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wildbillbugman
10-24-2008, 03:29 PM
Hi All,
I am realy reluctant to post this question. It seams silly. But here it is: Do magnetic fields impact emulsion formation. I always use a magnetic stirring barr.I wonder if I would get different results with an overhead mixer.
Sorry about this,
Bill

Vaughn
10-24-2008, 03:54 PM
Don't know why I am answering this -- beyond the fact that I loved the title...I was trying to figure out how His Holiness, the Pope, became a verb;)

But what is there in emulsions that would be affected by magnetism? Iron compounds? I don't believe silver is. Interesting question, tho!

Vaughn

wildbillbugman
10-24-2008, 04:32 PM
Yes Vaughn,
I left out a "p".
I believe that molecules that are not "magnetic" can be affected (temporarily) by a magnetic field. I don't think that MRI exams depend upon iron compounds in the body being examined. Its a temporary re-alighnment of the molecules.
Bill

Photo Engineer
10-24-2008, 04:55 PM
Magnetic fields do not affect emulsions.

Bill, I used a magnetic stirrer to make my emulsion at the workshop.

PE

Kirk Keyes
10-24-2008, 05:30 PM
The property you want to look up is called "diamagnetism", and silver is diamagnetic. Materials that are diamagnetic will reply themselves from a powerful magnetic field. If I remember right, it has to do with the electrons forming "eddies" or their spin being affected by the strong magnetic field, which I think tries to line them all up with the same spin (i.e. up or down). This allows the magnetic field generate a mild replusion by the atom.

It's pretty weak, but in college, we make some metal complex in the lab and then took a vial of the material, suspended it from a wire attached to a 5 place balance. We put the vial into an electromagnet, and weighed the vial. We then turned on the electromagnet, and then the vial was either lighter or heavier - I forget which. We then took the difference in the two weights and then I think tha mass of the metal complex, and then we figured out the diamagnetic constant for that complex.

So while PE says that magnetic fields have not effect on emulsions, we can have it both ways - Silver compounds can be affected by magnetic fields in that they are diamagentic, but their diamagnetism has no effect on emulsions.

Vaughn
10-24-2008, 06:45 PM
Yes Vaughn,
I left out a "p"...Bill

Thankfully it was not an "o"!

Vaughn

wildbillbugman
10-24-2008, 07:26 PM
Thank you, Kirk,
I also have mind-pops like:Was there ever a man named "No-Sir Arafat"?
But thanks for the intelegent reply. I knew there had to be something in the dark,remote corners of my brain that caused me to sudenly think of that question.

Bill

Ray Rogers
10-25-2008, 06:14 AM
Interesting topic.

I once observed a silicon stopper that had an appearent "magnetic" effect in that it could change the reading on an electronic scale I was using to measure chemicals... when brought close to yet w/o touching it!

Also of note, it absorbed the pink dye of the bag I had stored it in...
becomming quite pink (and not only on the surface!) after storage in the dark for more than a year or so.

After the discoloration occurred, it seemed to have lost most of its "magnetic" effect, having only a doubtful to immeasureable effect.

Never hesitate to talk/ask about the mysterious.

I still think it is amazing that the earth is round and yet we dont fall off.

Ray

Kirk Keyes
10-25-2008, 08:40 AM
Ray, I'd suggest it's not mysterious, but static electricity.

It's the bane of people that do a lot of weighing of really dry objects at less than 0.001 g precision. Dry beaker, dry evaporationg dishes, they can drift for some time, especially when the air that day is dry.

Ray Rogers
10-25-2008, 03:22 PM
Ray, I'd suggest it's not mysterious, but static electricity.

It's the bane of people that do a lot of weighing of really dry objects at less than 0.001 g precision. Dry beaker, dry evaporationg dishes, they can drift for some time, especially when the air that day is dry.

Yes of course that is a possible explanation.

But at the time it did not appear so; there was no clingy tissue "magic", and
there was no appearent dissiptation of the effect, being repeatable again day after day, the "charge" being constant over both time and handling.

