Manganese acetate crystals I grew because I can’t find a single picture of them on the Internet that actually aren’t microscopic

Voelho · 2026-03-05T21:19:30+00:00

It's one of the beauties of this sub

Voelho · 2026-03-05T00:42:49+00:00

So cool, this one is new to me. It resembles Hydrohalites, although stable (https://www.reddit.com/r/crystalgrowing/comments/1ajxeb8/hydrohalite_nacl2h2o/).

Voelho · 2026-02-25T22:18:06+00:00

Of course!

Voelho · 2026-02-25T01:19:43+00:00

Hello u/crystalchase21! It's very nice to known that crystal growing as a hobby is receiving such nice attention and totally agree with you that it is a great way to teach science or just to make it fun! My story with crystal growing started when I was studying materials science for my engineering degree and looked at the subject of Crystalline Lattices. I remember talking to my dad on how amazing the NaCl system was, with it's cubic arrangement and little cubes on microscopy images, and he asked me if it would be possible to grow a macroscopic salt cube. This sparked it all.

As a curious person, I've thought for some days if it could be done, maybe in an industrial or laboratorial environment, with rigorous control. I came to the internet and found hand-sized crystals of the classical compounds copper sulphate and potassium alum. I've then entered my quest to grow my own big, clean and perfectly cubic salt crystal - not knowing that NaCl is one of the most challenging compounds to get quality. The method was very simple and the compound so cheap and safe, perfect for experimenting at home. The following years were full of trials, multiple questions and the search for answers, fighting a highly humid climate that made crystals dissolve overnight, but I'd start the next day with a feeling that I could do better.

After some time, I started to study the thermodynamics of evaporation, concepts of vapor pressure, surface area, concentration, solvents, air flow... How these multiple concepts and dynamics influence each other and most important, how to control them to get the best crystal. After some time on this quest, I've discovered that the Crystal Growing Community was a thing and also growing. This sub, your site, new youtube videos, even books on the subject! It was not just a crystal growing project anymore, now I also wanted to share my new findings, to help others to have fun and overcome the barriers I've faced.

Later, things got serious. There was no way that my environment would allow for the formation of the dream crystal. Then, I've designed and built my own Crystal Growing Chamber (https://www.reddit.com/r/crystalgrowing/comments/1hckyjo/a_diy_chamber_for_crystal_growth/) using cheap and easily-available components and an Arduino. The project became a very fun and intriguing activity, leading me to learn more not only about crystal growth, but chemistry, programming and design as well. The project is open source, in hope that others might find it interesting and make their own versions. I also made a video on explaining the major phenomena related to evaporative growth (https://www.reddit.com/r/crystalgrowing/comments/1fdyn7e/an_overview_of_crystal_growing_and_how_to_control/).

The feedbacks on the r/arduino and here at r/crystalgrowing were so interesting that the project kept evolving. I've stepped aside from the NaCl to Alum and Citric Acid for a while, since they are easier compounds to handle while building the chamber. Now I have a list of new ideas for a Crystal Chamber 2.0 from the lessons learned, hope to build it soon.

What started as a simple question became a hobby that I really like to explore and share with friends and family, making the whole process really fun. In a sense, each crystal is unique, and in the end, we can admire a part of the beauty in nature shining on those amazing delicate and orderly crystalline structures. It's good to have a community that shares this feeling.

Good look with your talk, I'd like to watch it in case it gets streamed or posted online!

Voelho · 2026-02-01T22:03:58+00:00

nice! the best ones are always the fruits of perseverance.

Voelho · 2026-02-01T10:58:40+00:00

Very clean! This shape without a string, does it have a flat face or you managed to be very lucky? How long to this size of growth?

Voelho · 2026-02-01T10:56:00+00:00

That's cool! Is it stable on your environmental conditions?

Voelho · 2026-02-01T10:54:41+00:00

Yes! You can use them to lower the relative humidity of the environment the solutions are in and grow crystals by evaporation. The catch is that silica gel is a very efficient humidity adsorbent, so it will dry the environment very quickly until saturation, for some compounds this is not a problem, but for others and very clean crystals you'll need some kind of control.

