Gold, silver, stainless steel, pewter, Cocao butter, coconut

[dabateman]

This is a quick UV range series inspired to see if silver goes black into the UVB. It slightly does, but its not dramatic.

 

EM1 full spectrum converted camera with UAT 85mm lens at F11 Using a 302nm Light and a Exoterra 200 UVB 26W light bulb

 

Visible (No filter CWB worked at 2650):

 

303bp10 with U330WB80 improved filter:

 

313bp25 with U330WB80 improved filter:

 

335bp10 with BaaderVenus U filter:

 

Baader Venus U fitler only:

 

Now more dramatic in Monochrom using the KSS100A imager and the stock GM5 on the back, the next two images shot with a single 15W germicidal light.

 

193bp20:

 

253bp25:

 

This series was shot only with single ExoTerra 200 UVB 26W light.

 

303bp10 with 2mm U340:

 

313bp25:

 

335bp10:

 

370bp15:

 

390bp25:

 

405bp10:

 

I only have sterling silver bracelet with is draped over the cocoa butter. Its 92.5% silver, I am not sure if pure silver would look different. I also cleaned it prior to imaging using the baking soda with aluminum boiled trick. Prior to cleaning it was quite black, more noticeable than the images above. So UVB may not be the best way to pull silver out from a bunch, just wait for it to oxide.

[Stefano]

Nice to see these images! It’s been months since I wanted to see this, I wandered how it would have looked like to image it. Probably the problem is that you need a very narrow line/filter to see black silver, like <5 nm. Silver goes black only in a sharp point.

[Andy Perrin]

Yes, this is like the dark water issue except even more severe since the water doesn’t lighten up as much after 976nm.

[dabateman]

It seems fairly tight. If you scroll between the monochrome 303, 313 and 335nm images you can see the difference. But its not shocking.

 

Also disappointing was the coconut and cocoa butter between 193 and 253. I think I am just seeing to 250nm with the imager. Or I can't get enough 185nm line.

I need somthing that is black below 230nm, but not above to really figure out if the 193bp20 filter is working.

 

Also just noticed that the rock my wizard is holding is bright or glowing under UVC, but not in other images. I will have to see if there maybe a known rock that might show the difference I want.

[dabateman]

Ha found it isopropyl alcohol (IPA) has an absorption at 205nm!

 

I also have pure IPA 99% for sensor cleaning. Will have to image various IPA concentrations.

 

Water also seems to absorb hard at 190nm. I didn't know that.

https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_by_water#/media/File%3AAbsorption_spectrum_of_liquid_water.png

 

[Stefano]

Ha found it isopropyl alcohol (IPA) has an absorption at 205nm!

 

I also have pure IPA 99% for sensor cleaning. Will have to image various IPA concentrations.

 

Water also seems to absorb hard at 190nm. I didn't know that.

https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_by_water#/media/File%3AAbsorption_spectrum_of_liquid_water.png

Yes, water is transparent in radio waves, NUV-VIS-NIR, X-Rays and Gamma Rays

[Stefano]

I guess that this sharp absorption peaks are a good way to test filters. Do you have a quartz (silica) diffraction grating or prism to test what you are seeing at 193 nm? You should be able to see only one line apparently. If you see both the 185 nm and 254 nm lines it means that your filters are leaking (this doesn't mean that they are bad, but you are really going deep into UV, to the point where air starts to ionize, and it simply isn't easy to do that).

[dabateman]

Yes, water is transparent in radio waves, NUV-VIS-NIR, X-Rays and Gamma Rays

 

Actually this would indicate that water is not transparent in UVC or higher microwaves. Its also stated that GHz range microwaves are blocked in water. So no surprise there. You should have said opaque instead of transparent.

 

I don't have a quartz grating, too expensive.

 

But first test using quartz cuvettes, one with tap water the other with 99% IPA and I see no obvious darkness. Thus I can conclude that under most of my UVC imaging conditions I am only seeing the 254nm mercury line.

This maybe due to the bulb not outputing enough 185nm or the KSS100A imager that I have can't image that low. Might only be designed for 250nm to 500nm, which may make sense from a chemical and design point of view.

[ulf]

Yes, water is transparent in radio waves

No it isn't, at least not compared to air.

That is on of the problems to overcome when communicating under water.

You cannot use radio between divers.

For communication with submarines they had to use super long-wave radio at about 17.2kHz

That was one of the reasons keeping the Grimeton radio station operational long after it quickly was made obsolete by the Atlantic communication cables.

https://grimeton.org/?lang=en

https://en.wikipedia.org/wiki/Grimeton_Radio_Station

[Stefano]

 

No it isn't, at least not compared to air.

That is on of the problems to overcome when communicating under water.

You cannot use radio between divers.

