HA III yes, but what about the glass?

[Niconical]

Since I've been on the forums I've seen lots of references to the quality of the metal on lights, and the finish. People often list examples like having a light in a pocket with keys for weeks and hardly a mark on the light, or dropping it a few times with only a few nicks in the metal, that sort of thing.

My question is this. How good is the glass? How tough is 'toughened'?

Other than it not looking pretty anymore, I'm not particularly worried about marks on the metal, but I can't see myself carrying one of my lights in a pocket in case the glass gets scratched on a key, zipper, coin or whatever.

Comments?

 

[adamlau]

Through tempering and coating, just like glass used for windows. Or through the use of materials such as sapphire. Threads revolving around scratched glass lenses are far and few in between. There is a reason why.

 

[Niconical]

Thanks for that. I've been worried about keeping the light anywhere but a holster in case I scratched the glass. Now that you mention it, the fact that I couldn't find any "my glass is scratched...." info speaks for itself really.

 

[Jarl]

Since I've been on the forums I've seen lots of references to the quality of the metal on lights, and the finish. People often list examples like having a light in a pocket with keys for weeks and hardly a mark on the light, or dropping it a few times with only a few nicks in the metal, that sort of thing.

My question is this. How good is the glass? How tough is 'toughened'?

Other than it not looking pretty anymore, I'm not particularly worried about marks on the metal, but I can't see myself carrying one of my lights in a pocket in case the glass gets scratched on a key, zipper, coin or whatever.

Comments?

You know the urban rumour to test if a diamond's real? Scratch glass with it. Therefore, not much else can scratch glass, let alone keys, etc.

 

[Gunner12]

If you are really afraid of getting your light scratched, then get a sapphire window, then everything on the outside of the light will be Aluminum Oxide(except the switch of course).

If you commonly carry hard minerals in your pocket along with your light, then I'd be a bit worried about scratching the light's window, but besides that, the glass should be pretty safe.

If the glass is set correctly in the light, it should be pretty impact resistant too.

 

[HKJ]

Your must also remember that the glass is recessed on a flashlight, this will protect the glass in many cases.

 

[xcel730]

If your lens (technically speaking, it's window) is made from sapphire crystal, it's very unlikely to get scratched.

 

[Haz]

a sapphire window is very hard, so it's unlikely to get scratched, however it's possible it may get chipped. Being recessed provides the window with more protection.

 

[orcinus]

You know the urban rumour to test if a diamond's real? Scratch glass with it. Therefore, not much else can scratch glass, let alone keys, etc.

That's not... entirely true. Untempered glass scratches easily. Even hardened mineral glass, as a lot of my cheap watches can attest. Sapphire glass is the only way to go if you want it to be absolutely scratch proof in everyday use.

(while we're on the subject of scratch-testing, and just btw, you can scratch most non-hardened glasses with a tooth - tooth enamel is harder than glass)

 

[Justin Case]

That's not... entirely true. Untempered glass scratches easily. Even hardened mineral glass, as a lot of my cheap watches can attest. Sapphire glass is the only way to go if you want it to be absolutely scratch proof in everyday use.

(while we're on the subject of scratch-testing, and just btw, you can scratch most non-hardened glasses with a tooth - tooth enamel is harder than glass)

Your comment suggests that somehow tempering of glass improves its hardness, which I don't believe is true. What tempering does is induce a surface compressive stress in the glass, which improves the bending strength. Hardness is unchanged.

 

[Justin Case]

Other than it not looking pretty anymore, I'm not particularly worried about marks on the metal, but I can't see myself carrying one of my lights in a pocket in case the glass gets scratched on a key, zipper, coin or whatever.

Comments?

I would not worry. I've carried a SureFire L4 with Pyrex window for many years and the window is pristine. Similarly, I also carry a Gladius as a backup light and its glass window is also pristine. In contrast, I used to carry a SureFire 6P with Lexan window, and it is completely beat up.

 

[Triple A]

I have several L1's that sat in my pocket with other stuff for long periods of time, and I just checked them- not a scratch to be seen. I also strongly agree that a recessed glass window provides a great deal of protection. (Even my NovaTac 120 with "plastic" window is scratch free- I'm guessing because it is set back behind the bezel.)

