Turbulent Flow Christmas Ornaments

This tutorial will introduce a method of making a Christmas ornament that is dynamic and mesmerizing to watch. By spinning a rheoscopic fluid in a clear ornament ball you will be able to see the turbulent flow of the fluid inside. "Rheoscopic" means to ability to "see fluid currents"; this is fascinating optical phenomena is achieved by using a special fluid that contains light reflecting particles that do not dissolve in solution.

This fluid mixture is one of those simple yet captivating phenomena like fire and magnetism that entertains children and adults alike.

Supplies

• Water (tap water works, distilled water is best)
• Rheoscopic concentrate (I used Pearl Swirl, but there are multiple options)
• Food colouring
• Clear, fillable Christmas ornaments (can be found at dollar stores and craft stores)
• Hot glue
• Coreless DC motor with drone rotor (like this)
• Electrical wire, heat shrink tube, switch, fuse, solder, 3V power supply

Step 1: Step 1: Mixing the Rheoscopic Fluid

In a container mix 1L of water, 1 tablespoon of rheoscopic concentrate and a couple drops of food colouring. As you begin to mix the solution you will see chaotic flows arise. For the best results I recommend boiling the water first (to remove dissolved air), I personally didn't do this but I think the final result would look better if you did.

Note that if the fluid is allowed to rest for several hours most of the light reflecting particles will settle at the bottom of the container. This isn't an issue as long as you scrap the very bottom of the container when you come back to stir it. I left my own mixture for several days and within 20 seconds of mixing the rheoscopic effect came back fully.

Step 2: Step 2: Methods to Agitate the Mixture

At this point it is clear that a stir rod works very well for stirring the mixture. But I encourage you to experiment with different methods as it is a lot of fun to watch the turbulent flows. Some ideas that were successful for me: dropping objects in the container, a magnetic stir plate (as found in chemistry classrooms/labs), a tube to blow air through, and placing the room temperature fluid on a hot surface (to visualize thermal convection currents).

But coming back to the objective of making Christmas ornaments with this fluid, I found the best method was to use a small DC motor to stir the mixture (after all who want to aggressively rattle ornaments)?

It may seem silly at first to put a DC motor inside a fluid, and while generally it is not a great idea, for short term applications (like the couple of weeks until Christmas) it will not lead to an immediate failure. As such we can submerge the motor directly in the fluid to agitate it. Nonetheless, the likely cause of failure will still be corrosion from electrolysis on the brushes. I will come back and update this when the motors do fail, so far they have been going for 48 hours with no problems. Using distilled water will decrease the chance of failure compared to regular tap water.

I came up with 2 different configurations:

1. Vibration motor (link)
2. Coreless motor (link)

The vibration motor is commonly used in mobile phones as a notification feature. By soldering thin wires are submerging the motor it can agitate the rheoscopic fluid, although the amplitude of agitation is small. The better performing motor was the coreless DC motor with drone rotor blade attached.

Furthermore, the coreless DC motors only has open holes at their base (which will be sealed with hot glue), the end of the motor that has the axle coming out tightly mates with a metal bushing, making it difficult for any water to ingress, thus further delaying the potential electrical failure.

Step 3: Step 3: Making the Ornaments

When the silver top of the clear, empty ornament is pulled off there will be two holes that the wires from the motor can be fed through (see pictures). I then tied a reef knot to temporarily secure the motor in place. To permanently secure the motor I applied hot glue to the base of the motor, do your best to fully cover the base of the motor as this is the most likely point that fluid will get inside the motor.

Before attaching the rotor blades you will need to bend them to fit through the neck of the ornament. I was able to bend mine without issue but in case yours is made of a brittle plastic you may want to heat them with a hot air gun first. Once bent, attach them to the motor (see pictures).

To transfer the fluid to the ornaments I found it easiest to use a plastic syringe but a funnel would work too. Remember to stir the mixture before filling the ornaments to ensure none of the particles have settled at the bottom of the container. Leave a little bit of air in the neck of the ornament as the motor will displace some of the fluid.

Fill the silver cap of the ornament around the motor with hot glue and quickly and firmly push it onto the neck of the ornament, ensuring that a waterproof seal is made between the surfaces.

Before proceeding to the next step ensure each ornament works by connecting the motor terminals to a 3V power source.

