Jeff Blyth's New Ag Coating Process

Silverhalide Emulsions / Chemistry.
Colin Kaminski
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Jeff Blyth's New Ag Coating Process

Post by Colin Kaminski »

This is for home made plates with chemicals available to residential addresses from the Internet. This version is only green sensitive but we could do a group buy on the red sensitizer.

http://d-i-yscience.blogspot.co.uk/2016 ... s.html?m=1
Colin Kaminski
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Re: Jeff Blyth's New Ag Coating Process

Post by Colin Kaminski »

I was sent this question and as I have no experience I thought I would post it here:

Hopefully you can help me with a problem im having with Mr. Jeff's method.
I'm trying his DIY method for red lasers. I got everything in the list but
the issue i'm having is that my gelatin solution gets very hard after
adding the 4ml of Glycerol as mentioned in step 2) and no mater how long or
hot the water bath gets, the gelatin solution won't be fluid again.

After reading and re-reading steps 1) and 2) i cant find what the problem
is. It clearly states to add 12Gr of gelatin leaf to 100Ml. of DI water and
to remove the froth with a filter. To that gelatin solution then add 0.5Gr
of Copper Sulfate previously mixed with 3Ml of DI water. I did it. The
gelatin then changes it' yellowish tone to a blue one. I must mention that
the gelatin is still at 50ºC because i don't let it get colder. It's at
this point that i add the 4Ml of Glycerol and no more that 30 seconds after
i do it, it starts to gel pretty fast until it gets hard and cleaning the
bottle is annoying because the gel takes a lot of time to come off (ok, no
more than 5 minutes, but still annoying).

But then at point 9) it makes it look as if the 0.5Gr. of Copper Sulfate in
3Ml of DI water and the 4Ml of Glycerol are a solution in itself, not to be
stirred in the gelatin after the glass has been coated, which kind of makes
sense because it would then get hard on the glass.
Please, any advice as to how to solve this issue?. I'm i doing it wrong
mixing all into the gelatin?.

By the way, does the hardness of the gelatin has anything to do with it?.
I'm using a local brand of gelatin leaf, it's the second hardest they have
apparently. The softest one they have is 120 bloom. I think the one im
using is around 220~240.

Thank you in advance for any help you can give me.

Enrique
dannybee
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Re: Jeff Blyth's New Ag Coating Process

Post by dannybee »

it is my understanding that "Glycerol" is a plasticizer when add to gelatin,this is also used to make jelly plates and is used with the gelatin (art field)
so i would reduce amount
Martin
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Re: Jeff Blyth's New Ag Coating Process

Post by Martin »

dannybee wrote:it is my understanding that "Glycerol" is a plasticizer when add to gelatin,this is also used to make jelly plates and is used with the gelatin (art field)
Right.
dannybee wrote:so i would reduce amount
No, I would not. I understand the glycerol‘s main function here is to reduce (= "de-activate") the copper sulphate, which otherwise would kill most of the photo speed.
dannybee
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Re: Jeff Blyth's New Ag Coating Process

Post by dannybee »

copper sulphate ? thats used in the bleach not the making or sensitizing of the silver plate. please explain how this would be? you can always use a different bleach ... in most old formulas (photography) they use glycerol to harden the gelatin...but their are different ways to go about this
dannybee
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Re: Jeff Blyth's New Ag Coating Process

Post by dannybee »

sorry my bad, I just reread the paper, I see he uses (copper sulphate) I guess as a added metal to hyper sensitized the layer? is this what he's doing?
Martin
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Re: Jeff Blyth's New Ag Coating Process

Post by Martin »

dannybee wrote:... I guess as a added metal to hyper sensitized the layer? is this what he's doing?
No, its main purpose is to make ordinary („culinary“ gelatin usable for AgX making, at least for the diffusion method.
Usually, these gelatins produce heavy fogging and almost instant silver reduction etc.
For AgX making one has to go for highly purified (and expensive) special photo gelatin.

Adding copper sulphate to culinary gelatin has the additional benefit of making it much less prone to fungal attack.
jeff-blyth
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Re: Jeff Blyth's New Ag Coating Process

Post by jeff-blyth »

Hi Guys,
I have only just spotted this post. I would like to answer any queries mails on this DIY process directly and reasonably promptly. So email me @ntlworld.com where I reside under the username jeffinbath.
To answer the point about glycerol, from Enrique (via Colin) I add this as a plasticizer because I found that the contraction of the gelatin when the plate is drying and crosslinking with the chrome alum, is so great that it often [but not always] tears itself off the glass. So the glycerine or glycerol stops that happening due to its ability to stop gelatin contracting just too much. 4% glycerol has never caused any tendency to gel at 50C or even 40C in dozens of trials including some with a gelatin band listed as 240bloom. Enrique’s glycerol appears to behave as if it has got a contaminant in it that is causing crosslinking. Possibly an aldehyde. Aldehydes (particularly gluteraldehyde and formaldehyde are of course powerful gelatin hardeners. Aldehydes can form in glycerol if it is taken to a high temperature (well over 100C). A small number of OH groups in the glycerol can get oxidized to aldehyde as can occur in any alcohol. It only needs a trace of aldeyde to cause this trouble. Please Enrique, try some fresh glycerol or leave it out altogether and just hope that the gelatin does not tear itself off the glass when drying the film.
The Copper sulphate is a very weak oxidant and I am pleased that it manages to stop fogging from my culinary gelatin without DESENSITIZING the final plate which is what oxidants are inclined to do. Photographic higher grade gelatin does not need it.
Jeff
Heferkimbo
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Re: Jeff Blyth's New Ag Coating Process

Post by Heferkimbo »

I just realized that i shouldn't have posted my other question in the "Beginning holography" forum but here. And it was me the one asking the question, sorry for the trouble i caused you Mr. Colin. I got some answers and thanks to that i'm improving little by little and although the learning curve is somewhat steep, i think i'm making some progress...

My first issue was the hard gelatin due the expired gelatin leaf. After that, it was the random white stains (dots) and now im getting very bad fogging in 4 out of 6 plates in my third batch.... but at least i got 2 decent looking ones. Hopefully the next try will result in 100% fogging/white stains free plates.
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