Glass
I was thinking of glass the other day. This is not uncommon for me. I admit to being amazed by it. It may be mankind’s oldest discovery, just after fire but before agriculture.
It’s not hard to imagine primitive man throwing different earths onto her (women were in charge of fire, too import for primitive man.) cooking and campfire. The different elements present in the wood and soil could produce interesting colors. Even now, the campfire is often the evening’s entertainment.
The following morning, the women would carefully probe the ashes looking for hot embers to fan into the morning fire. What do you want to bet they found primitive glass?
I was specifically thinking about glass fibers. I was at a rubber company and they wanted to tell the difference between E, K and U type glass fibers. It did not take much thought to put samples of each into the SEM/EDS and collect spectra.
The results were rather nice. E glass contained calcium, (in addition to silicon). Types K and U did not contain calcium, but different amounts of magnesium and aluminum. It was simple to work up a scheme to identify the glass:
Run SEM/EDS on glass, if Ca is present it is a type E, if not check the Al and Mg ratio. If this ratio is greater than two it is a U type. Less than two, it’s K type.
Of course, this is on untreated glass, no etching, coating or leaching.
I felt pretty good about the whole thing until I remembered not everyone has a SEM/EDS. Besides I was white light microscopist and needed to get back to my roots.
What could be simpler than isotropic material and refractive index. I didn’t even control temperature or use a sodium filter!
A drop of liguid, a few glass fibers, close the condenser down, increase the working distance by focusing up and watch the becke line move..
I soon knew the following:
Type E glass had a refractive index equal to 1.555,
Type K glass had a refractive index equal to 1.526
Type U glass had a refractive index equal to 1.520.
Could I select one refractive index to sort them all?
Sure, mount all the fibers in 1.524 and check the contract and becke line.
Type E will have high contrast and be higher than the mounting media.
Type K will have very low contrast and be higher than the mounting media.
And
Type U will have low contrast and will be lower than the mounting media.
So why, would you be interested in this. I don’t know. It’s just the other day I was discussing Dr. McCrone to some non microscopist and I realized it’s been almost six years since he has passed on. Other than a short note published in the Microscope about Microscopist’s Heaven, reportedly communicated by him, his tremendous output of literature and guidance has been missed.
One of the first experiments I did in his introduction to microscopy classes was to distinguishing three isotropic mineral fragments with one refractive index liquid.
It was nice to revisit those memories.
It’s not hard to imagine primitive man throwing different earths onto her (women were in charge of fire, too import for primitive man.) cooking and campfire. The different elements present in the wood and soil could produce interesting colors. Even now, the campfire is often the evening’s entertainment.
The following morning, the women would carefully probe the ashes looking for hot embers to fan into the morning fire. What do you want to bet they found primitive glass?
I was specifically thinking about glass fibers. I was at a rubber company and they wanted to tell the difference between E, K and U type glass fibers. It did not take much thought to put samples of each into the SEM/EDS and collect spectra.
The results were rather nice. E glass contained calcium, (in addition to silicon). Types K and U did not contain calcium, but different amounts of magnesium and aluminum. It was simple to work up a scheme to identify the glass:
Run SEM/EDS on glass, if Ca is present it is a type E, if not check the Al and Mg ratio. If this ratio is greater than two it is a U type. Less than two, it’s K type.
Of course, this is on untreated glass, no etching, coating or leaching.
I felt pretty good about the whole thing until I remembered not everyone has a SEM/EDS. Besides I was white light microscopist and needed to get back to my roots.
What could be simpler than isotropic material and refractive index. I didn’t even control temperature or use a sodium filter!
A drop of liguid, a few glass fibers, close the condenser down, increase the working distance by focusing up and watch the becke line move..
I soon knew the following:
Type E glass had a refractive index equal to 1.555,
Type K glass had a refractive index equal to 1.526
Type U glass had a refractive index equal to 1.520.
Could I select one refractive index to sort them all?
Sure, mount all the fibers in 1.524 and check the contract and becke line.
Type E will have high contrast and be higher than the mounting media.
Type K will have very low contrast and be higher than the mounting media.
And
Type U will have low contrast and will be lower than the mounting media.
So why, would you be interested in this. I don’t know. It’s just the other day I was discussing Dr. McCrone to some non microscopist and I realized it’s been almost six years since he has passed on. Other than a short note published in the Microscope about Microscopist’s Heaven, reportedly communicated by him, his tremendous output of literature and guidance has been missed.
One of the first experiments I did in his introduction to microscopy classes was to distinguishing three isotropic mineral fragments with one refractive index liquid.
It was nice to revisit those memories.
posted by Searcher12 at 1:21 PM
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