Torch Glass: Soda-lime, tempered, borosilicate and sapphire

skeet2000

Newly Enlightened
Joined
Jan 13, 2020
Messages
5
Hi all,

Need some expert advice!

I require a flat piece of glass about 1mm thick and roughly 70mm x 35mm in size for use in a bicycle light. My primary concern is transparency followed closely by scratch resistance, but also some glass cost is far too expensive. I'm hoping I can find the optimal solution. One concern is if the glass is custom made then there's a larger risk of impurities or lack of correct polishing.

The light hits the glass mostly square on which (I believe) means reflectivity is less of a concern then opaqueness.

For example in quantities of 1,000 I've been quoted $9.80/each for sapphire and $1.42 for 'tempered glass', which I guess is soda-lime. From what I read borosilicate is much more scratch resistant than soda-lime, but I can't find any borosilicate vs tempered data.

Be good to know what is the price-transparency-scratch-resistance optimal glass!

Cheers!

Andrew
 

knucklegary

Flashlight Enthusiast
Joined
Feb 11, 2017
Messages
4,230
Location
NorCal, Central Coast
Have you contacted FlashlightLens dot com ?

Owner Chris custom cuts sizes, and I believe he uses borosilicate

I wouldn't know anywhere else (Asia?) you could source custom made lenses

Good luck!
 

Olumin

Flashlight Enthusiast
Joined
Sep 20, 2020
Messages
1,337
Location
"...that famous Texas part of Hamburg"
Ive never heard about tempered glass being more scratch resistant. Looking it up on the G it sure seems like a lot of sites are regurgitating the same info, but have no sources or offer no any scientific explication. I would think that the hardness of glas is roughly the same no matter whether it's tempered or not (if someone can explain that'd be great). No idea about borosilicate.

Borosilicate glas is good for high temperature applications because of its low thermal expansion coefficient. It wont crack when exposed to sudden changes of temperature. Laboratory glassware & some kitchen glassware is usually made of borosilicate glas. Its not especially tough whatsoever.

Tempered glas is tougher (harder to break through impact) then both float or borosilicate glas. It is also safer because it breaks into many small, less pointy shards which are less likely to cut someone.

In reality you wont notice a few % higher or lower light transmission, its mostly marketing. What I personally would find much more important for a bicycle light is toughness, so the choice would naturally fall on AR coated tampered glass. You can also look into hard coated acrylic, which is of cause even tougher then tempered glas. You wont notice the 2-3% lower transmissivity.
 

skeet2000

Newly Enlightened
Joined
Jan 13, 2020
Messages
5
I'm not after custom lens but custom glass. It's pretty easy to cut sheet glass with water I'm told.

How about AR coated low iron glass? It's difficult to peal back all the marketing names but I believe it's silica based. I also wonder if the AR coating should be on the inside (if on the outside maybe that scratches easily).
 
Last edited:

skeet2000

Newly Enlightened
Joined
Jan 13, 2020
Messages
5
I'm managed to get a quote of $0.99 per 1,000 for super white (aka low iron) glass, CNC edging, single side AR reflection enhancement, chemical toughened.

Seems ok!
 

aznsx

Flashlight Enthusiast
Joined
Apr 24, 2015
Messages
1,722
Location
Phoenix, AZ USA
Borofloat is the material of choice in a lot of my better 'production' flashlights (the only kind of flashlights I buy), and is used in all kinds of less exotic stuff like space telescope optics, etc. - so I think it's good enough for me.

BTW, this site has some interesting data re: such basic material types:
 
Top