I recently discovered rheoscopic fluid which is used to visualize the subtle currents in liquid. It works similar to dropping dye into the fluid to highlight currents, but rheoscopic fluid will never mix! Below is couple clips of my first batch.
Also, here is the video that started my pursuit:
How does this magical substance work? Well, to paraphrase Wikipedia, there are crystal flakes that align with the direction of shear when in motion. These aligned flakes reflect light toward the observer. Once the fluid stops moving, the flakes take on a random orientation and light is again diffused. Of course, Wikipedia gave no hint to the actual ingredient... I searched for a few good hours trying to figure out how this stuff works. Turns out it's something of a trade secret, it would seem...
...Next is some history I discovered during my quest for the secret, but you can skip to step 2 if you're dying for the details.
Step 1: History
Wikipedia was a dead end and also lacked any history on the fluid. However, I remembered the name of the video I saw was 'Kalliroscope' so I looked it up. The wiki article linked it to the works of an artist named Paul Matisse. After prolonged investigation, I was able to dig up only one photo of him and an amazing creation. He built a table with a large rotary disc of rheoscopic fluid. As you turn it, a blue hurricane like structure appears in the table. It also turned out that the kalliroscope in the video was produced by Matisse in a limited run and are quite valuable now.
Rheoscopic fluid was also used in the past by educators and engineers. These days computers are predominately used to run simulations of airfoils and fluid dynamics, but before that models had to be built and tested. One method was to take the object and submerse it in flowing rheoscopic fluid. I managed to find one video from the 1960's (@ 2:22 & 23:50 min mark) demonstrating flow instability:
A rare modern replica too:
But this form of art/science was largely lost after the 1960's. Only a few museums have displays and the limited places that sell rheoscopic fluid really don't say what it's made of.
Step 2: Secret Ingredients
After my long search, one video had 'mica powder' in the description. My wife was over my shoulder and said nonchalantly that it is used in makeup to give that sparkly appearance. It's also used in shampoo to give it that distinct shiny goo look. It's non-soluble with water which is why it doesn't mix. So I face-palmed myself for thinking it was some exotic substance and ordered white cosmetic mica powder from amazon: http://www.amazon.com/Shimmer-Powder-Cosmetic-Slice-Moon/dp/B008H3NJ4G/ref=sr_1_3?ie=UTF8&qid=1397076546&sr=8-3&keywords=mica+powder
You can also purchase different colors of mica. This opens up the possibility of, say, red mica against blue water. I chose white to begin with as it is very reflective and will appear to take on the color of the liquid.
It was only 1oz for $9, but it went WAY farther than I expected. You could use half an oz on a 10 gallon aquarium and have nearly the same results as Paul Matisse's table.
However, mica is not the only mundane source of rheoscopic fluid particulate. If you can acquire very fine aluminium powder, it will duplicate the mica's appearance pound for pound. You can even produce your own aluminum powder with a coffee bean grinder, foil and ear plugs. Inhalation and ingestion of the powder is dangerous though, and the grinder will only be good for aluminum. I won't rule it out though for future projects as it may be cheaper in the long run and a respirator/gloves will mitigate the danger. Video link: https://www.youtube.com/watch?v=phMgqT6EsYc
Yet another way is to use silver calligraphy ink. If you happen to have some, it's a good alternative. You can use an eye-dropper to transfer the ink out of it's bottle. If not on hand or at a nearby store, I would just order some mica powder.
Ultimately, the cosmetic mica powder seems to be the best bang-for-your-buck and requires little effort.
*Update* Finely ground graphite seems to show similar properties. It might be the cheapest of the bunch, but it's naturally dark appearance may be an issue. It should not be handled directly; use gloves and a mask or respirator just like the aluminum method.
As for the working fluid the powder is suspended in, I use ordinary water! It works fine even if it isn't what Matisse used. After examining the label on an original kalliroscope in ebay, I discovered he used Tetrachloroethylene. It's on the EPA's hot list and is a chlorofluorocarbon + solvent. User Starphire tells me that it was selected due to it's low boiling point. This allowed convection to be seen when the solution was heated. It's also not flammable like other low boiling point liquids, but it's toxic. However, the visual difference in motion is minuscule and you won't notice unless you heat it (plus water is cheap)!
Step 3: Ratios and Additives
Simply adding a drop or two of food coloring per liter will give you great colors without diminishing the effect. You don't want to make it too dark a shade or it may block out light from reaching down into fluid. If you do make a darker fluid, you will need to add more mica to offset the occluded water. You can see in the photos that the plain white mica shines very bright, but is can be clouded substantially with (red) food coloring if used liberally. I am working on a ratio for darker mixtures and will update if I succeed.
Have some neglected high-lighters around? You can use them to add a vibrant florescent glow. I used some needle-nose pliers to remove the end-cap of the high-lighter. This revealed the ink well, which is just a squishy cotton like cylinder. Squeezing the ink well over your bottle of water will cause drops of high-lighter to fall in (as photos show). It looks very bright just in ambient light, but that wasn't enough. I exposed the mix to a UV flashlight and it created an interesting effect. Instead of the mica shining near the surface, the fluid seemed to glow from within and blocked by the mica. In other words, it was inverted in appearance like a negative picture film. The comparison picture shows it somewhat, but doesn't really do it justice. **special thanks to users Gravityisweak and Rpotts2 for the idea**
User Bpark1000 suggested adding some rubbing alcohol or dish soap to the fluid. This will prevent anything from growing in your container over time. I've been putting some dish soap in mine to test and it seems to be none-the-worse for it.
It's really that simple! Maybe it's just because of all research I had to do, but I expected it to be harder to get something this interesting.
*Note/Update: I tried using baby oil for a more viscous rheoscopic fluid and it didn't work. Oil based liquids seem to repel the mica powder. This causes it to form a layer between the jar and liquid. If you want to make the fluid more thick/viscous, you can mix in clear corn syrup to the water until you achieve the desired consistency. However, this seems to make the fluid really resist moving and makes for less spectacular results. Still, it retains a nice pearly shampoo like appearance and might be useful for something.
**Note/Update: Turns out the corn syrup/water mix was actually useful! User Gravityisweak brought up the idea of adding magnetic particles to the fluid and seeing what happens. Well, as fate would have it, I had a magnetic viewer filled with corn syrup/water I made a while back (added pics). You see, the magnetic particles are just tiny pieces of steel wool I cut up with scissors. The thick fluid suspends them for a long time. The added mica traces little paths as the steel wool bits move about. In retrospect, I would use less mica and wool for better visibility. Here is a link to the mag viewer 'ible (remember, corn syrup and water is what I used in lieu of oil):https://www.instructables.com/id/3D-Magnetic-Field-Viewer/
***Note: A lot of people have suggested using glycerin or Elmer's gel glue to thicken the fluid, but I haven't tested it yet. If you test it, please give us the results in the comments below!
Step 4: Easy Viewer
Step 5: Final Thoughts
So what can you do with it?
*You can use it in a science fair project to show convection currents or aerodynamics with this lost technique.
*Make a toy for the kids or desk at the office.
*Incorporate it in a prop for a costume or movie.
*Make a killer coffee table like this guy below:
* Update: below is a simple table that most anyone can build in a day or two! Check it out:
I have some other ideas too that I am working on. If you enjoyed this instructable, stay in touch for more. I'd love to hear ideas, suggestions, and answer questions! Have fun!