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Grade 5 emulsion for enlarging paper

Just another suggestion to make a higher grade paper, what about increasing the silver content per surface unit?

In a MG ilford paper the higher grade is obtained by activating or not an emulsion component, when more silver crystals per surface unit are "active" contrast rises. I using green light a share of the silver is not active, like if it was not there. With blue light more silver per surface unit is sensitive, adding density from all (3, in fact) components.
 

I don't think that's really how it works - MG emulsions are heavily ballasted to avoid crosstalk - if they weren't, you wouldn't get the extremes of scale - and much like the blending of film emulsions, the design aim is to avoid anomalous behaviour at the emulsion changeover points. You can add more silver (up to a point) but there will be a point beyond which you cannot utilise/ sensitise it in a particular crystal growth structure & it becomes 'dead' grain sitting there - https://www.photrio.com/forum/threa...-emulsion-or-why-silver-rich-is-a-myth.26585/
 
Perhaps this is not the same concept than the one explained by Mowrey...

Let me reformulate what I point:

In ilford papers there are 3 component emulsions in a single layer, when illuminating with green light one component emulsion is not exposed, a second component is only partially sensitive to green, so in fact with filter 00 paper works as if it had less silver.

Let's supose that we coat a paper with our emulsion, when dryed we coat it again a second time with an additional second emulsion layer. Lets supose that the upper layer allows to pass enough light to reach the layer under. We would add the density of the upper and second layers.... increasing contrast...
 
di de said:
Hello everybody here
I'm back to emulsion making !

I would like to obtain a high contrast emulsion for enlarging paper (so bromide I presume), an equivalent of grade 4 or 5.

Is it simply possible ? Which way(s) should I explore ?

Thanks
Click to expand...
If you routinely need to print on Grade 4 or 5 then I would suggest you work on negative development, NOT necessarily the paper grade. L
 
Getting high contrast with Cl/Br is often difficult.

Use of Sulfur sensitization increases contrast, and use of Iodide and Phenyl Mercapto Tetrazole all work well. I have gotten grade 4+ with pure Chloride, but it is very much more difficult with Br present.

As for the dual run, this will be a big help as it makes a more monodisperse emulsion with higher contrast.

PE
 
Photo Engineer said:
Getting high contrast with Cl/Br is often difficult.
Click to expand...

PE, I'd make next questions, I've next doubts:

> With same emulsion, if we coat a layer that's x2 thicker then... would we have x2 the contrast, suposing that paper emulsion is well transparent ? this would not be an "industrial" solution because we use x2 the silver... but perhaps it may allow to adjust contrast in a DIY workflow, if a 30% thicker coat sports a 30% higher CI.

> To play with basic Variable Contrast emulsions, may we mix an Erythrosine ortho emulsion with a color blind emulsion ?
if the Erythrosine sensitized component is well washed it should keep its sensitization and the color blind component would not take ortho sensitization... Or better making two layers ? (I realize that at least a third component is necessary to get linear H-D response for a wide grade range.)

Thanks in advance.
 

You might want to read Ron's system engineering posts to get an idea of the way you would use multiple emulsions, balancing the silver content etc to get useful scale - multigrade paper is not wildly different, other than instead of uniformly sensitising the whole emulsion, you would sensitise each discrete emulsion of the three, ballasting the dyes in each to prevent dye migration/ crosstalk.

The posts are here: https://www.photrio.com/forum/threads/photo-system-engineering-ii-b-w-negative-films.35278/ and https://www.photrio.com/forum/threads/photo-system-engineering-iii-b-w-film-2.35520/ - they also explain the problems of multilayer coatings.
 
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If you coat at 5 mil, going to 7 mil may give you 1/2 - 1 grade depending on emulsion and the concentration.

PE
 
If you don't 100% need to make your own, FOMA liquid emulsion is about grade 3.5 in my experience and that could likely be adjusted a bit, possibly made harder by some heating/cooling cycles? It's a quality product. I've got a bottle that expired 5 years ago that's still looking great (stored in the fridge).
 
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