Author Topic: Colloidal Silver Color Samples  (Read 46010 times)

Offline wgpeters

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Re: Colloidal Silver Color Samples
« Reply #75 on: November 25, 2018, 10:42:32 PM »
You would do better if you just used a copper wire for the cathode.  It will help you keep the voltage higher for a given current.
There is no need for a silver cathode.
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Offline FlyingDutchman

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Re: Colloidal Silver Color Samples
« Reply #76 on: November 29, 2018, 07:05:39 PM »
Yes, I agree I have overcomplicated my setup by using two silver electrodes, there is still a lot of room for improvement. Thanks for the pointers.

I would like to get a little deeper into the color and stability issue. It is an issue few people write about, other than saying their silver colloid is 100% stable, or has been stable over a period of a year... but in all cases it is likely that some change takes place in the colloid, right? I have produced colloids in the 15-20 ppm range over the past 6 months with several different protocols, and I have noticed that some seem totally stable, no visible color change over a 4-5 month period. I always keep a small sample in clear glass and daylight conditions.

Some samples show significant red shift after weeks and months. The 80 ppm colloid produced last week that I mentioned in a previous message also seems to show some red shift.

Red shift is a bit tricky, as I understand, because color can be related to particle size (red shift between 2.2 and 12.5 nm and blue shift above 12.5 nm and again a red shift over 20-30nm). Other research relates red shift to change in particle shape (yellow for spherical particles, green and blue for rods and triangles, etc.), with spherical particles being the smallest (largest surface area). I guess the color change, in any case, is related to increased agglomeration, due to influence of radiation (light, heat), as it happens over time (I don't suppose we could count with a spontaneous particle size reduction).

But what I was wondering about specifically, is about the influence of the amount of reducing and capping agent (I agree that an excess of glucose does not seem to have a bad influence, or even seems to have a positive influence on shelf life), and the time you leave the colloid cooking after cutting off the energy to the electrodes? What would be your explanation about red shift in this short period of time? Lack of capping? Overcooking? Excess agglomeration due to other processes?

Online cfnisbet

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Re: Colloidal Silver Color Samples
« Reply #77 on: November 29, 2018, 07:56:18 PM »
...But what I was wondering about specifically, is about the influence of the amount of reducing and capping agent (I agree that an excess of glucose does not seem to have a bad influence, or even seems to have a positive influence on shelf life), and the time you leave the colloid cooking after cutting off the energy to the electrodes? What would be your explanation about red shift in this short period of time? Lack of capping? Overcooking? Excess agglomeration due to other processes?
I have used the same amount of capping agent and electrolyte on all occasions. When you get something that works, it is a good idea to always be consistent. With reducing agents, I have found that glucose and fructose (particularly fructose) both tend to make the end result slightly turbid or cloudy.

However, Maltodextrin reduces the Colloidal Silver very slightly slower, and always produces a perfect result in my setup. I have never had a failure with Cinnamon-reduced Colloidal Silver, but this is regarded as a bit old-fashioned by most forum members, who tend to prefer gelatine capping/Karo reduction due to enhanced stability in the stomach.

The only thing that can happen after the current is shut off, is further (more complete) reduction. I particularly see this when I make heat-reduced Colloidal Silver.

My advice would be to be as consistent as possible. If you alter anything, only alter one thing at a time. The only instability I have ever seen is Ionic Silver Oxide tends to reduce, badly and variably, over time. Sometimes it remains clear, other times it drops out of solution as very large particles. I seldom make this any more. I would suggest that you may have some form of contamination.

Offline wgpeters

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Re: Colloidal Silver Color Samples
« Reply #78 on: November 30, 2018, 01:58:31 AM »
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Red shift is a bit tricky, as I understand, because color can be related to particle size (red shift between 2.2 and 12.5 nm and blue shift above 12.5 nm and again a red shift over 20-30nm). Other research relates red shift to change in particle shape (yellow for spherical particles, green and blue for rods and triangles, etc.), with spherical particles being the smallest (largest surface area). I guess the color change, in any case, is related to increased agglomeration, due to influence of radiation (light, heat), as it happens over time (I don't suppose we could count with a spontaneous particle size reduction).
Color is caused by the surface plasmon resonance of the particles.  Smaller particles absorb shorter wavelengths of light leaving the complementary color which you see.  There is a complicated mathematical formula for the surface plasmon resonance.  Yes, it depends on particle shape.  Its very difficult to make shapes other than spheres.  A sphere has a single resonance, while a rod will have at least two.  When particles are small enough to absorb wavelengths below 400nm (ultraviolet), then the resultant color is clear.... no color at all.  See: https://www.cgcsforum.org/index.php?topic=1292.0
Colloidal silver tends to be yellow because the particles resonate with blue, leaving green and red which together make yellow.

