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Photo Engineer
06-22-2008, 06:23 PM
I was minding my own business when the doorbell rang and there was this kindly old gentleman with a pushcart on the porch. He asked me if I needed any knives sharpened or umbrellas fixed, and I didn't but I did ask him if he could do electron micrographs.

Lo and behold, he whipped an EM out of his pushcart and said let me at it, so I did.

Here is the result. It is a PM of my SRAD camera speed emulsion, mentioned elsewhere. It is a variant that I'm developing for high speed fine grain applications.

As you see, it is about a 1 micron grain, rather monodisperse and consists of what I would describe as "rounded octahedra". It is just what I wanted to make and now I know exactly where I am and where I have been. I also know where to go next.

So thanks to this kindly guy for doing it for me. He got away before I could get him to do more, but hopefully he will be back someday. :D

My wife said that this looks like a convention of marshmallows.

PE

rob champagne
06-22-2008, 06:36 PM
octahedra?

fschifano
06-22-2008, 07:02 PM
Very cool Ron. Kudos.

Photo Engineer
06-22-2008, 07:13 PM
octahedra?

As in octagonal?

http://www.google.com/search?hl=en&q=octahedron

PE

rob champagne
06-22-2008, 08:35 PM
Must be me then because I can see 6 angles round the edge which gives six faces and what looks like a top face which gives 7 faces on the visible side and assuming that is mirrored on the non visible side, then that would give 14 faces. An Octahedron only has 8 faces.
On the other hand you may just be having another senior moment.

Nice pic though...

Photo Engineer
06-22-2008, 09:14 PM
Rob;

Try this and see if it fits: http://en.wikipedia.org/wiki/Truncated_octahedron This as 14 faces.

Nothing is perfect. :(

PE

rob champagne
06-22-2008, 09:23 PM
Thats better...

rmazzullo
06-22-2008, 10:21 PM
PE,

This is very interesting. We can use photos like these as an example of what we could expect when building our emulsions.

Thanks,

Bob M.

CRhymer
06-22-2008, 10:21 PM
Nicely done.

Cheers,
Clarence

Michel Hardy-Vallée
06-22-2008, 10:23 PM
Yes, but was the EM also made on film? ;)

rob champagne
06-22-2008, 11:29 PM
Thats better...

Perhaps not on reflection...

Kirk Keyes
06-22-2008, 11:48 PM
Nice!

Kirk

keithwms
06-22-2008, 11:53 PM
Ron, those are micromushrooms. I think you need to add antifungal ointment to your emulsion.

Frank Szabo
06-23-2008, 12:11 AM
Dip, brush-on or spray-on?

Photo Engineer
06-23-2008, 08:20 AM
The data was in a .jpg file when I got it. The old way was on film, but I guess they do it electronically now days.

The emulsion itself was raw out of the can stuff, never coated. That gives the most reliable data. The sample preparation process is long and tedious to insure you see the grains clearly.

PE

Michel Hardy-Vallée
06-23-2008, 09:06 AM
I was just thinking how cool a mise en abyme it would be to have an EM photo of film that is printed on film, and then make an EM of that photo in turn, ad infinitum...

Photo Engineer
06-23-2008, 09:32 AM
Perhaps not on reflection...

Well, the 14 sided figure can be looked at in two ways if that is your concern.

If you start with an octahedron or a cube and etch off the corners to be flat, either way you end up with 14 sides. Now, further round off the remaining corners and you get what you see. Continuing the ripening and digestion will eventually result in nearly spherical grains which is also not a bad condition.

PE

David A. Goldfarb
06-23-2008, 09:36 AM
Maybe this would be a good place to talk about what the different crystal shapes are, and what the advantages of one over the other would be.

rob champagne
06-23-2008, 09:42 AM
Well, the 14 sided figure can be looked at in two ways if that is your concern.

If you start with an octahedron or a cube and etch off the corners to be flat, either way you end up with 14 sides. Now, further round off the remaining corners and you get what you see. Continuing the ripening and digestion will eventually result in nearly spherical grains which is also not a bad condition.

PE

I think that if you visualise your truncated octahedron from one direction, that it has a lot more corners than the ones in the photo. They are different from what I can see. But you are the researcher so you tell me.

Kirk Keyes
06-23-2008, 10:22 AM
Cutting the corner's off the cubes sounds like a good start, but how does one get the flat T-grains like you see in the SEM images Kodak publishes?

Ron, you say sherical is not bad (which it seems like you've got some tending in that direction as well), but don't we want to maximize the surface area of the grain to it's volume to make the most efficient use of our silver?