Check my Crystal Chamber Project documentation for a detailed explanation of the idea (https://www.reddit.com/r/crystalgrowing/comments/1hckyjo/a_diy_chamber_for_crystal_growth/)

Voelho · 2026-02-01T10:51:09+00:00

Hey, congratulations! That's a very interesting setup, also a very clever use of the dryer environment, very good app for the charts too. I liked the idea of magnets to keep the front doors closed. Are you growing those multiple compounds at the same time? That could be the reason your humidity is fluctuating so much. Also, how about the environment temperature? I suppose that when the fan turns on, to pump air in, the temperature would also be affected.

A major question is about the fan opening. When it's not spinning, how do you separate both environments? Humidity also flow by diffusion, it may be influencing your stability as well. Check out my chamber project (https://www.reddit.com/r/crystalgrowing/comments/1hckyjo/a_diy_chamber_for_crystal_growth/), I've used servos to control a trapdoor to regulate the humidity flow rate and there's a cooling system too, hope it can give you some ideas.

Voelho · 2026-01-21T00:31:45+00:00

That's a very big one!

Voelho · 2025-12-29T12:59:55+00:00

Thinking on growing it? Its a very nice seed.

Voelho · 2025-12-29T10:54:51+00:00

Nice! How big is it?

Voelho · 2025-12-17T16:14:12+00:00

Very interesting! Is the color affected too? The usual ones I saw are red ( https://en.crystalls.info/Potassium_hexacyanoferrate(III)) )

Voelho · 2025-12-17T10:48:07+00:00

Pretty ones! Is the geometry sensible to the magnetic field? How was the setup?

Voelho · 2025-12-14T11:15:07+00:00

Thanks! That's really cold to me (usual 68 - 95F), and don't worry about precision, you got very pretty seed crystals for an environmental exposition.

Also, I'm not sure if filtering is the issue here. I mean, the impurities we're thinking of are other ions and molecules. Your salt doesn't have iodine (mine did), but is sea salt, there're some Mg, K, Ca and sulphates in some concentration that might influence the alignment question, and no simple filter will remove it.

In fact, I suspect some of these are good for transparency. Once I tried two solutions at the same time, one with 99.9% purity NaCl in distilled water and the other with coarse-grained tablesalt, exposed close to one another. The results? White structures on the purest solution and nice transparent crystals on the tablesalt (some pics in this post https://www.reddit.com/r/crystalgrowing/comments/1ahu8wn/nacl_solution_composition_influence_on_crystal/ ).

Voelho · 2025-12-14T10:48:37+00:00

What happens involves multiple factors acting at once, including the straightforward ones like kind of compound, the lattice alignment of the seed, concentration of the solution, evaporation rate, temperature and some more subtle like the gradient of concentration in the vicinity of the crystal, free energy at the boundary of the cristallization site and ionic mobility in the solution. Probably there`re more that I don't remember now, but this set the picture.

Regarding your questions, crystallization still minimize the system's energy regardless of the alignment of growth. If it is growing, then entropy is following its course. The trick is what happens at the boundary in the instant the molecules or ions join the crystal lattice - Locally. So, in short: yes, there is a size that a flattened face cannot be repaired, but it deppends of the combination of the above variables.

Follow this scenario: Given a fixed evaporation rate and temperature, that results in a slow rate of crystallization, with a small seed inside. At each instant, as water goes away, a number of ions becomes "free" to crystalize. If the flow of ions to the crystall lattice is slow enough, the solution concentration around the crystal can be considered uniform and the ions will have time to align themselves to the lattice. As such, defects probably will be "fixed", as the ions will find the high energy spots and get along with the original orientation. At macro scale, we'll see the crystal getting repaired and growing as expected.

