Kitchen knife made by cooking sand in a microwave oven

Explanation from the youtube comments:

Once again, here's what's going on for you curious people :

Sand (at least in japan) frequently contain tiny specks of magnetite, which chemically speaking is Iron oxide (Fe3O4). As the name states, it has magnetic properties, so you can separate from sand easily with a magnet.
Sand in general is made of a lot of stuff, part of it is made trough rock erosion, and an other part is shell fragments. most rocky stuff are Silica Oxide + some metallic element, and depending of the temperature and pressure at which they solidified their atomic arrangement can differ.
anyway, the white/clear crystal things are quartz, almost pure SiO2. As you probably know, that's what glass is made of.

after preparing some iron oxide and quartz samples, he uses his whetstone to prepare a very thin Aluminium power, tortures an innocent chick, proves us that his fingers do in fact at least use to belong to a human being, and then mixes the aluminium with the iron oxide.

since his iron oxide is in pretty big specks, what he makes it essentially low grade thermite. for those who don't know, aluminium has a higher affinity for oxygen than Iron, so you can get the oxygen to jump to the aluminium. the difference in oxygen affinity means that there is a difference in potential energy, when the reaction occurs all that energy is released in its "raw form" : heat, and a lot of it. That's why thermite was used during the war to destroy machines you didn't want falling into enemy hands.

The reaction is actually pretty hard to activate, so i'm surprised a microwave can do the trick but why not. the result is a nice clump of raw iron and some aluminium oxide (alumina). the iron is magnetizable so it reacts to a magnet, while the aluminium oxide forms the slag, is it brittle and not magnetizable.

the shiny blue specks you can see at 4:10 are not "gems" that spawned from nowhere, it is sand impurities that came with the magnetite, the heat melted them into glass, and whatever impurities they contained gave them the blue color (it can also be aluminium or iron from the reaction.)

He then calcinates the sea shells : as i explained in a previous video, sea shells are essentially calcium carbonate CaCO3, under extreme heat one CO2 is ejected, leaving CaO, quicklime (the video says calcium carbonate but that is a mistake). just as last time, this molecule hates itself and reacts with water to form Ca2+ 2OH-, so the solution is very basic. this reaction also releases heat.

This time rather than using this stuff for its "basicity", he dries it up to get Calcium dihydroxide powder Ca(OH)2. that's literally the same thing but not in solution.

He chars the flowers out of pure spite. they're probably friends with the chick anyway. that will teach them !
pretty sure the shelf witnessed everything, let's get rid of it too. an added benefit is that you have a bunch of carbon and ash now. the color of what he crushes at 6:23 is odd to me, but i think that's what it is.

wood contains a lot of carbon, sure, but plant cells also contain a bunch of ions, just as any cell does.depending on the kind of wood the ashes will contain different proportions of the same things but you will get mostly lye (NaOH) and potash lye (KOH). There is other stuff too but those are probably the most prominent. Because elements of the first column of the periodic table really just want to get rid of one electron so they can have a nice smooth outer electronic shell, all of that will dissociate into water as Na+, K+ and OH-, the latter being what basicity truly is. actually there should be a fair share of calcium in this mess but whatever, it behaves pretty much the same here.

accordingly, the solution is basic, although 13-14 is pretty damn high for ashes in water if you ask me. he probably had to do a few batches, evaporate some water and pool them back together to get that. after drying the filtered solution, he says that is sodium and potassium carbonate, but i don't see what guarantees that, it could also be lye and potash back again for all i know. Supposing he's right, that means precipitation with carbonate ions occurs faster. chemically speaking CO2 (from the fire) + OH- makes a carbonate group (HCO3-) that will complex with + charged ions and precipitate.

Now he mixes some quartz, some calcium hydroxide and some Na/K whatever this is. long story short, he's making glass. glass is mostly SiO2 just like quartz, but to melt it you need flux, that's what calcium hydroxide and the other stuff are. Flux is used in metallurgy and glass-making to lower the melting point of things. don't ask me how it works, i like to learn weird stuff but there's a limit even to that :-/

okay that worked, now let's break that glass and turn it into glass power so it's easier to re-melt. there's a reason why people made rock tumblers rather that shaking stuff by hand, but i suppose having no girlfriend since the previous episode increased his...ability to do so ;-)

anyway, while he's at it he prepares some powdered copper to add to the glass for an hopefully nice color. he needs it to be oxidized apparently, so in the nuclear-powered microwave it goes. that makes a nice deep blue color, pulverize this blue glass again and wha- what the hell is he doing ? that's not going to react with water. what is this white powder ? having actually seen the video entirely before typing, he is preparing different grades of "sand" that will sediment at different speeds, but that came a bit from nowhere.

at some point this is supposed to become a knife, and incredibly enough he decided to not go with a handmade glass blade (probably impossible to sharpen without breaking), so it's time to forge that iron clump into a blade ! heat, hammer, repeat, quench for hardness.

from that point he is just making the knife, but actually it was really unclear what he was doing because he skimmed over it pretty fast. the elastic thing at 17:30 confused me because i thought it was the result of the UV resin, but it's it not. it's just some stuff he will use as a placeholder for the aquarium part of the blade. he puts it in place and then pour more UV resin on top.

after sharpening he re-applies some UV-resin to fill in the scratches in order to have a nice finish, breaks the handle of a second half-knife and completes the build by putting the different sands inside. he also puts in a tiny bit of hand soap to make the bubbles more stable so that the sands move in a more interesting way.

now he just has to murder the first cucumber-carrying girl he can find !

Don't be put off thinking it's some weird ASMR thing; I am so glad I spent the full 20 minutes watching. It felt a bit like Dr. Stone, taking things like shells and transforming them into basic chemicals, combining building up to get the desired result. The end result was even more interesting than I could have imagined.

This is so cool, but also really weird.

Thanks, it brightened my day!