You can also try what I have been doing recently. Keep a pocket dedicated to knife, (mine all use pocket clips,) and your flashlight. Nothing else goes in. This way there is nothing to scratch it on. (Keys on a caribiner, hung from the belt loop, work great for vacating an otherwise full pocket.) I started doing this not only because I don't like scratching up my lights for any reason other than hard use outside my pockets, but also because I figure they will have a better value if I ever sell / trade them if they are in good shape cosmetically. [So far, however, I haven't been able to bring myself to part with any of my babies:shakehead]

 

[yaesumofo]

I have many many flashlights.
In the early days when ever I modded a Mag light for example I always exchanged the stock front glass(plastic) with a UCL not only are they clear but they do a good job of being scratch resistant.
Whenever I received a light with a lesser piece of plastic or an inferior piece of non coated glass I would install a UCL. NOW many lights come with these as stock.
I can't say that I have ever damaged a piece of glass while carrying or using a flashlight.
No doubt if you really don't want to damage your front glass carry the light in a holster.
I carry using a lanyard 90% of the time at work and I have never damaged a light in edc use. That 1000's of hours of use...

IMHO the most important thing about the front glass is it's ability to transmit light. Sapphire is cool and all but it doesn't transmit light very well in comparison.
Yaesumofo

 

[Yoda4561]

Scratching a recessed glass or pyrex window is difficult to do as long as you aren't out to damage it. Cracks are another matter, they don't happen often but a fall onto a tile/concrete floor can do it. Not that big of a deal though, easy enough on most lights to replace the window. Polycarbonate windows scratch really easily though.

 

[orcinus]

Your comment suggests that somehow tempering of glass improves its hardness, which I don't believe is true. What tempering does is induce a surface compressive stress in the glass, which improves the bending strength. Hardness is unchanged.

I've meant chemical tempering, not heat tempering (though that increases hardness too).
See, for example, here:
http://www.berlinerglas.de/htdocs_en/technical_glass/chemical_strengthening.html

 

[Justin Case]

Your link only discusses hardening via chemical tempering. Thermal tempering does not increase hardness.

See this link for instance:

http://www.aisglass.com/flat_tempered.asp
The color, clarity, chemical composition and light transmission characteristics of glass remain unchanged after heat-treating. Likewise, hardness, specific gravity, expansion coefficient, softening point, thermal conductivity, solar transmittance and stiffness remain unchanged. The only physical properties that change are improved flexural and tensile strength and improved resistance to thermal stresses and thermal shock. Under uniform loading, heat-treated glass is stronger than annealed glass of the same size and thickness. Heat-treating glass does not reduce the deflection of the product for any given load.

 

[orcinus]

Actually, they do say they offer thermally tempered glass with increased scratch resistance too. But regardless, like i wrote, i've originally meant chemically tempered, so the discussion's moot.

 

[Justin Case]

Well, if you are referring to the information on the link you cited, this is what they say:


"Along with chemical strengthening we also offer thermal tempered glass as safety glass with the following characteristics:

• high impact and bending strength
• high bending strength
• high scratch resistance
• enhanced resistance to temperature changes
• breaks into small particles"

It says no such thing that they offer thermal tempering than also increases scratch resistance. It says they offer thermal tempering that has "high scratch resistance". Big difference.

The point may be moot in terms of your clarification that you were talking about chemical tempering, but it isn't moot in that you continue to claim incorrectly that thermal tempering can increase glass hardness.

 

[orcinus]

You're right in claiming "classic" thermal tempering really doesn't do anything useful to the hardness (actually, doesn't do anything to change it at all, contrary to the popular myth saying it actually reduces it).

But there are some funky modern thermal treatments (in high pressure inert atmospheres, temperatures much > than 1000 degress) that increase the hardness. Can't remember where i've read it off-hand, but if i do and/or find the link, i'll post it.

 

[Flashlight Aficionado]

OT Sorry, I just got to know.

orcinus - Dr. McCoy from the episode where he accidentally injects himself and goes insane and then travels in time and meets Edith Keeler?