Thread: Melting Glass with a Laser

Hi! I was recently reading about how a shard of the glass obsidian can have an ultra sharp edge only a few nanometers wide. I was wondering if it would be possible to produce small obsidian blades using a laser or some other machinery.
My primary question is this: seen as obsidian is an amorphous substance that gets softer as it is heated until it begins to melt (at extremely high temperatures) could an ultra sharp edge be produced by heating the edge of a piece of obsidian (perhaps with a laser) that is held at a 45 degree angle? In other words would gravity 'pull' the heated glass lightly until an ultra sharp edge was produced? This would allow manufacturers to produce uniform sharp edges as opposed to the uneven (though extremely sharp) edges that are produced by simply shattering a piece of obsidian.

You won't (probably can't) get a sharp edge as a product of melting.
Surface tension of any liquid will pull the shape into an energy-saving curve (e.g. soap bubbles being spherical) and you'll always (?) get a rounded edge if melting is involved.

Originally Posted by Dywyddyr

You won't (probably can't) get a sharp edge as a product of melting.
Surface tension of any liquid will pull the shape into an energy-saving curve (e.g. soap bubbles being spherical) and you'll always (?) get a rounded edge if melting is involved.

Now, I was always taughted that glass is an amorphous solid; that is, a very highly viscous liquid, which becomes less viscous as temperature increases, but it cannot be melted.

Incorrect taughts? jocular

Originally Posted by jocular

Now, I was always taughted that glass is an amorphous solid; that is, a very highly viscous liquid, which becomes less viscous as temperature increases, but it cannot be melted.
Incorrect taughts? jocular

I dunno, what word would you use for something sufficiently "liquid" that it can be poured?


"Melted" conveys the gist, surely?

Thanks for the response! I have another question! Could a high powered laser potentially blast the glass rather than melt it to produce a sufficiently sharp edge? I'm not sure if a high powered laser can be as thin a molecule but could a molecular thin edge be produced by blasting with the 'edge' of a thicker laser and moving it (either the glass or the laser) by minuscule degrees (microns or nanometers)?

Originally Posted by ericroe51

Thanks for the response! I have another question! Could a high powered laser potentially blast the glass rather than melt it to produce a sufficiently sharp edge? I'm not sure if a high powered laser can be as thin a molecule but could a molecular thin edge be produced by blasting with the 'edge' of a thicker laser and moving it (either the glass or the laser) by minuscule degrees (microns or nanometers)?

A laser is just light. How can it "blast" anything? What do you mean by "blast" in this context?

Well I've read about using high powered lasers to cut glass for industrial purposes:DPSS Lasers Overcome Glass Process Challenges (Photonics Spectra | Sep 2012 | Features)
That's what I imagine as 'blasting'. Do these lasers rely solely on heat to cut through glass? Anyway could this type of high powered laser, for example USP, be used to shape a fine edge onto a piece of glass like obsidian?

Originally Posted by ericroe51

Well I've read about using high powered lasers to cut glass for industrial purposes:DPSS Lasers Overcome Glass Process Challenges (Photonics Spectra | Sep 2012 | Features)
That's what I imagine as 'blasting'. Do these lasers rely solely on heat to cut through glass? Anyway could this type of high powered laser, for example USP, be used to shape a fine edge onto a piece of glass like obsidian?

From what I read in the article, the laser either removes material by evaporation or heats it, which is then followed by rapid cooling to make it shatter along a predetermined line. You can read for yourself what accuracy of machining can be achieved. I'm not sure how fine the sharp edge of a blade has to be, to be honest.

Ok, I'll do that, thanks! I'm thinking of the sharp edge of a razor for shaving so the finer the better. Obsidian is already used to make scalpels because the natural edge is so fine it leaves fewer scars; that's what piqued my curiosity.

If you've ever broken glass by dropping a drinking glass like a klutz like I have you realize that the shivers of glass can be horrifically sharp. I am always amazed at how sharp broken glass can be, and how easily it can cut you. Broken glass shards are pretty imprecise though, but depending on what application you have in mind, don't be afraid to throw some glass around... with the proper safety measures in place of course.

Hi Sakko, really I'm wondering whether a razor blade made of obsidian could be produced in a factory. So it needs be very precise as well as sharp; otherwise it would be dangerous as well as ineffective as a razor.

There is a process called laser ablation that might be suitable for removing very small amounts of material from the surface of a glass edge to sharpen it. I use a conventional laser cutter and though it will etch glass, it won't go anywhere near doing what you are talking about. I use it for cutting plastic and it removes that by vaporizing it. Focus is critical to the process. The slightest bit out of focus and it doesn't work properly.

Originally Posted by Warron

There is a process called laser ablation that might be suitable for removing very small amounts of material from the surface of a glass edge to sharpen it. I use a conventional laser cutter and though it will etch glass, it won't go anywhere near doing what you are talking about. I use it for cutting plastic and it removes that by vaporizing it. Focus is critical to the process. The slightest bit out of focus and it doesn't work properly.

Thanks for the info Warren! I'll look into ablation, hopefully it can be used to produce a fine edge!