View Full Version : viewing emulsion under a microscope

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12-25-2008, 09:04 AM

Is there a way of using an optical microscope to examine grain size, distribution and shape? Do you have any thoughts on magnification and / or microscope type? How would the emulsion sample be prepared?


Bob M.

12-25-2008, 10:10 AM
I've had developed emulsions under a microscope:
That was with a 10x objective, no eyepiece and a home made camera adapter.

I've also tried looking side-on at emulsions under the microscope. I found it helped to swell the emulsion first, otherwise it's all base and a tiny layer of emulsion on top.
The most difficult bit was cutting the edge accurately enough, as I don't have a microtome.

12-25-2008, 10:13 AM
Bob, without wanting to seem snarky--what is the purpose for doing this? I mean, I'm no stranger to purposeless activities myself ( :) ) but what does this achieve?

Best holiday wishes.

12-25-2008, 10:29 AM
Hello Mike, Ben....


A long time ago, I remember seeing an article where the writer made a microtome from a 3/8 - 1/2 inch (10 - 12 mm thereabouts) diameter nut and bolt. He rotated the nut to almost the end of the bolt (before it would normally fall off) and embedded the object in epoxy (or wax, I think) in the open space. Once the material hardened, he rotated the nut onto the bolt in very small increments to expose the embedded material, and sliced off what he needed. I will have to draw a diagram and scan it in later on.


This is a good question, and I don't mind at all.....

The reason I am asking about the microscope is that I believe it would be helpful if you could actually see what kind of grains (size, shape, etc) result from the different emulsion types and formulas that are possible - when you make them in your location. Even if the formulas are followed exactly, there are different factors in play that can change things. Do you have hard or soft water? Other elements in the water? Copper pipes or PVC or cast iron? Is your thermometer / thermostat / heating element calibrated? What are you using for a timer? Addition rates and methods over time? Things like that. I would imagine that it would be very revealing if you could actually see what kind of grains result from a particular emulsion making setup and procedure.

Thanks, and have a great holiday!

Bob M.

12-25-2008, 10:32 AM
Well, duh, it makes perfect sense for an emulsion MAKER. I'm just an emulsion-exposer, so what would I know?


12-25-2008, 10:37 AM

I could see where it might be interesting to see what you come up with after the emulsion is exposed and processed. I guess it depends on how far you want to take it.


12-25-2008, 01:01 PM
Bob, without wanting to seem snarky--what is the purpose for doing this? I mean, I'm no stranger to purposeless activities myself ( :) ) but what does this achieve?

Best holiday wishes.


Sorry to be in a snarky mode, but it's 1PM and the adults haven't opened their presents yet.

The purpose is to have an excuse to buy a [better] microscope ;)

Best holiday wishes to all, and a Merry Christmas to those who need one.


Photo Engineer
12-25-2008, 01:05 PM

A microscope at about 2500X or higher with oil immersion if possible, will help one view layer composition and developed silver grains as well as dye droplets in color film. This will show gross structure for comparisons. We use this primarily for film design analysis. It is rather coarse and low resolution for anything other than this type of work.

For details and emulsion work, you have to use an electron microscope to see grains and you need something on the order of 0.1 - 10 micron scale to do this. The grain must be made into a carbon replica or the like and the gelatin must be removed to prevent obstruction of the image. These have to be done in specialized labs and are pretty pricey. The silver halide grains are outside of the range of a microscope except as featureless dark dots in most microscopic pictures.

Mastering the microtome method for film analysis is a painstaking job for a craftsman. The microtomed section must be mounted flat in order to see the object correctly. I worked on this for hours at a time, but was never really any good at it myself. We had an open lab for this type of work, but I ended up having to submit my work for a pro to do it.

As a side note, the guy who I usually worked with was a nephew of Anton Dvorak the famous composer. He was a resistance fighter during WWII and had some amazing stories to tell. He was a true artist with a microtome and with the microscope.


Jim Noel
12-25-2008, 01:19 PM
PE beat me to the punch.
What you are seeing with an optical microscope is not the grains, but clusters of grain.

12-25-2008, 04:55 PM
Damn...0 for 2. I'm on a streak!! ;)

Thanks PE and everyone for their input. I guess I'll have to wait until an electron microscope comes up for sale on e-bay. (I'm just kidding).