For communication with submarines they had to use super long-wave radio at about 17.2kHz

That was one of the reasons keeping the Grimeton radio station operational long after it quickly was made obsolete by the Atlantic communication cables.

https://grimeton.org/?lang=en

https://en.wikipedia.org/wiki/Grimeton_Radio_Station

Yes, I meant radio waves with wavelengths longer than 1 m in small thicknesses (not 1 Km). I know that microwaves are a portion of the radio waves, but I like to consider them as separate things sometimes.

[ulf]

Yes, I meant radio waves with wavelengths longer than 1 m in small thicknesses (not 1 Km). I know that microwaves are a portion of the radio waves, but I like to consider them as separate things sometimes.

Well even radio frequencies quite far from micro waves get attenuated rathe fast in water.

Communication between divers is often solved via ultrasound as radio works very bad under water.

[diant]

I only have sterling silver bracelet with is draped over the cocoa butter. Its 92.5% silver, I am not sure if pure silver would look different. I also cleaned it prior to imaging using the baking soda with aluminum boiled trick.

 

David, a sterling silver have not the same electronic levels filling like a pure silver. Electrons' exchange between cooper and silver occurs.

You may obtain a pure enough silver for your experiment from your 92% one by its dissolution in deluted nitric acid and subsequent deposition a pure silver on a solid cooper bar or tube. Something like

.

 

I've done it more that once and obtained so (after pure silver powder was melted by me into a solid piece) a very different silver which knows no darkening, no fogging through a years. These pieces (on photos below) were melted by me more then 10 years ago. They kept openly and handled frequently without any care. As you can see such really pure silver remains its virgin glossy appearance very long, in contrast with a sterling silver.

 

 

I have not any possibility to check will a such pure silver become dark or black in narrow 303nm or 313nm BP. But it should...

[Marco Lagemaat]

It would be nice to take 

three different  wavelength pictures (for example the pictures in the UVC range  and transfer them to a color channel. And make so a false “RGB” from it. Hopefully you see some different “color” to see what reflect or absorbs in your image. 
 

just an idea… came to mind. 

[diant]

Oh, I have no such possibility...

All I can - to shut the pure silver in one bw channel in around 350-400nm range. Now (right now) I am working with Super Takumar 3,5/35mm and for the sake of curiosity to mount on it Hoya U360 2mm with QB39 2mm. The same piece of pure silver looks like this:

 

 

The same curiosity push me to image my hand next moment, with another UV glass before it - Russian UVG-6 (УФС-6) 5mm.

 

 

It is fanny to see how become transparent a total opaque glass :)

[Andy Perrin]

On 10/11/2021 at 4:59 PM, Marco Lagemaat said:

It would be nice to take 

three different  wavelength pictures (for example the pictures in the UVC range  and transfer them to a color channel. And make so a false “RGB” from it. Hopefully you see some different “color” to see what reflect or absorbs in your image. 
 

just an idea… came to mind. 

It’s an old idea here, haha. We call them tricolor images. It has even been done in UVC by dabateman:

https://www.ultravioletphotography.com/content/index.php?/topic/3585-uvc-uvb-uva-monochrom-acorn-series/

 

[JMC]

I'm asking a basic question here, but what's the deal with silver in the UVB then? I've had a hunt around for absorption spectra in the UV for it, and haven't seen anything yet about bulk silver absorption showing a sharp band in the UV. Genuine question - just curious that's all.

 

EDIT - going back 20+ years, one of the guys in my PhD lab was working with plasma treatment of silver with oxygen plasma to produce silver oxide layers. By playing with the settings he could produce silver oxide layers ranging from white to black. I'm not sure if he ever did UV reflection spectra for those, but with hindsight it would have been interesting to look at.

[dabateman]

Jonathan,  Stefano must have been reading wikipedia one day and saw this:

https://en.m.wikipedia.org/wiki/File:Image-Metal-reflectance.png

 

There is a very tight complete loss of reflection for silver at about 310nm. But its hard to capture unless you have calibrated equipment. 

I might have a better chance with my spectrometer as I do have a reflection probe. 

[diant]

Around 320nm is more correct. Bulk Ag (as Au and Cu) has very interesting electronic levels structure with possibility of interband transition. Ag particularly has the possibility of 4d¹⁰ electrons (from completely filled d-subshells) to jump into half-filled s-subshells 5s¹ after absorbing of ~3.8eV energy.
Here the plot from Gemini Telescope Lab on studying different coatings of their mirrors.

(UHV = Ultra-high vacuum)

 

 

 

 

[JMC]

Ah right, ok thanks guys.

[Stefano]

Yes, David is right. I would have replied much sooner but I can’t post from my phone.

[JMC]

Reading this has now got me wondering if I can image the absorption of silver as it changes. I've ordered some pure silver leaf and will try and image it in visible, and then in 10nm intervals in the UV (I've got bandpass filters from 310nm to 390nm) and maybe even at 254nm as well. If anything comes of it I'll post it on here.

[JMC]

Ok, pictures done. I'll create a new post as I'm just looking at silver, but will refer back to this one.