Step 4: Step 4: Finishing Touches

Now that the ornaments have been made there are a few final steps to make them ready to hang. Firstly cut 2 lengths of wire with openings every 30 centimetres or so, at each interval solder a connection to to the motor. I personally used some male-female connections (link) so that if one of the motors fails I can easily remove it without unsoldering everything. Add heat shrink tubing to insulate the solder joints, preventing short circuits. I also recommend connecting a fuse so that should one ornament fail the power supply will disconnect instead of melting the wires/damaging the power supply.

Finally I wrapped the wires connecting the ornaments with some tinsel (you could also use LED lights if you wish). Hook the wires up to a 3V power source and you have a chain of ornaments, ready to hang.

Suggested improvement:

• One improvement that I may add in the next version is instead of a fixed power supply I might try using a PWM driver to control the speed and direction of the motor. Personally I like the slower speeds for visualizing the fluid currents.

Comments

[acesaro]

Wonderfull idea! I'd add LED's inside it to a magic effect in the dark. Same concerns apply to do not let LED's lids touch the liquid!

[Ludvic]

Man your project it's awesome.but i have an ask for you..
how you made the animated preview for your instructables??

[PaulHaas]

I love your project. I basically had the same idea, but using a snow globe and a magnetic stirrer. A drop of dish detergent and its been two years and not bacteria grow yet.

[bpark1000]

You will have trouble with bacteria and algae growing in the ornament. You can prevent this by substituting about 30% alcohol for some of the water.
Regarding the motor corrosion problem, put the motor outside the ornament and have it turn a small magnet. Another magnet (ceramic magnet will not corrode) inside will spin (like magnetic stirrer).

[PieBaby89]

Congratulations!! This is truly a unique and one of a kind Christmas ornament, I absolutely love it and wish I have a set for my tree. Excellent win!

[Will Donaldson]

Thank you!

[RustedFriend]

I wonder if you'd get enough interesting flow from convection currents if you had a small heater inside it. Like say a resistive heater that you just plug into an empty spot on your Christmas light line. It would also be fairly simple to make a magnetic stirrer arrangement. Great project. I've been wanting to do something with rheoscopic fluid for a while and this is giving me ideas for some sort of visual stimulus that can live on my desk.

[Will Donaldson]

Yep! Thermal convection currents work with this fluid, I played around with some hot and cold mixtures but your idea of a resistive heater would be a good method too.
Edit: could also look into peltier plates

[rayj0007]

Nice effect! I had to look up what rheoscopic fluid was.

I don't know if rheoscopic fluid is effected by magnetism. If it is, this suggestion may not have any value.

A possible modification might be to a mechanism similar to a magnetic stirrer used in labs. Put a magnet in the fluid, seal the fluid in and mount a motor with another magnet outside the sealed fluid positioned so the magnetic fields are coupled. The spinning motor and magnet will result in the magnet in the fluid agitating the solution. Agitators of different shapes could be attached to the magnet.

Assuming the magnet in the fluid is adequately protected from damage by the fluid, the sealed fluid chamber should last until dropped :>) The motor/magnet assembly could use virtually any motor suitable to the task, and would be replaceable/interchangeable as desired.

Again, nice project. Thanks for sharing.
rayj0007

[Will Donaldson]

Yes, magnetic stir plates work (there are some videos on youtube). However for this application it was not viable as there is no flat surface in the ornament for the stir rod to spin on and it is difficult to mount the motor in a discrete way that preserves the traditional ornament

[mrmike83642]

Not sure how it would affect the rheoscopic fluid or change the desired
effect but if you used mineral oil instead of water it would help
prevent corrosion and reduce any chance of electrical failure.
Just a thought, and love the project.

[KNERD_UNO]

Distilled water would do the same (and be cheaper)./

[rachl009]

These look so cool!

[Karishma Kumar]

This is Awesome!!

[2403366]

i would of given a vote but it has things that we cant get from stores
and were in the world will we get that fluid thing ?

[Will Donaldson]

Hi, in the section called "Supplies" I list all the required parts. Most of the parts can be bought locally. There is a link to where you can buy rheoscopic concentrate online, alternatively there are lots of suppliers on Amazon. Some art supply or craft stores carry the fluid locally too.

[BlueFreckles]

What a cool effect! I could see it in some potion bottles for halloween.

[Will Donaldson]

Great idea!

[Arduino009]

Awesome. Definitely worth a vote. I'll be sure to try this out some time.

[jegatheesan.soundarapandian]

Amazing work......