In any case, I submit the opinion that what is or is not mysterious is in the eye of the beholder and even in the face of appearent scientific understanding, there are somethings that for some people remain amazing and mysterious.

Besides, much "understanding" rarely exceeds what is akin to an illusion;
It seems there is always something held out of our view, off stage so to speak and that is where the mystery resides, in the unconscious and in that twilight between the conscious and the unconscious.

Yes.

Well, I am just curious, I understand that silicone materials tend to collect electrons and become negatively charged... if this was the case what would you expect the scale to do? Increase or decrease?

Other materials are known to release electrons and become positively charged... would you expect them to affect the scale differently?

How do those people you mention that do a lot of weighing of really dry objects at less than 0.001 g precision, handle the problem?

Is the earlier or later indicated weight to be taken as the most "accurate"?

In the case I described, when in direct contact there was not really any additional drift observed, it was rather magnetic like, increasing suddenly and uncontrollably, as distance neared zero, yet being completly reversible when seperated again.

Not having anyone to guide me through the problem, I found my own solution.

I have no doubt that had you been there we would have found a solution; I think it jollyluckygood that if such a problem arose today, your (and many other's) input would be available.

Ray

Photo Engineer
10-25-2008, 03:38 PM
Ray;

A charged object, when moving, generates a magnetic field regardless of charge (+ or -). Therefore either type of charge can affect an electronic balance.

PE

Ray Rogers
10-25-2008, 03:59 PM
Hi All,
I am realy reluctant to post this question. It seams silly. But here it is: Do magnetic fields impact emulsion formation. I always use a magnetic stirring barr.I wonder if I would get different results with an overhead mixer.
Sorry about this,
Bill


It is interesting to keep in mind that some Electromagnetic Waves which have a magnetic field component will not only affect but will actually EXPOSE an emulsion!

I know you had something else in mind when you wrote your question.
but there is still much that is mysterious to many people about common ordinary phenonoma.

Recent discussions in England about the nature and possible roll of magnetic fields in some photographic phenonmena come to mind.

I do not think your question is silly.
Some people have felt that the direction of stirring a significant item to be controlled.

Now that sounds silly, yet they were respected scientists/emulsion researchers whose work was incorporated in many commercial emulsion formulas.

Ray

Photo Engineer
10-25-2008, 04:15 PM
I have heard the same Ray, but only with respect to the direction of flow of the emulsion down a drain or through a pump. It can be important, but only in very rare cases where turbulence causes bubbles or nonuniform mixing.

In other words, the problem with mixing stems from other than magnetic, and other physical considerations enter into this sort of problem.

As for electromagnetic exposure of emulsions, you are generally confined to radiation of some sort, not pure magnetic phenomena. If magnetic fields exposed film in any way, we would have a lot of foggy MRIs.

PE

Kirk Keyes
10-25-2008, 04:55 PM
In any case, I submit the opinion that what is or is not mysterious is in the eye of the beholder and even in the face of appearent scientific understanding, there are somethings that for some people remain amazing and mysterious.

While I hope I don't violate Clarke's First Law here, I'd like to invoke his Third Law:
"Any sufficiently advanced technology is indistinguishable from magic."


It seems there is always something held out of our view, off stage so to speak and that is where the mystery resides, in the unconscious and in that twilight between the conscious and the unconscious.

Or in the case of diamagnetism, it resides in the field that the electrons make as they smear themselves through space as they zip about the nucleus.

Kirk Keyes
10-25-2008, 05:07 PM
Well, I am just curious, I understand that silicone materials tend to collect electrons and become negatively charged... if this was the case what would you expect the scale to do? Increase or decrease?

Well, I can't say the balance will go high or low. I think it all depends on the balance. I just know they wander about and you sit there waiting for a reading to become stable. You're right about the negative charge, but I think as the balance moves about, some internal parts (pans, arms, housing...) will attract or repel each other, and the charge may disappate through the balance, and mess the stability up more. It just keeps changing and you have to sit there and wait...