Happy holidays to all,

Bob M.

Removed Account
12-25-2008, 05:24 PM
I guess I'll have to wait until an electron microscope comes up for sale on e-bay.

Hey, if you've got the bucks and can figure out how to use and maintain it, why shortchange yourself? :D (http://cgi.ebay.ca/Hitachi-S-570-Scanning-Electron-Microscope_W0QQitemZ360118319752QQcmdZViewItemQQpt ZLH_DefaultDomain_2?hash=item360118319752&_trksid=p3286.c0.m14&_trkparms=72%3A1215|66%3A2|65%3A12|39%3A1|240%3A13 18)

12-25-2008, 05:34 PM
There are many electron microscopes on ebay! Price ranges from under a thousand dollar to the mid 10s of thousands. I am gonna stick with my optical scopes. I have known people who had full time jobs just preparing samples for and running those things.

Photo Engineer
12-25-2008, 05:51 PM
PE beat me to the punch.
What you are seeing with an optical microscope is not the grains, but clusters of grain.

With an optical microscope, you see a hint of the silver halide grain as translucent dots before development. After development you see black threads, clumps and dots of silver metal.

I forgot to mention that here, sample prep involves gluing the emulsion side of the film to a substrate very firmly before microtoming in order to prevent deformation or destruction of the emulsion layer. And, photmicrographs of raw emulsion are rather rare.

With an electron microscope, you see the crystal as it actually is.

Electron micrographs run from about $150 to 500 each depending on lab service offered and quantity done at one time.

Both types of imaging have been done on emulsions and pubilshed in textbooks, but electron micrographs are the preferred method for raw emulsion and photo micrographs are preferred for film cross sections.


01-04-2009, 08:51 PM
Here are a couple of links to the web pages of two people who built a scanning tunneling microscope, that alleges a ~1 micrometer resolution...for very cheap money.




hmmm...maybe I don't have to spend big bucks on e-bay after all.....

(go to this link to see a 1.25 um x 1.25 um image: http://www.geocities.com/spm_stm/Progress.html)

Bob M.

Photo Engineer
01-04-2009, 09:43 PM

This is not the same thing. See the photo quality images that I posted elsewhere at the 1 micron resolution.


01-04-2009, 10:11 PM

I should have mentioned that my post was meant more for it's novelty value than for any real practical use.


Bob M.

David Foy
01-06-2009, 01:31 PM
Scientific American published instructions for making an electron microscope at home. Martin Gardner's column, I believe. Check the indexes from 30 to 40 years ago. If I remember right, it involved little more than the kind of parts, equipment and glass work they use at neon sign places.

...just can case anyone is getting bored ...

Alan Johnson
01-06-2009, 02:34 PM
My 1950's microscope is OK for making photomicrographs of edge effects and of negatives of resolution charts but grain(clumps) is a bit beyond it. Attachment,IIRC FP4 in Pyrocat HD with a 40x objective was hard to focus and dim.A modern microscope might do better.

Photo Engineer
01-06-2009, 03:08 PM
Well, here are some things to consider when wanting to look at the internal structure of a film:

1. Looking at the raw emulison - use an Electron Microscope or a Scanning Electron Microscope. Sample prep is critical to see the grains, and resolution must be on the order of 1.0 micron or smaller in the case of paper emulsions. Don't forget the words "SAMPLE PREP". These were done in a special lab. I did quite a few, but never ran the instrument.

2. A microdensitometer is used to look at edge effects. I have posted examples here on APUG. I did a lot of these, but never ran the instrument.

3. Grain is measured as RMSG (Root Mean Square). To do this a microdensitometer is used with special software / hardware to derive the grain profile. A sample is scanned across a given step to get the RMS of the deviation in density. I have no examples, but used to do this often. I never ran this instrument.

4. To look at film structure, you need a microtome and a method of laminating the film to another substrate. You cut sandwiches of this and look edge on to see the structure. Silver grains and silver can be seen as tiny dots with no resolution. Usually, the magnifiacation is about 2500x and an oil immersion lens is used. I did a lot of these myself but was never what you would consider an expert.


Alan Johnson
01-06-2009, 04:05 PM
Hardly anyone has a microdensitomer.Ilford have one, Geoffrey Crawley has one,that's all I have been told.
Would a modern microscope be any use at all? The objective would need high magnification,how high?