Natron Theory 🪨 Geopolymer🫟 Megalithic Mystery

And here's me running my mouth and doing nothing: I cast this limestone block a year ago, in the summer of '25. As you can see, it's still in one piece, but I wouldn't call it indestructible. This recipe needs refining. The binder was plain potassium hydroxide, which has since partly leached out and partly carbonated. On its own, that didn't give a strong, weatherproof bond. Another mistake: the limestone I used was too fine and too pure, 99% CaCO3 (that's what I could buy), so geopolymerisation couldn't happen at all, for lack of aluminium oxides, i.e. clay. And yet look: right here, where I'm tapping, a much harder stone formed that doesn't crumble. How is that possible? It's the same 99% pure material, and here it set. I know the secret! I started casting the whole thing with potassium hydroxide, which ran out at some point, so I filled the rest with a sodium hydroxide mix. Both crumble, but at the boundary, where the two lyes accidentally mixed, a much harder material formed! The explanation? In the mixing zone, after carbonation, DOUBLE SALTS formed (KNaCO3), which give a far more stable bond than pure K2CO3 or Na2CO3 alone. Ta-dah! We learned something again! Another stone recipe from the "who would have thought" category! Is this fake limestone salty there? Salty. But who's going to lick it! (By the way, I wouldn't start from 99% pure limestone again: it lacks the material needed for geopolymerisation.)

Ancient stone DIY kit! Try it out!