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ortholux
01-08-2014, 03:50 PM
Dear emulsion makers,

I am a hobby microscopist, trying to learn the art of microphotography (printing a very small image on a microscope slide). After a rather promising start, I am having a lot of difficulties in producing the emulsion. At the moment I am basically wasting time, not getting anywhere. I have a brief description of the process, but it only touches on the subject of very fine grain emulsion making. For this reason I am looking for two papers:

"Small-scale preparation of fine-grain (colloidal) photographic emulsions" H.M. Stationery Off., 1960;

"The preparation of ultra-fine grain photographic emulsions" Journal of Scientific Instruments Volume 31 Number 9, 1954

both by B.H. Crawford.

If anyone has these papers (or one of them), I would greatly appreciate a copy.

Many thanks in advance, and best wishes,
Raymond

RalphLambrecht
01-08-2014, 06:17 PM
pm PE.I'M SURE HE'S YOUR MAN.

MattKing
01-08-2014, 07:45 PM
pm PE.I'M SURE HE'S YOUR MAN.

PE = Photo Engineer.

dwross
01-09-2014, 11:47 AM
Ortholux,

I've had "Small-scale Prep...." on my treasure hunt list for a long time. I've never seen it come up for sale or as an e-book. I suspect an e-book, Google or otherwise, will be the first place it's available. If you find it, I hope you share the source.

In the meantime, there are options for you to try. At the very least you'll learn the nuts and bolts of emulsion making and be ready to take maximum advantage of Crawford's work.

A plain silver (i.e., one made without ammonia) is by its nature very fine-grained. If you look here: http://thelightfarm.com/cgi-bin/htmltutgen.py?content=31Aug2013 , you can see the detail possible in a 0.1 inch square negative. The negative of boats in the harbor was made with a Sputnik camera -- not known for laser-sharp optics. The recipe is here: http://thelightfarm.com/cgi-bin/htmltutgen.py?content=07Sep2013 but be aware that it is part of an educational series. If you start at the beginning of the Light Farm tutorials, you will know how to make an emulsion.

Once you have a handle on the basics, and if you feel you'd like to try for even finer grain, there are a few procedural techniques that will get you there. Try them first one by one, and then in various combinations. This isn't near as much work as it sounds, but the truth is, there isn't a shortcut to proficiency. How do you get to Carnegie Hall?

1) Increase the viscosity of the precipitation gelatin. Do this by taking from the Second Gelatin.
2) Increase the rate of the silver nitrate addition. Pour it in all at once in a slow, steady stream.
3) Shorten the time of the "ripening" after the silver nitrate addition. This is the time the emulsion sits in the waterbath after you've added the silver and before you've added the second gelatin.
4) Substitute potassium or sodium chloride for about a quarter of the ammonium bromide. The combining ratios are close enough that you can substitute one-for-one. Silver chloride, by its nature and as a general rule, is finer grained than silver bromide. It's also slower. Experimentation is your friend.

Best of luck and fun,
d

ortholux
01-09-2014, 02:09 PM
Thanks everyone.

D, I will have a good look at your suggestions. I have already been thinking about starting with the basics first, to get the experience and feel. The equipment is already at my disposal and a new batch of silver nitrate is on the way, so I suppose nothing is keeping me. Thanks!

I will report back if I manage to obtain the papers.

Best,
Raymond

Athiril
03-19-2014, 09:09 PM
Is this what you're looking for?

http://www.freepatentsonline.com/3847617.pdf
The other one you'll need to pay for
http://iopscience.iop.org/0950-7671/31/9/307/pdf/0950-7671_31_9_307.pdf

If you're at an educational institution you might be able to get it from here - http://www.jiscjournalarchives.ac.uk/browse/iop/0950-7671_issues/31_1954.html - or get a subscription (look under issue 9 btw)


However, here is a 2012 paper "Improved silver halide crystals for photographic emulsion"
http://article.sciencepublishinggroup.com/pdf/10.11648.j.am.20120101.13.pdf


Some other interesting ones

https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US6673529.pdf

https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US5541051.pdf

Hologram
03-20-2014, 03:27 AM
I am a hobby microscopist, trying to learn the art of microphotography (printing a very small image on a microscope slide).

Generally speaking, you might take a look into holographic/Lippmann emulsions also. When it comes to image resolution they're certainly good enough for "micro photography"...

By the way, I've got a copy of Crawford 1960.
He gives two different recipes:

Flowing emulsion

High concentration of silver, suitable for very thin coating for fine graticules:
gelatin, 4g in 80ml of water
potassium bromide, 3g in 10ml aqueous solution
chrome alum, 2ml of 1 per cent aqueous solution
pinaflavol, 6ml of 0.5 per cent alcoholic solution.

Casting emulsion

Low concentration of silver, suitable for thick coatings for Lippmann reflection filters of high resolving power:
gelatin, 12g in 80ml water
potassium bromide, 0,281g in 10ml aqueous solution
silver nitrate, 0.375g in 10ml aqueous solution
chrome alum, 3ml of 2 per cent aqueous solution
pinaflavol (or other sensitizer), 3ml of 0.1 per cent alcoholic solution."

Crawford used a kind of double-jet technique by means of two syringes.

ortholux
03-21-2014, 04:38 PM
Thanks, Athiril and Hologram! Much appreciated.

Yes, I have been looking at hologram emulsion making. I actually tried the diffusion method per Jeff Blyth, as well as an 'improved version' of that method, but I was unable to produce a presentable image. Getting a bit disillusioned, I decided to turn to wet collodion. After all this was the method used by the founding father of microphotography (John Benjamin Dancer). At this point I am practising the technique; not yet on a microscopic scale but that is soon to follow because my first attempts are beyond expectation.

But at some point I will want to try gelatin emulsions again. I guess I'm a bit too stubborn to just give up...

Hologram, I will be sending you a private message.

Thanks again,
Raymond

Jim Taylor
03-21-2014, 05:38 PM
Ortholux, PM me and I'll send you a copy of "the preparation of ultra-fine grain photographic emulsions."

Hologram
03-22-2014, 05:28 AM
Thanks, Athiril and Hologram! Much appreciated.

Yes, I have been looking at hologram emulsion making. I actually tried the diffusion method per Jeff Blyth, as well as an 'improved version' of that method, but I was unable to produce a presentable image. Getting a bit disillusioned, I decided to turn to wet collodion.

Since you referred to Blyth's diffusion method, maybe you might combine it with wet collodion. I believe to have not seen mentioned (???) the use of lithium bromide in connection with wet collodion. Since lithium bromide is highly soluble in ethanol, methanol etc., it might be easy to get it into collodion.
I wondered about spectral sensitization. What's the wavelength range you're aiming at?

ortholux
03-22-2014, 04:35 PM
I actually tried a slight modification of Blyth's original method; this one used Potassium bromide in stead of lithium bromide. With potassium bromide, all the substances used were the same as in Groom's article on microphotography (Quekett Journal of Microscopy), which is why I thought it might be worth looking into. I do not have Pinaflavol (the sensitizer Groom used), so it would have made a colour blind emulsion. I have no experience with hologram making; I just thought to 'borrow' the emulsion making technique since both areas need ultra fine grain emulsions.
I am sure there is a lot of room for experimentation; at this point though I am just trying to learn the basics. For the time being I think I better stick to traditional collodion formulas...

Cheers,
Raymond