Sciencemadness Discussion Board

Melting Obsidian?

elementcollector1 - 14-4-2018 at 20:18

I was wondering if it'd be possible to melt a larger quantity of obsidian into a solid block, in the hopes of carving something out of it. Unfortunately, the pieces I have are just a touch too small for the object I want to make, so I'm going to have to get creative if I want to succeed.

From here, I've got two options:

1) Obisidian powder + binder. While I certainly have the tools to make this possible, I'm unsure if it would look good or pass for a chunk of the natural thing. I'm aware that a good deal of mineral specimens sold in online shops are actually 'reconstituted' - powdered and mixed with a clear resin binder, followed by rigorous polishing to once again resemble a stone - but I'm not sure I can copy their process well enough to warrant wasting my stock on this.

2) Melting obsidian pieces/powder together. I don't have the tech for this right now, but I'm thinking one of those DIY arc furnaces from microwave transformers (which I do have the materials for) might suffice, if I can melt a sufficient quantity at a time. I'm also worried that the obsidian might turn white upon melting, or lose its vitreous texture, or some other thing that would completely ruin the whole attempt.

Thoughts? I know this is a pretty unusual question, but I'm hoping to create something pretty unusual, so I felt it appropriate to ask for help before jumping in.

JJay - 14-4-2018 at 20:38

You could probably melt it with a Fresnel lens.

mayko - 14-4-2018 at 21:00

Once hot, glass is electrically conductive and can absorb microwaves, which in turn heats the glass. This can melt holes in bottles and such. I wonder what obsidian would do if you gave a spot of it a blast from a MAPP torch and microwaved it?
http://amasci.com/weird/microwave/voltage2.html

barbs09 - 14-4-2018 at 22:14

Technically you don't need to melt obsidian to make obsidian as by definition obsidian is simply the rapid cooling (quenching) of a felsic melt. Felsic being of a broadly granitic composition.

So you could melt granite rather than trying to source obsidian. Arc furnace??

unionised - 15-4-2018 at 00:46

I think the biggest problem you will face is making sure that a big block of glass cools evenly enough not to shatter.

Bert - 15-4-2018 at 01:46

How in are you going to CARVE obsidian? Primitive shaping was by striking off "cores" from a natural block, then pressure flaking those cores to desired profile as was also done for flint, chert & etc.

As noted by unionised, you probably need an annealing oven to produce stress relieved blanks for carving large objects.

unionised - 15-4-2018 at 01:58

This is not a practical solution; but it's cool.
https://www.youtube.com/watch?v=hv3jeGUv9fY

Morgan - 15-4-2018 at 06:26

Something about bubbles, maybe another thing to contend with ... ...
https://chemistry.stackexchange.com/questions/74534/melting-...

elementcollector1 - 15-4-2018 at 11:38

Sounds like resin and powdered obsidian would be the way to go, then. Hopefully I can powder it fine enough and mix it thick enough that it resembles the real thing again by the end.

OldNubbins - 15-4-2018 at 20:48

I have melted obsidian and it essentially foams up due to trapped gasses and water. It resembles perlite - which it probably is since it is formed from hydrated obsidian. Our property is near an old volcano and have obsidian all over with boulders up to the size of a small car. So if you are near California, I could hook you up.

elementcollector1 - 15-4-2018 at 20:56

I'm... somewhat close to California, up in Washington. Obsidian's rather heavy to ship, though, especially in these quantities...

VSEPR_VOID - 15-4-2018 at 21:17

If you do so happen to make molten obsidian make sure to add it to the List of Chemicals and Materials Made by Sciencemadness.org Users

https://docs.google.com/document/d/1AoI2VA5L4bmFw2HwXS2OVYTV...

Bert - 15-4-2018 at 21:22

How much obsidian do you NEED?! The batterang doesn't require all that much... If resin bonded obsidian fills the bill, why even bother to use it to fill the resin? Black resin castings are dead easy.

Old nubbins, I am intrigued. Fascinated by obsidian since the first time I ran across "apache tears" at the rock shop in Madison WI, back in the 1960s. I wouldn't mind a nice nugget, head sized or so? Would gladly pay postage to 55063. U2U if you want to hook me up-

[Edited on 4-16-2018 by Bert]

elementcollector1 - 15-4-2018 at 21:26

Quote: Originally posted by Bert  
How much obsidian do you NEED?! The batterang doesn't require all that much... If resin bonded obsidian fills the bill, why even bother to use it to fill the resin? Black resin castings are dead easy.

[Edited on 4-16-2018 by Bert]


Not making the batarang, but rather a few larger pieces. Besides, why would you want a black resin casting when you could say you have a giant thing made of real obsidian? It's novelty more than practicality.

OldNubbins - 15-4-2018 at 22:29

Quote: Originally posted by unionised  
I think the biggest problem you will face is making sure that a big block of glass cools evenly enough not to shatter.


You probably won't have to worry about that. It cools fast but under intense pressure - which is why it foams when heated due to trapped water and gas. It fractures readily but doesn't have any localized stresses to speak of - any obsidian you find has already fractured off it's original 'monolith' and has been geologically abused for some time. I have carved and knapped quite a bit of this stuff and a wet tile saw and a dremel work great for shaping. The worst that has happened is hitting an inclusion or internal fracture, an unexpected chunk separates from the main body, and you are forced to reconsider the design...

Morgan - 16-4-2018 at 06:17

I wonder if you'd have to vacuum bake obsidian to get all the bubbles out when melting? There's this eBay listing that came to mind.
"You are buying one bundle of quartz tubing with 20 sticks per bundle.
This is ultra pure with a 40 hour vacuum bake."

[Edited on 16-4-2018 by Morgan]

Bert - 16-4-2018 at 07:28

Quote: Originally posted by elementcollector1  

Not making the batarang, but rather a few larger pieces. Besides, why would you want a black resin casting when you could say you have a giant thing made of real obsidian? It's novelty more than practicality.


Sorry, when it sounded like you were going to glue together a composite, I went into movie prop mode.

It is a fine madness. A shape made from a single piece or a thermally fused mass should be good for some geological ages, barring getting smashed.


[Edited on 4-16-2018 by Bert]

elementcollector1 - 1-5-2018 at 21:37

After some careful consideration (and a few mouthwatering pictures I stumbled across), I've instead decided to make the objects out of blue goldstone.

However, I unfortunately lack a recipe for this - all I know is that it is a glass-based material that, unlike red goldstone (which has macroscopic copper crystals in a clear glass matrix, and involves reducing copper oxide with 'other metal oxides' (Wikipedia) in a silica matrix), substitutes macroscopic cobalt crystals in a deep blue, nearly black cobalt-glass matrix.

I'm aware of how to make cobalt glass in varying shades of blue (it just so happened to be a lab exercise a year ago for one of my college courses), but I'm unsure what one would add to reduce some of it to elemental cobalt in just the right crystal size to produce the 'glittering' effect. Does anyone else know of a source I might find a more detailed recipe of?

Oh, and here's some pictures for you to enjoy:

100_0715.JPG - 66kB

blue-goldstonev2-600x600.jpg - 70kB

blue-goldstone-crystal-egg_1.jpg - 27kB

[Edited on 5/2/2018 by elementcollector1]