How I Made an Iron Sulfate Crystal Ring in Just 3 Days

I discovered an easy way to grow blue-green iron sulfate crystals on a piece of wire and turn it into a ring.

For the past few months, I’ve done lots of experiments with iron sulfate. Most of the time, I grew individual crystals, but recently I became interested in crystallizing objects too. So I thought I’d try to make a crystal ring.

A popular way to crystallize stuff is to dip a pipe cleaner into a supersaturated borax solution and let the crystals form on the surface. I do have some borax, but borax is colorless and I don’t like dyeing my crystals. So I decided to do it the cooler way, using some basic chemistry.

Preparation

First, I prepared 60 ml of a green, saturated solution of iron sulfate. I already had some to start with. But either way, iron sulfate is straightforward to make – just react some steel wool with battery acid.  The steel wool dissolves into the acid, turning the solution green by the following chemical reaction:

Iron metal + Sulfuric acid –> Iron sulfate + Water

Be careful when handling strong acids. Also, it should be done outside, because the reaction produces explosive hydrogen gas.

With the solution done, I twisted a few inches of steel wire into a ring. Then, I wound the remaining wire around a pencil. After that I just suspended the ring into the solution.

Growing the iron sulfate crystals

The moment I dipped it inside, the surface of the wire started to fizz. This is because the iron sulfate solution contained some leftover acid, which reacted with the wire, producing even more iron sulfate and hydrogen gas.

But this was exactly my plan. You see, the green iron sulfate solution was already saturated beforehand. And now, this second reaction produced an excess of iron sulfate. The excess iron sulfate then had no choice but to crystallize out directly on the wire.

This is what the ring looks like after just 30 minutes:

After 7 hours:

Unlike normal crystal growing methods, this method is much faster because I’m actively concentrating the solution by generating excess iron sulfate, instead of passively waiting for the solution to evaporate.

After exactly 1 day:

By this time, the fizzing had completely stopped. This isn’t because all the acid had been used up; rather, it’s because the crystals have coated the wire so completely that its surface is no longer exposed to the acid. Consequently, the rate of growth also slows down.

Note that small, flaky crystals also started growing up the part of the wire above the solution. This is normal, just like how water “climbs up” a cloth suspended in it. As upper part of the wire touched the acid, it began reacting, forming very thin coat of tiny iron sulfate crystals.

I wanted some bigger individual crystals, so I waited another day.

Then, I took it out of solution and dried it on a piece of paper.

And it’s done.

Enjoy the pictures

I also took it out for a few pictures in the evening sun. My neighbor’s plants made for an excellent backdrop.

Looks quite magical.

As a disclaimer, you can’t make an actual ring with this. This is because of 2 reasons:

• Sulfuric acid is highly corrosive, so make sure to wipe it completely dry before wearing. And even if you dry it, iron sulfate crystals are still a mild irritant, so it’s bad for your skin. Good for taking pics, but you shouldn’t wear it for longer than a few minutes.
• The crystals are easily scratched, and will dissolve in water too.

But it’s a fun project, and you can definitely impress your friends with it. It’s a simple process, and you can make bigger ones as decorations. It is just as easy to crystallize other shapes, like stars, or even a tetrahedron.

Left in the open, the crystals will turn brown over time due to oxidation, so take in their ephemeral beauty while you can.

I had a lot of fun making it, and I hope you enjoyed the read too. If you’re interested in another easy (and safe) DIY crystal project, consider checking out my article on how to grow alum crystals here.

Thank you for reading, and as always, happy growing.