of lights. I've tested for Multigrade papers several times and the lights are safe for printing but I note that Ilford recommend a cut off of 580nm so I could be in the danger zone for ortho emulsions.

RogerHyam · Oct 21, 2020

Nodda Duma said:
Keep in mind also the erythrosine allows response up to and including about 620nm, so check your safe lights.

I'm wondering how to do this. Perhaps buying a roll of Ilford Ortho Plus just for testing.

Lachlan Young · Oct 21, 2020

RogerHyam said:
I'm wondering how to do this. Perhaps buying a roll of Ilford Ortho Plus just for testing.

Treat anything other than a Kodak #2 safelight (which is very very dark), Ilford 906 or carefully chosen LED's as potentially unsafe unless you test it - length of exposure to safelight is also important.

dwross · Oct 22, 2020

Low watt red LED lights are very safe and they are inexpensive enough to trade out any non-LED bulbs. Wet emulsion is less sensitive than dry, and most handmade emulsions are very low speed even when dry, so safelight fogging should be at the bottom of the list of potential troublemakers. The real light concerns are light seeping in from outside the darkroom and overestimating how "lightproof" any drying boxes may be.

RogerHyam · Oct 22, 2020

dwross said:
Low watt red LED lights are very safe and they are inexpensive enough to trade out any non-LED bulbs. Wet emulsion is less sensitive than dry, and most handmade emulsions are very low speed even when dry, so safelight fogging should be at the bottom of the list of potential troublemakers. The real light concerns are light seeping in from outside the darkroom and overestimating how "lightproof" any drying boxes may be.

I've always prided myself on having a bright dark room. There are a motley collection of LEDs with generic red perspex in front of them and a Ilford 904 (Dark Brown) with quite a bright compact fluorescent in it directly above the work surface. I've carefully tested them for Multigrade papers but in a situation where I can't test their safeness it may be wise to move to a known spectrum of lighting just to rule out one factor. I'm particularly suspicious of the 904 which passes right into the yellow according to Ilford spec (cuts off at about 570). So I'll try going to just an Ilford 906 (Dark Red) and build back from there once I have lovely ortho plates to do tests with.

Nodda Duma · Oct 22, 2020

I think you found the source of fogging ...

When to add Erythrosine: A definitive answer?

When should I add erythrosine to a bromo-iodide emulsion?

Before precipitation

Before 2nd part of ripening (after reserve gelatin)

RogerHyam

dwross

RogerHyam

dwross

RogerHyam

dwross

Nodda Duma

RogerHyam

RogerHyam

Lachlan Young

dwross

RogerHyam

Nodda Duma

When to add Erythrosine: A definitive answer?

When should I add erythrosine to a bromo-iodide emulsion?

Before precipitation

Before 2nd part of ripening (after reserve gelatin)

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