Saw a video of a person pulled a shard of metal out of a liquid, looked really cool and wanted to know how they form?
In: 24
I’ve made what is quite possibly over a thousand Bismuth crystals myself, so let me state a little bit on the how and why (as it got a bit too long for reddit, I had to split it into two parts: How and Why:
**The bismuth:**
What you want to do is find a suitable container and melt some pure(!) bismuth in it. For beginners, a kilogram is enough; the stuff is quite dense, though, almost exactly 10g/cm³, so that kilogram is 1/10-th of a liter. It needs to be quite pure, ideally 99.999% or more (99.99% usually is fine), for the beautiful not-actually-a-rainbow colors to form. For just the shape, somewhat less purity should still work. If you want silver crystals you can actively add 0.1% to 1% of tin to it (be aware that you will never be able to get it removed again!), or remove the colored oxide layer with a few percent hydrochloric acid.
**The equipment:**
The container should not be more than half full for safety; less is usually fine, the molten soup should however be at least 2 cm deep for basic crystals. Stainless steel pots, cast iron cookware or uncoated frying pans are okay. Do not use them to prepare food ever again. Bismuth, while quite non-toxic for its kind, is still a heavy metal, and other impurities add to it.
You also want a few things to poke at it, clean the surface, and most importantly, pull out crystals. Even simple cutlery, forks in particular, work reasonable well. At least one suitably sized tong and a metal hammer are recommended.
The hammer is to help remove bismuth that hardened on your utensils. You will have to wait until it cools, the still-hot bismuth is too ductile to be hammered off. It is however quite brittle when cold.
I strongly recommend against copper, galvanized steel or weird materials you don’t know, because the bismuth can and will dissolve their surface. This not only may destroy them, it definitely will make your bismuth less pure and you almost certainly do not want that!
Next I strongly recommend some safety goggles (almost any material will do) to protect your eyes in case of a stray splatter of molten metal. Or whatever other mishap that could happen. Better be safe than sorry, they cost as little as 3 bucks and that’s definitely cheaper than an eye.
In addition, heat resistant rubber gloves (those for 350 °C and more) work quite well to protect your hands and to touch hot things. I’ve even quickly(!!!) grab into the molten metal a few times with them, but you need to be _very_ sure that there are no holes for obvious reasons. Do never use ones made from cloth-like substances, in particular if they are not water-tight, as the molten metal will seep through them to your flesh; even worse, now you have metal-soaked stuff directly on your skin.
Lastly, you want a surface where you can put your freshly minted crystals to cool down. Silicon mats, for example. Or an old plate. Anything that resists 300 °C goes.
**The melting:**
You need to heat the entire amount to at least 271 °C, so you want a method to heat the container that can provide at least 300 °C. Many simple cooking plates can (barely) do. It is faster if you use gas or induction, but you should be careful to not heat it way too high as this will cause harmful metal vapours. If you have a fitting one, a lid can help to speed it up quite a bit.
After all the stuff is molten, you stop heating and let it cool; the fun part begins!
**(Optional: Clean the surface)**
You can now try to remove the slag from the surface. It’s a mixture of impurities, dirt,bismuth oxide, and some molten bismuth. I recommend a fork.
**Method 1: Fishing!**
This is the method I would recommend for most people, it is safer, easier, and gives you exactly what you probably had in mind to begin with.
Bismuth is one of the few elements that, like water, is less dense in solid than in liquid form. In other words, the non-molten stuff swims on the surface. This is not only neat, but also quite useful:
While slowly cooling down, you will notice triangular and rectangular patterns on the surface. These are your first simple crystals. Don’t get over-exited yet, they are initially quite flat and need a bit more time to grow. Give them some time, but not so much that they connect to the container’s edge or bottom. The perfect waiting time depends a lot on your setup and is the tricky part, it simply needs experience.
