Transparent Aluminum?



...Chuckle.... well, Don, I spoke for when this took place... at LEAST a dozen years, or more, ago. It may well have been 3X the poly price, but I do remember it was just out of the question at the time.... and now. SBT....
Bill
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Gee wizz. I remember the days when glass was standard and they charged double for polycarb... and I'm not that old!
chuck
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Chuck Sherwood wrote:

Have to agree that poly was more at one time... Cutting edge stuff usually is.
Time/Life does pass quickly...Eh, Chuck? It's like a roll of toilet paper... the closer ya get to the end, the faster it goes!! Ya just don't know which is the last "sheet".
Bill
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lenses.
Several points here. If an optician is charging double or triple for glass lenses you should find another optician. The glass does not cost them much more than the plastic if anything.
Also never opt for scratch resistant coating on glass lenses. It is a waste of money.
Myself I do not buy plastic lenses anymore. I killed one set in two weeks and the second set in two days. If I have to wait for glass I will. The last place I went to get glasses (Wal-Mart) wanted to charge me extra for glass I was about ready to go somewhere else when I had the foresight to ask about the safety glasses. In their pricing structure, they actually charged less for the thicker safety lens and less for the much more durable safety frames than they did for the regular kind. When I enquired why, I was met with a very confused look.
I had a friend that was an optician and a lot of the things they do are for the convenience of the optician. As an example the edger they use to trim the lens down to fit the chosen frame is the same for glass as it is for plastic, but if the place only has one machine then they have to farm out the glass lens work to an outside lab. (It is still pretty cheap to do this.) Also with glass lenses they don't get the opportunity to sell you anti-glare and progressive tints or scratch coating.
One thing I always do is I always get silicone nose pads and spring hinges. I have a fairly large pair of glasses with the thicker safety glass lenses and when these are properly adjusted they don't give me any red marks on my nose or slip off my face, even in the hot sun when I am sweating like a pig. The real light weight frames are for me, a stinking joke. They constantly go out of adjustment because they lack the structural integrity needed to stand up to a little abuse.
--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
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there's a very lightweight metal that mine are made of that are bendable. some sort of titanium alloy i think they told me. they're the lightest i've ever had, stay in adjustment (as i have NEVER had to have them realigned, unlike my previous sets of glasses), and i can twist them into a knot and they bend, but spring back to shape. costs more, of course, but after a few head plants skiing, they pay for themselves.
regards, charlie http://glassartists.org/chaniarts
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Nitinol -- nickel titanium alloy, the so-called shape memory alloy. I've got some in my mouth (orthodontics), as a matter of fact.
Through interesting bits of phase change (that I suppose I should read up on), it defies ordinary elastic theory! As an added bonus, I bet you can put your glasses either in the freezer or under dry ice and, for a few moments, bend the hell out of them. Then as they warm up, they spring right back into place! ;-)
Tim
-- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
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Snip

Would an ultrasonic cleaning bath be any good ? I use mine for cleaning crap off models and will have to try it on reading glasses as I now have to use them since my cararact operation. Alan in beautiful Golden Bay, Western Oz, South 32.25.42, East 115.45.44 GMT+8 VK6 YAB ICQ 6581610 to reply, change oz to au in address
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Alan! Yes, the ultrasonic cleaning does a goog job at home in the wife's jewelry cleaner, I haven't the luxury in the field.... several times per day!.... Thx!! Bill
snipped-for-privacy@iinet.net.oz wrote:

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You want scratch resistance and you want it now? Try the close cousin to the armor, aluminum oxide. Used for bar scanner windows. Very scratch resistant, maybe not as good as this new armour, but good.
Someone here was offering samples at one time. A place that grinds lenses for eye glasses could probably make you some lenses. They use diamond wheels for regular glass.
Dan
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Also known as corundum. This is the stuff sapphires and rubies are made of (with different impurities creating the different colors). In fact, there are watch makers that use corundum crystals for their watches (usually marketed as "synthetic sapphire" crystals).
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snipped-for-privacy@sonic.net says...

Corundum is natural crystalline aluminum oxide, Carborundum is a tradename for manmade silicon carbide.
Ned Simmons
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Ahhh... OK. There lies my confusion. I knew with certainty that both are used for abrasives, at least :)
--
Don Bruder - snipped-for-privacy@sonic.net - New Email policy in effect as of Feb. 21, 2004.
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snipped-for-privacy@sonic.net says...