When weighing things that are even just slightly warmer than the scale/balance which is trying to wiegh them will usually cause the reading to be high, as a convection current from the warm air rising from the object will pull the balance pan upwards with the movement of the air. That's another bane to people that wiegh a lot of things...

Kirk Keyes
10-25-2008, 05:28 PM
How do those people you mention that do a lot of weighing of really dry objects at less than 0.001 g precision, handle the problem?

Is the earlier or later indicated weight to be taken as the most "accurate"?

Ray - the first thing you can do, is sit and wait...

Another thing that I've seen people try is to put those little StaticMaster strips, like on the photo brushes, in the enclosure of the balance. They have polonium-210 in them and they emit alpha particles - positively charged helium nuclei. They postive alpha particles neutralize the negatively charged electrons. I've never really found them to be effective when used with balances, but some people believe they help...

One thing I do is open the door of the balance, and blow in a gentle breath to add some humidity to the air. It doesn't always seem to help, but it seems like it does sometimes...

Another thing to remember, is to try not to induce any static charge on whatever it is you are going to weigh. I once worked with a guy, who before wieghing out chemicals, would shake the bottle to mix the contents. He would then put in his metal spatula and put it in the container, load up a bit of material, and then pull it out. Works fine, on most things. Well, one day, he had some chemical that was really dry, and it would make a charge on it every time he shook the bottle. As he pulled the spatula out the neck of the plastic bottle, the powder would come flying off the spatula and fly all over the benchtop! It was rather funny to watch. He was totally confused as to why it was happening. I suggested that he not shake the bottle, and next time he weighed that chemical out, he didn't have the stuff come flying out. So try not to induce any static into whatever it is you are wieghing.

Oh, and when it's the middle of the winter, and the air is cold and dry, you will probalby have more problems than when it's warm and wet outside.

Finally - always go with the last weight on stuff. You can't trust a reading because it's moving, just wait until it stops, or at least the variance gets low enough that you don't need a more accurate reading.

Joe VanCleave
10-26-2008, 07:21 AM
A bit off-thread, but:

This thread reminded me of a bit of news that was reported last week. Some researchers unearthed an old paper from a (IIRC) Soviet scientist who conjectured that unrolling adhesive tape in vacuum would release X-rays; this conjecture was recently confirmed; the breaking bonds of the tape's adhesive, in vacuum, would build up enough voltage potential to break electron bonds and release X-rays. Sufficient X-rays to fog a dentist's X-ray film, for instance. A whole new field of study has now apparently been started, as on the video I watched they were able to achieve a 10x increase in X-ray flux by merely using a different brand of tape. This promises an entirely new technology for generating X-rays without HV power supplies and such gear. Of course, most new discoveries end up as weapons, so this will be interesting to watch.

Anyway, back on thread ... I have a StaticMaster dusting brush, but it's been maybe 15 years since it was new, so using it is more like a ritual of faith than real science, since the Polonium has long since decayed. Still, it's a nice conversation starter with friends who know next to nothing about photography; it's not just toxic chemicals, but radioactivity, too!

~Joe

Photo Engineer
10-26-2008, 09:41 AM
Joe;

Peeling off tapes releases electric discharges. You can see this when you rip off the end tapes on 35mm or 120 film. It does fog film. Static discharge contains high levels of UV and there may be some X-ray depending on the power of the discharge, but the atmosphere is very opaque to X-ray and so below a certain level, it cannot be seen. In fact, all X-ray sattelites must be in orbit as stellar X-ray emission cannot penetrate to the surface of the earth.

So, peeling tape in a vacuum and releasing X-ray seems logical to me. It may have gone unobserved due to the weak nature of the release and absorption by air. In fact, the UV release may be a visual component. I seem to have read somewhere that they detected weak X-ray emission from lightning bolts as well. IDK for sure, been years ago.

PE