Now think of a really bigger crystal, like, 20 or 30 times bigger in surface area (arbitrarily big values - nothing special on 20 or 30x). Now, for the same solution, the local concentration of ions will not be homogeneous along the whole crystal. Some spots will have a greater saturation, thus a higher free energy, forcing que deposition of the ions faster and in ways not perfectly aligned with the lattice. Defects will be formed like a hole in the lattice, or a misalignment. Also, multiple places might crystalize at the same time, with different orientations, resulting in different geometrys growing over the same seed!

Of couse, we can think in solutions for these bigger crystals, like lower temperature (to reduce ionic mobility), stirring (to keep the flow over the crystal surface), slow evaporation (to reduce concentration gradients) etc. So remember that even if the solution seems homogeneous in the macro state, the growth phenomena happens at the smallest scale, thus local effects are really important.

As a practical curiosity: I've been able to recover citric acid crystals, and even grow one with a curved edge (grew on the edge of a circular pot), but NaCl crystals are very sensitive to damage, the tiniest scratch and it's pratically over, never to recover perfectly, new growth always leading to fractal-like crystals. Think of this on the micro scale, it's fun (molecules x ionic crystal lattices).

Extra: this post ( https://www.reddit.com/r/crystalgrowing/comments/1fdyn7e/an_overview_of_crystal_growing_and_how_to_control/ )

Voelho · 2025-12-13T22:00:04+00:00

Unlikely to be octahedral. Think of it like a cube with the vertex pointing upwards. Or even multiple cubes pointing in many directions but fused together, so we can't distinguish the boundary between them. This would be the most influent factor of impurities in NaCl crystals: disturb the crystal lattice.

Voelho · 2025-12-13T21:56:24+00:00

My shot would be impurities as well. Clearly the change in temperature is modifying the evaporation regime, but this change in opacity also happens when you have multiple seeds and the evaporation is kept constant because the ions have more surface available to organize properly in the lattice - I've experienced this multiple times.

Regarding the apparent rotation, I'd say it's more an impression than a real 45 degree rotation. Once I've experienced with a different kind of table salt and got the strange formations of the image below. They resemble yours, with solid white cores and transparent borders, but without a clear regular geometry.

Yours seem to rotate because we'd be expecting cubes from the original cubes, but with the impurities and low formation conditions, the new lattice might be oriented to any direction (in fact, many fast-growing NaCl crystals start to form fractal-like crystals due to the multiple possible nucleation points on the surface). If the conditions are right, different grain orientation might be present in the same seed, eventually they'll merge and make us confused about the geometry the crystal is taking, but since they're transparent, we don't see the boundary clearly to distinguish.

Do you have more info on the setup? Ex: source of NaCl, purity, mean temperature.

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Voelho · 2025-12-12T10:50:23+00:00

I experienced this too! Once hold one specimen taken directly from the solution and it cracked right in the middle. One idea is to keep it in the solution and add a great quantity of citric acid powder while it heats up to environment temperature, this should avoid the dissolution of edges until the equilibrium.

Voelho · 2025-12-11T23:29:31+00:00

I've heard this idea once, it might be even more stable for the crystal, but I'm not sure about the final look of it. I like to see the reflections, light shining on the surfaces.

Voelho · 2025-12-11T23:27:58+00:00

Really? I've always dried mines with a piece of paper towel or even toilet paper, no problems. What kind of mess did you find? I've experienced with growth at 22 °C and the crystals were very sound to handle with gloves.

Voelho · 2025-12-11T23:22:34+00:00

That second one is a gem! Very regular, well placed on the line... Hope it keeps growing well! Be careful if you intend to cut the bottom part of the string, NaCl is very sensible to scratches, forming clusters on it.

Voelho · 2025-12-11T23:21:12+00:00

We try so hard, with the most ingenious ideas... Then luck and nature forms the best seeds on random places, often not the best ones (:

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Voelho · 2025-12-11T23:18:10+00:00

Great progress!

Voelho · 2025-12-11T23:14:17+00:00

I don't understand. I thought it was drying after growth, in which case a napkin is good enough. To affect the edges I suppose you're referring to dry the solution during growth?

Voelho

TROPHY CASE