The reason for the confusing name is apparently that the the guy who first synthesized SiC thought at first that he had created a compound of alumina and carbon. He combined the words carbon and corundum to get Carborundum.
http://chem.ch.huji.ac.il/~eugeniik/history/acheson.html
Ned Simmons
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My last (recent ) set of glasses with glass lenses are very abrasion sensitive. The lenses are uncoated. Has the lens glass been getting softer to make the manufacturing easier? It really bugs me that my old glasses were about ten times more scratch resistant than the new ones.
--

Boris Mohar



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Don Bruder wrote:

Isn't Aluminum oxide Sapphire? Don't know what percentage of nitrogen they are talking about, but if I remember right pure Sapphire (straight aluminum and oxygen) are transparent- color is due to various impurities. I know sapphire is used for infrared lenses and windows. I see no reason similar materials cannot be used for lenses, but one must check the dispersion charactoristics to see if result would give too much chromatic aberration.
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Corundum -- Al2O3 Hematite Group - Sapphire is a color type gem that isn't red - ruby is red. Other colors are sapphire - blue( star), black (star), yellow, .... also known as corundum, magnetite, hematite, and spinel.
That is first year Mineralogy class. Useful when trading stones...
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Don Stauffer wrote:

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I'll buy that one, as I already know it's correct.

But not these two, which I know in both cases to be forms of iron, not aluminum. Magnetite, in particular, is definitely ferrous - Under the name of Lodestone, in association with a piece of string to hang it from, or a cork and a bowl of water to float it with/on, it was humanity's first compass needle. Except when used as a coil winding, I've never heard of any form of aluminum exhibiting magnetic properties... As for Hematite, I've heard it described, by several different persons in positions to know, as "crystalized rust" because it's essentially a lump of iron oxides with a handful of impurities.

Eh... Might be, but not sure, and not interested enough to find out.
Perhaps being classed in the "Hematite group" indicates they all have similar crystal structures? They definitely don't have the same molecular structures!

Mayhap someone needs to attend it... :)
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These things were listed rather ambiguously, but I know what was meant: Hematite, corundum, chromium oxide and I think a number of rare earth oxides, all take the same crystal structure, and have similar atomic dimensions so are somewhat replacable by each other.

...
The other interesting aspect of the above-mentioned trio is they form a nice stable crystal structure with divalent metals, known as the spinel structure. The divalent metals include (let's see if I can get them all from memory): magnesium, manganese, iron, nickel, zinc, and in a related vein, lead. (Note that iron appears in both lists because it is di- and tri-valent!) Thus, what you get are 15 combinations of these elements, known as spinels, of the form XO.Y2O3 = XY2O4. For example, the namesake mineral spinel is magnesium aluminate, MgAl2O4. Chromite, the chromium ore, is ferrous chromite (not chromate), FeCr2O4.
A consequence of the dual behavior of iron is magnetite, FeO.Fe2O3 = FeFe2O4 = Fe3O4. Magnetite is very stable: at high temperatures, it can be reduced to ferrous oxide (FeO), but between 300 and 560C, FeO disproportionates to iron (metal) and magnetite! Likewise, it can be oxidized (most easily by weathering at low temperature), but Fe2O3 actually decomposes into Fe3O4 with a release of oxygen at 1451C. Magnetite also has a higher melting point than FeO, slightly higher than the melting point of steel (though you can't observe this directly because any oxide attached to that melting piece of steel will be reduced by the metal, causing the slag to literally drip off the iron, which looks very interesting).
Industrially, chromite refractories such as MgCr2O4, FeCr2O4 and MgAl2O4 are often used to buffer between cheap, acidic, silica-rich firebricks and more expensive, basic dolomite and magnesia bricks. The basic bricks are used because, in addition to being highly refractory (MP > 2400C), they absorb sulfur and phosphorous from the steel contained within. These basic refractories gave rise to the terms "basic oxygen process" and "basic open hearth process", neither of which are mechanically "basic". ;)

That's because they aren't in molecules, they're in crystals. ;o)
Tim
-- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
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I know you are familar with Alnico, an aluminum alloy. It is so different from most aluminum alloys that I usually forget it too.
Dan
Don Bruder wrote:

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Sorry to say - I'll plagiarize and show you a bit closer to the facts.
In Oxides and Hydroxides Hematite Group Corundum- Al2O3 Name: Probably derived from the Sanskrit, Kuruvinda, "ruby"; korundum. Varieties: A very impure material, known as emery, is an intimate mixture of granular corundum, magnetite, hematite and spinel.
So Emery is a variety of Corundum and happens to be the only entry in the book in this reference.
Spinel is MgAL2o4 it has a touch of Magnesium and another oxygen. Can be man made easily. (and is in another group - the Spinel Group.)
Ruby add chromium for some of the Al. Not all. Sometimes the lesser ruby is Fe or Ti or now FeTio3 all together.
Hematite is Fe2O3 Ilmenite is FeTiO3 Geikielite - MgTiO3 Pyophanite - MnTiO3
So as chemical elements - there are not exacts for this or that. Gemstones are mixtures of alloys... And the names are the confusing issue. Different chemical content for the same name simply due to local use, greed, or custom.....
What I slipped up on is truncating to much stuff and left off the 'emery'.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Don Bruder wrote:

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