There are two types of stabilizers.  One is ionic which stabilizes by the electrostatic repulsion between particles.  This type is not very strong, and is pH dependent.  The other kind is steric, and stabilizes by it size... this is what gelatin does.  Citrate is not a very strong stabilizer, compared to gelatin.  This is one area where size matters.  Citrate is a smaller molecule than glucose, so I believe it will be a less effective stabilizer than glucose.  Maltodextrin is a chain of glucose molecules, varying from 3 to 17 times bigger than a glucose molecule which makes it a better stabilizer than glucose, but still not as good as gelatin.

colloidal silver made with karo or glucose is stabilized by gluconic acid which results from reducing the silver particles.  Remember that for one thing to be reduced, another must be oxidized.  Oxidizing glucose to reduce silver results in gluconic acid (C6H12O7) which coats the silver nanoparticle. 

Spontaneous particle size reduction never happens. 
« Last Edit: November 30, 2018, 02:17:23 AM by wgpeters »
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Offline FlyingDutchman

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Re: Colloidal Silver Color Samples
« Reply #79 on: November 30, 2018, 03:01:56 PM »
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There are two types of stabilizers.  One is ionic which stabilizes by the electrostatic repulsion between particles.  This type is not very strong, and is pH dependent.  The other kind is steric, and stabilizes by it size... this is what gelatin does.  Citrate is not a very strong stabilizer, compared to gelatin.  This is one area where size matters.  Citrate is a smaller molecule than glucose, so I believe it will be a less effective stabilizer than glucose.  Maltodextrin is a chain of glucose molecules, varying from 3 to 17 times bigger than a glucose molecule which makes it a better stabilizer than glucose, but still not as good as gelatin.

Interesting details! I have to get my hands on some good animal gelatin to experiment. I have had good results with citrate, but gelatin seems to be the way to go.

Offline FlyingDutchman

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Re: Colloidal Silver Color Samples
« Reply #80 on: November 30, 2018, 03:08:31 PM »
My advice would be to be as consistent as possible. If you alter anything, only alter one thing at a time. The only instability I have ever seen is Ionic Silver Oxide tends to reduce, badly and variably, over time. Sometimes it remains clear, other times it drops out of solution as very large particles. I seldom make this any more. I would suggest that you may have some form of contamination.

Thanks for your comments. I am working toward consistency, as you rightfully suggest, keeping detailed records of all productions, but as I am also interested in experimentation. I tend to vary some of the ingredients and amounts to see what happens. Contamination can be an issue, but I don't believe it is in this case, as the reduction in itself take place normally, and there is no turbidity and no precipitation at all. Other than some red shift, the color and aspect seems to be ok, different from earlier experiments where the color would go away or change to some grayish muddy color.

Offline drewcifer

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Re: Colloidal Silver Color Samples
« Reply #81 on: November 30, 2018, 05:04:54 PM »
Why is 20 ppm the concentration at which we determine the particle size based on the surface plasmon response? I've read numerous articles on this forum which describe this phenomenon and I get that we're seeing the compliment of the blue being absorbed (red + green) and perceiving it as yellow, which is fine. But what is special about "20 ppm" which is the concentration that we use when making inferences regarding particle size. There's something I'm not getting, 20 PPM seems like an arbitrary value.

When we make the more concentrated stuff, what different sort of reasoning are we using to explain the color change? Obviously, it seems to be related to the concentration, but how am I to understand this difference in color change? This color change seems to be completely unrelated to the plasmon response explanation.

Sorry, if I'm belaboring some point that's obvious to others, I just can't wrap my head around it, especially the "why we use 20 ppm as the baseline."
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Offline wgpeters

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Re: Colloidal Silver Color Samples
« Reply #82 on: November 30, 2018, 05:51:58 PM »
We use 20 ppm as a baseline because that is about the limit which can be made without any stabilizers.
Higher ppms simply make the color darker, plus the stabilizers like gelatin alter the color by their lensing effect and the fact that their mass slows down the vibrations of the surface electrons.

20 ppm is also the strength most people start out making, and thus know what it should look like.
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Online cfnisbet

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Re: Colloidal Silver Color Samples
« Reply #83 on: December 01, 2018, 11:38:05 AM »
...
20 ppm is also the strength most people start out making, and thus know what it should look like.
Until one can replicate the easiest version, there is no point in trying anything more adventurous. I well remember my first efforts at making what I thought was Colloidal Silver, but which was in fact Ionic Silver Oxide. I had no idea what I was actually making, or what the strength was.

