Crystal Wonder

In a recent pewter casting session, I cast a yoni-lingam (and two Venuses).

It came out pretty well, but what was of special interest was the tiny crystal formations on the yoni-lingam, where the lingam meets the yoni. (No crystals on the Venuses.)

Alex said that the crystals might depend on different rates of cooling of the object in the mould. So maybe that part cooled more slowly and it allowed these little crystals to form. Cool!

Cool enough to inspire a little study of crystals: what they are and how they form. And then -imagine!- how fortuituous that a few weeks later my daughter and I should discover this crystal-making kit on the sidewalk outside a neighbour's house, sitting there for the taking.

So we mixed up a solution on the stove called "Red Ruby Geode" (aluminum potassium sulphate). We poured in the crystals and then stirred to dissolve it in the heated water. Because warm water increases the material's solubility, the solution gets saturated. When the water is cooled down, the "extra" material that the cold water can't contain falls out of the mixture and forms crystals.

Solution and container with a string to aid in the crystal formation.

Okay, but what is a crystal? According to this do-it-yourself-at-home article from Scientific American:

"A crystal is made of molecules of a product that have come together in a specific repeated pattern. When the molecules of the crystal come together, other products that are often considered impurities, or the unwanted products of the chemical reaction, do not fit well into the structure, much like the wrong piece of a puzzle does not fit. If the crystals form slowly enough, the impurities will be rejected because they do not fit correctly, and instead will remain in the water."

Slow-forming crystals are therefore larger and more cube-like, whereas a solution that is cooled too quickly will produce more crystals but they will be smaller and less cube-like (because they contain more impurities).

Photos from my cheap microscope of the Ruby Red crystals we produced.
Hard to tell which ones were slow-forming and which cooled faster, but it was fun to try.

So, if I understood correctly (if!), it seems that that part of the yoni-lingam cooled more slowly, perhaps because it is covered slightly by the umbrella shape of the upside-down yoni. And because it cooled more slowly, large, chunky crystals appeared. Now, crystals formed everywhere else on the object too--because in any case metal itself is a crystal--but they are so small that they aren't really visible as such and just appear (to me) as, well, "metal".

In "Practical Casting" by Tim McCreight, I found a section on "Recrystallization" in the chapter on Sprues:

"As metal cools it falls into an organized pattern in a process called recrystallization. In the same way that an orderly stack of bricks takes up less space than a disorganized pile, the metal contracts, or takes up less space, as it cools. Small colonies or grains of crystals organize themselves independently, creating microscopic voids between them, that will remain in the casting as pits unless they are filled. If molten metal is available, it will be drawn by osmosis into these spaces, filling in the pits.
If a thicker section is adjacent to the cast object, this will cool a split section later than the piece and will provide a supply of molten metal to fill in the voids. When this largest secion is recrystallizing there is no supply of molten metal to fill in the voids, so it will end up with pits. The aim of proper casting is to arrange sprues so that this happens outside the cast object..."

So there you have it. We learned something about crystals, had some fun in the kitchen, and give thanks to our neighbour and to Fortuna herself for leaving "Crystal Wonder" out for us to pick up.