For a kinetic sculpture idea I’ve had for years, I need a goodly supply of iron filings (say, a pound or so)- but where do I go to buy them?
No, I ain’t making thermite, despite my sig. 
Also, I need to suspend them in a clear fluid (in which they won’t rust)- I’ve been thinking mineral oil. But will mineral oil hold the filings in suspension? They don’t need to have absolute neutral bouyancy, but I’d like for them to remain suspended for a while, at least.
Any ideas?
Get your filings at Edmund Scientific. No idea about fluids.
Would glycerine work? Or corn syrup?
In my freshman chem lab, we created (rather, attempted to create, because it was really tricky) a substance known as a ferrofluid. It involved synthesizing very fine iron+something else (it’s been a few years) particles. We’re talking on a scale of microns. They had to be just the right size so that they would stay in suspension (I forget what fluid we had them in) without settling to the bottom or clumping together. For the lucky few that got it to work, it was really cool–you could manipulate the fluid itself (not just the particles within it) with a magnet. I bet if you did a google search you could find some info on them.
For the filings, try your local brake shop: cutting the discs and drums produces a nice, fine, powdery amount of filings.
Be careful, they tend to have slivers which will get under your skin.
For a fluid, try a heavy silicone.
Enola got it right. Yes, the brake shop is the best place to get it.
Clean the iron filings with acetone, if you need to remove the small amount of grease / dirt in them.
Silicone oil is the best. You may also try a saturated salt solution (put salt into water to the point where u can’t dissolve salt anymore). Silicone oil is easy to color also - just add a drop of iodine.
The best way to suspend the filings would be by using a magnetic stirrer as there is no physical object to stirring the liquid.
If you give more info on what you want to do, I can give more info.
All the best
A brine solution would be one of the worst things you could do from a corrosion standpoint.
Do not use a magnetic stirrer for this. Iron filings and magnetic stirrers do not mix really well. All your filings will clump at the bottom. Even worse, the odds are you will magnetize the fillings so they will stay clumped together. Trust me, I did this by mistake once. :smack:
Looks like you can order Iron Filings here and that site also suggests suspending them in Karo Syrup for at least one type of experiment.
As for the filings look up “machine shop” in your phone book or internet yellow pages, find a local one, and give then a call. It will be free, all you want.
They would certainly stay suspended in a gel. Clear gelatin, clear jello, etc. Their are many thick shampoos that are pretty clear as well - and hair gels. Glycerin is quite viscous (thick) and clear. There may be a wax that suits your needs.
Good lick!
Helixtwice, you’re a tad late to be joining this conversation! But the point was already made that gels would be inappropriate for this use; since they are water based, the filings would rust.
You need a surfactant to stop the micron-sized particles of iron from clumping.
You can buy the ferrofluid from this site and others, along with plain iron filings if you want. Just search using ‘but ferrofluid’ and ‘buy iron filings’. A surfectant is a necessity to get ferrofluid properties. You can also find a toy store and buy a bunch of those toys that use a magnet to draw with iron filings. You could probably also toss steel wool into a blender to get some but they may come out kind of coarse.
ETA: This article provides an easy method of making your own. They recommend kerosene and oleic acid for the surfectant.
TriPolar, you forgot to actually link the article.
Very sorry. Busy making pork chops, which is only slightly more complicated than ferrofluid. Here is the article.
I have tried the method using ferric chloride and oleic acid, and I have to admit–it’s very, very difficult to get right. Out of a half-dozen tries, I only got one batch that was remotely acceptable. I ultimately bought the ferrofluid, which is far superior in consistency.
Maybe I would get better results if I had a magnetic stirrer. Then again, it’s magnetic so maybe not.
That said, I can try to give some advice in case anyone wants to try the method. Heck, PM me your address and I can send you a small sample of the oleic acid. The smallest quantity I could find was a gallon, and needless to say I didn’t use all of it.
I presented that as one example. Frankly I’d get iron filings, kerosene, and see if I could get lecithin to work as a surfectant. It’s probably tricky to get the right mix with the right size powder. But you’re right, the ferrofluid is inexpensive enough to just buy it. My first link provided a source for that.
Not that I would discourage anyone from experimenting, but I really doubt that iron filings will work. The particles you need are measured in nanometers, not micrometers.
Here’s a little demo of my own experimentation in the subject. And another one (that’s my most popular video… almost 300k hits!). I have plans for more advanced sculptures, but they’ve hit a bit of a snag.
FWIW, if anyone is willing to cover a bit of the cost, say $10/oz, I’m willing to sell small quantities of the “real stuff”. I paid $150 for a full liter of it a while back and don’t need all of that, either.
You can actually have quite a bit of fun with a few drops in a test tube, along with an isopropanol/water mixture. An ounce would be enough for dozens of tubes; enough to keep a classroom of kids entertained, for instance.
I was just using a recognizable term. But you can start with filings and grind them down to 1 micron size using various methods. I wasn’t aware that sub-micron size was needed for ferrofluid. I’m working on making magnetohydrodynamic fluids using aluminum right now. I can get down to 1 or 2 micron size and hope that will be sufficient.
What health and safety precautions do you need to take when working with largish quantities of nanometer sized particles?
With any particles that size you have to avoid breathing them, getting them in your eyes, nose, ears, or ingesting them in any way. Each substance has it’s own individual hazard based on toxicity. I always work outdoors or mix everything inside of a big plastic bag. Also look up the Tin Man. I think there’s a thread about that.