If you think you might have something in there, you can poke it slightly to get a feel for its size. Do not do that too often, it disturbs the growth. If you feel confident about its state, grab it with your tools and pull it out. You don’t need to be extremely quick, you can take a few seconds. Don’t take literally forever, though, it will lead to ugly crystals. Do avoid to put any part that has already left it back into the molten metal, it will simply form an ugly layer (sometimes it can be stripped off when cooled down later).
Lay it down onto some suitable surface and let it cool. Depending on size, your first crystals will most likely turn into a still quite beautiful orange-golden-purple color scheme. Later ones can get all the colors, especially if they cool down slower by various means.
Congrats, you got your first crystal(s)!
As a variation you can put a small object inside that acts as a “seed” for bismuth to grow on. This may be anything from a little piece of bismuth, a steel ball to a wire poking into it. It should satisfy the same constraints as the container regarding materials. It needs to sit still, so holding the wire yourself is not an option, it needs to be affixed somewhere.
Despite being called a seed, it however only acts as a starting and slight cooling point. A proper seed for crystal-growing means that it is a small crystal that then simply grows larger; this is how many crystals are grown. This is not what happens here! Even if you use a bismuth crystal, it will already have a protective oxide layer that prevents this from happening. It simply won’t work out this way.
**Method 2: Pouring!**
This one is used to make so-called “geodes” and also basic crystals that look slightly different. It needs more equipment and is more dangerous as you will pour 300 °C hot molten and quite dense metal around!
You will need a second container, maybe even a third. It should be one that only gets wider to the top for reasons you will soon realize.
Put on some protective gear, i.e. gloves, and pour molten metal into the second container. Make sure that it is standing very sturdy and safely on a flat surface for it not to topple in any way! This happens much easier than with water due to the high density of bismuth!
Now like in the first method you wait some time until some of the bismuth has hardened. At the right time, you pour the still-molten metal away, usually back into the first container; or into a third to repeat this step there immediately. Depending on what you want, and mostly experience, you either just pour when the surface begins to harden in the middle, or shortly before the last molten hole on the top closes up.
Let it thoroughly cool. This takes a long time, possibly even hours. Then get whatever you made out of the container. This is where you are screwed if your container does not widen to the top. Even perfectly vertical containers will usually get it stuck. If you did the first option (pour while most surface is still liquid), you can alternatively break interesting crystals off and then re-melt inside the new container.
**DANGERS!**
It should be obvious and common sense that molten metal at ~300 °C is not exactly safe unless handled carefully:
– Do not have children and pets around; they can and _will_ cause issues.
– Avoid every getting in contact with the molten metal. It will hurt. Severe burns are quite possible.
– Also don’t touch still-hot bismuth or the hot parts of your equipment. It will give you typical burns.
– Do not inhale the vapours. Do it outside or in a well ventilated area. Do not heat the metal hotter than necessary.
– Wear protective gear (gloves, goggles) whenever appropriate. For goggles this means: **always**.
– Be especially careful if handling or moving larger amounts, like with the pouring method.
– Absolutely(!) never(!) feel tempted to cool molten bismuth with water. It will effectively explode and shoot hot water, steam and metal everywhere (maybe surprisingly, the hot water is more dangerous than the metal). Do not even attempt to cool solid bismuth this way until you are sure there is definitely no molten metal left anywhere.
However, some things apply that make it typically less dangerous than what many fear, as long as the above things are taken into consideration:
Bismuth is one of the least toxic heavy metals. [It is even part of OTC stuff](https://cloudinary.images-iherb.com/image/upload/f_auto,q_auto:eco/images/peb/peb03991/l/23.jpg). Eating it is obviously silly, but accidentally ingesting small amounts, e.g. as dust, should be harmless (not a medical doctor here!).
Small splatters that hit normal skin only prick a bit and rarely leave any marks, especially not permanently. This is because bismuth has a relatively low thermal conductivity and capacity for its kind. Hot water is actually way worse. I’ve got a few smaller but permanent brandings in my forearm from working with bismuth, and all of them are from accidentally touching hot equipment, hot water, or still-hot crystals, and are all due to stupidity. None came from molten bismuth. Take this as you wish, but be still careful!
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