#video on #casting bronze with sand cores made from sand and 5 wt% #waterglass #materials rather than, as in his previous video, molasses and flour. He got his waterglass from a pottery supply store and gas-cured it in a ziploc. He’s using hose clamps on a split pipe for his mold for the core. With 5% he can still break it by hand after curing.
on 02025-11-14#PDF of Sagnak’s #dissertation #paper on geotechnical soil stabilization for civil engineering using recycled gypsum and sodium silicate (#waterglass). It mentions that bacterial soil stabilization (using carbonates) has been widely used since at least 01999, long predating the tafoni project and Biobricks.
on 02025-04-12a kilogram of sodium metasilicate #waterglass costs 140 rubles. #materials #pricing
on 02023-03-10this explains the whole #waterglass insolubilization thing.
on 02015-08-30Common rust is iron(III) oxide (ferric oxide), so it won’t work to cross-link #waterglass, but magnetite has some iron(II) (ferrous) in it, and wüstite (FeO) is pure iron(II) oxide (ferrous oxide).
on 02015-08-30apparently you can dissolve #potassium-silicate in water more easily than sodium-silicate #waterglass, which usually requires pressure cookers to dissolve it. Also apparently potassium-silicate binders make mortar #thixotropic!
on 02015-08-30Goodness, this "potassium silicate" sounds a great deal easier to produce than #waterglass; potash plus silica at 90°C! And it should still work as a silicate donor for insoluble silicates like calcium or magnesium silicate.
on 02015-08-30how to use #waterglass as a binder or coating.
on 02015-08-30Oh wow, one of the hazards of #waterglass is that it “can etch glass if not promptly removed”. Also helpful: “Do not store in aluminum, fiberglass, copper, brass, zinc, or galvanized containers.” Well, I guess that leaves steel, iron, and polypropylene, huh? pH of 11.3 with a 37.5%-by-weight solution of sodium silicate.
on 02015-08-30YES, apparently you CAN precipitate #waterglass with magnesium salts. But you get AMORPHOUS magnesium silicate, as a fine powder. #materials
on 02015-08-30Oh my. You can fire #talc to turn it into #enstatite and cristobalite at 1000° to 1200°. Be still, my beating heart! So you could maybe precipitate #waterglass with magnesium to form talc, machine the talc to precise dimensions, and then fire it to dehydrate it and precipitation-harden it into enstatite and silica? And then it’s refractory enough to cast silver in? That’s AMAZING. Can you also reinforce it with some kind of refractory fiber, like basalt fiber (declassified 1995!), as you precipitate it, so that it will have reasonable tensile strength? #minerals
on 02015-08-30No, wait, "forsterite" (an #olivine; Mohs hardness 7! Gemstone peridot!) is magnesium silicate, Mg₂SiO₄. I thought that was talc? Apparently talc is hydrated, so I’m guessing that precipitating #waterglass with magnesium is going to give you something more like talc than like forsterite, which also has a 2:1 Mg:Si ratio, compared to talc’s 3:4 Mg:Si ratio; so baking out the water probably wouldn’t be enough. #Refractory #materials: doesn’t melt until 1900°! (And iron ions, but only iron(II) ions, can replace the magnesium in any concentration.) But wait! There’s #enstatite! #materials #minerals
on 02015-08-30"Olivine" is magnesium iron silicate, which is I guess what you get if you precipitate #waterglass with magnesium and iron salts? Or will the hydration interfere with that and give you a softer and weaker material, like talc? #minerals
on 02015-08-30"Larnite" is calcium silicate, so I guess that’s what you get if you precipitate #waterglass with calcium salts. It’s Mohs hardness 6, a lot harder than talc. Occurring as a phase in concrete, it’s called “belite”. “readily prepared from reactive CaO and SiO₂ at 300 °C.” #minerals
on 02015-08-30Talc is hydrated magnesium silicate, H₂Mg₃(SiO₃)₄, so I guess that’s what you get if you precipitate #waterglass with magnesium salts. (Or not; see below.) #minerals
on 02015-08-30#waterglass nonahydrate is “efflorescent sticky crystals”, while amorphous and pentahydrate are pellets. “Sodium metasilicate, International Programme on Chemical Safety, Poisons Information Monograph 500” #toxicology
on 02015-08-30is an MSDS for #waterglass giving its pH as 12.4 in a 1% aqueous solution in the nonahydrate form.
on 02015-08-30Sodium Metasilicate, Anhydrous [6834-92-0], Sodium Metasilicate Pentahydrate [10213-79-3], and Sodium Metasilicate Nonahydrate [13517-24-3] Review of Toxicological Literature, January 2002 (sodium metasilicate is sodium silicate, aka #toxicology #waterglass.) Notes that you can recover the metasilicate from ordinary silica gel by adding an alkali, such as sodium hydroxide, which sounds a lot easier than the silica-sodium-carbonate reaction at 1400°. Also notes that it’s sufficiently alkaline to be corrosive to many metals.
on 02015-08-30