I thank Kephra for rectifying my knowledge in both respects.

Offline FlyingDutchman

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Re: Colloidal Silver Color Samples
« Reply #84 on: December 21, 2018, 01:00:26 PM »
Why is 20 ppm the concentration at which we determine the particle size based on the surface plasmon response? I've read numerous articles on this forum which describe this phenomenon and I get that we're seeing the compliment of the blue being absorbed (red + green) and perceiving it as yellow, which is fine. But what is special about "20 ppm" which is the concentration that we use when making inferences regarding particle size. There's something I'm not getting, 20 PPM seems like an arbitrary value.

When we make the more concentrated stuff, what different sort of reasoning are we using to explain the color change? Obviously, it seems to be related to the concentration, but how am I to understand this difference in color change? This color change seems to be completely unrelated to the plasmon response explanation.

I have been struggling with the color issue, too. What may be interesting is to look into the lab analysis method called photo espectography UV-VIS (visual and UV range). This is an optical method used to analyze colloids, and the graphs produced will tell you two things right away: the most absorbed range(s) of wavelengths and the absorption rate. Absorbed wavelength translates to color perceived, and higher absorption rates indicate higher ppm and darker tints. This lab test is available at most university labs (here in Brazil) at a low cost, and it is something that is in my planning.

Offline FlyingDutchman

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Re: Colloidal Silver Color Samples
« Reply #85 on: December 21, 2018, 01:09:03 PM »
Yes, gelatin makes the color darker.

Several people in Brazil market heat reduced (close to boiling point, constant current control at 5 mA) nano silver (no electrolyte, no reduction agent) as "the true golden silver colloid". I have asked and they claim it is stable over time. What I noted in videos and pictures is that the colloid gets the typical amber color, and after 1 hour cooking it should be around 20 ppm. I haven't found any comments on this process, though you may have addressed this in another post, but I was wondering how heat reduced and heat + glucose reduced compare, and why the 20 ppm heat reduced colloid does not have the yellow color that we would expect from a 20 ppm silver reduced with glucose?

Offline wgpeters

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Re: Colloidal Silver Color Samples
« Reply #86 on: December 21, 2018, 01:16:49 PM »
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but I was wondering how heat reduced and heat + glucose reduced compare, and why the 20 ppm heat reduced colloid does not have the yellow color that we would expect from a 20 ppm silver reduced with glucose?

Silver won't fully reduce with heat only.  The reason is that the actual reducing is done by the hydrogen gas which evolves from the cathode during electrolysis.  The problem is, that some of the hydrogen is lost from the water, so there is insufficient hydrogen to reduce all of the silver with some ionic silver remaining.  Glucose provides complete reduction.
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Offline FlyingDutchman

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Re: Colloidal Silver Color Samples
« Reply #87 on: December 22, 2018, 12:26:22 PM »
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but I was wondering how heat reduced and heat + glucose reduced compare, and why the 20 ppm heat reduced colloid does not have the yellow color that we would expect from a 20 ppm silver reduced with glucose?

Silver won't fully reduce with heat only.  The reason is that the actual reducing is done by the hydrogen gas which evolves from the cathode during electrolysis.  The problem is, that some of the hydrogen is lost from the water, so there is insufficient hydrogen to reduce all of the silver with some ionic silver remaining.  Glucose provides complete reduction.

Thanks for the explanation, I had suspected that the electrolysis of the water was a determining factor, and I would also be worried about other by-products. I suppose I will be able to find those in the many reaction formulas you have provided, I will do some more study, as their reaction is always that they don't want, or don't need to add any chemicals to the process.

Offline wgpeters

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Re: Colloidal Silver Color Samples
« Reply #88 on: December 23, 2018, 06:00:28 PM »
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as their reaction is always that they don't want, or don't need to add any chemicals to the process.
Thats a silly concern.  Glucose, maltodextrin etc are all just foods, and they make a superior product.
To worry about them as contaminants is especially silly since the colloidal silver will be totally contaminated by saliva, stomach acid, enzymes, etc, as soon as it is ingested.
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Offline FlyingDutchman

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Re: Colloidal Silver Color Samples
« Reply #89 on: December 25, 2018, 09:20:33 PM »
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as their reaction is always that they don't want, or don't need to add any chemicals to the process.
Thats a silly concern.  Glucose, maltodextrin etc are all just foods, and they make a superior product.
To worry about them as contaminants is especially silly since the colloidal silver will be totally contaminated by saliva, stomach acid, enzymes, etc, as soon as it is ingested.

Totally agreed, but so far I haven't been able to convince them of the contrary...