v0.34 Talk:Obsidian

Its very likely that the wood is used for both the handle and the blade, with the obsidian flaked in long pieces and set in the wooden blade. A weapon like this was used by the aztecs. – unsigned comment by Dianetics

It has been known for years that rock swords are intended to be these; in Dwarf Fortress, though, it just treats the item as a sword made entirely of Obsidian because items cannot be made of multiple materials. Also, please sign your comments. --Quietust 12:40, 15 April 2012 (UTC)

There is a bug currently with obsidian swords here. I verifed that this bug still exists in 0.34.11 by adding IS_METAL to obsidian to permit the creation of obsidian swords in the arena. I also verified that adding glass-like SHEAR values to obsidian permits swords to cut up creatures rather than clubbing them.

I found a research thesis online in which the material properties of obsidian were tested. Note the biaxial strength (in this case, tensile stress in both directions) of 35 ± 6.7 MPa for black obsidian. This would be equivalent to [TENSILE_FRACTURE:35000]. More importantly, setting the shear values would permit effective weapon usage, i.e:

[SHEAR_YIELD:35000] [SHEAR_FRACTURE:35000] [SHEAR_STRAIN_AT_YIELD:114] shear modulus 30.7 GPa

For comparison, green glass is currently this in DF: [SHEAR_YIELD:33000] [SHEAR_FRACTURE:33000] [SHEAR_STRAIN_AT_YIELD:113]

--UristDaVinci 05:28, 30 June 2012 (UTC)

Surviving casting

I've never seen anything survive casting in obsidian. Has anyone seen this happen before? It appears to have migrated from v0.31, so it's possible that it's outdated. I might as well remove that sentence if nobody has seen it happen in v0.34. --Lethosor (talk) 02:32, 2 March 2013 (UTC)

A surprising amount of stuff can indeed survive casting. I dumped a wide variety of clutter into an obsidian casting chamber, added water, then poured magma over the top. All the constructed furniture remained visible on top of the obsidian (including wooden cages and a leather bag), but the loose items were hidden. Excavating the obsidian revealed a wide mix of loose items that survived, including leather, fat globs, logs, piles of thread, barrels of alcohol, clothes, finished goods, and copper equipment. It appears that the majority of items survived the experience (and I didn't notice anything that suffered wear).

After the first run, I sealed the chamber back up and dumped in a splash of magma first, followed immediately by water. This time there were significant losses, and much of the fragile stuff that remained showed heavy wear from fire/magma. Some built and unbuilt non-mamga-safe metal cages survived, as did an animal corpse that was in one of the built wooden cages (the wooden cage itself was destroyed). Some built and unbuilt non-magma-safe stone furniture also survived. At the leading edge of the obsidian flow I uncovered some clothing and logs that apparently survived the casting process, though somewhat worse for wear (and some apparently still smoldering!). A few other flammable items survived being lit on fire and doused with water (without actually being cast in obsidian), though with heavy wear.

Based on these results, it appears that magma/fire interaction is responsible for the majority of items destroyed, not the obsidian casting itself. It's probably possible to use the DFHack "liquids" command to verify these results and perform more controlled experiments without creating complex casting chambers. --Loci 21:34, 3 March 2013 (UTC)

I suppose my question should have been "has anyone seen clothing survive obsidian casting?", since this is what is unverified in the article. Most items I'd tested weren't exactly "strong", but it makes sense that stronger items would survive (although how they could be mined out safely is interesting). It looks like the "unverified" part was indeed incorrect, if some clothing can survive.--Lethosor (talk) 02:45, 5 March 2013 (UTC)

I just had some dragon tallow survive the magma and obsidian casing (I dumped a lot of unecessary tallow). After this i'd bet that even their meat is magma-proof 177.133.48.34 07:25, 1 June 2013 (UTC)