Where to Buy Ferro Fluid?

[Pete B]

Parts Express and several other speaker suppliers have ferro fluid in different
amounts for sale but I believe that it is all the same viscosity.
It would be great to find other sources so that there are know sources for low,
medium and high viscosity ferro fluid.

Anyone know of other sources?

 

[Retrovert]

This doesn't give you a supplier, but it might explain how to attack the problem.

I had looked into this many years ago when I had a ferrofluid tweeter dry out and I could not find a source in less than 55 gallon drum size.

The ferrofluid recipe is not complicated. The ingredients are:

(a) ferric oxide
(b) oil carrier, typically petroleum
(c) surfactants to reduce the surface tension and improve adherance to the structures being cooled, probably a detergent
(d) antioxidants​

The oil must have reasonably low volatility, else the heat in the voice coil will evaporate it, and must have thermal stability, so it won't polymerize. I suspect it is a generic refined petroleum oil like mineral oil. Vegetable oils with a high flash point, such as sunflower or safflower at about 500 degrees F, could be used, but even unsaturated oils will crosslink with heat and oxidation, and eventually go rancid. Bleh. Petroleum will also oxidize, hence the antioxidants which are commonly added to engine motor oil.

NB: water can be used as the carrier, but this promotes corrosion and would not be suitable for this purpose.

The viscosity is therefore likely adjusted simply by the amount of oil present.

The question, of course, is what kind of oil is in the original. You might be able to find out what oil was used. I suspect it is a lightweight mineral oil of some sort. Experiments might bear this out. If you know anyone with access to a mass spec you could determine this.

So, you might be able to adjust the viscosity to suit your application by adding additional mineral oil.

 

[musichal]

I have it on tap for free from my ferro faucet.

 

[jlovda]

This doesn't give you a supplier, but it might explain how to attack the problem.

I had looked into this many years ago when I had a ferrofluid tweeter dry out and I could not find a source in less than 55 gallon drum size.

The ferrofluid recipe is not complicated. The ingredients are:

(a) ferric oxide
(b) oil carrier, typically petroleum
(c) surfactants to reduce the surface tension and improve adherance to the structures being cooled, probably a detergent
(d) antioxidants​

The oil must have reasonably low volatility, else the heat in the voice coil will evaporate it, and must have thermal stability, so it won't polymerize. I suspect it is a generic refined petroleum oil like mineral oil. Vegetable oils with a high flash point, such as sunflower or safflower at about 500 degrees F, could be used, but even unsaturated oils will crosslink with heat and oxidation, and eventually go rancid. Bleh. Petroleum will also oxidize, hence the antioxidants which are commonly added to engine motor oil.

NB: water can be used as the carrier, but this promotes corrosion and would not be suitable for this purpose.

The viscosity is therefore likely adjusted simply by the amount of oil present.

The question, of course, is what kind of oil is in the original. You might be able to find out what oil was used. I suspect it is a lightweight mineral oil of some sort. Experiments might bear this out. If you know anyone with access to a mass spec you could determine this.

So, you might be able to adjust the viscosity to suit your application by adding additional mineral oil.

A great conversation starter at a cocktail party.

 

[DOBIEGUY]

Pete
Unless you have a very specific application, the ferrofluid sold by Springfield Speakers on the big auction site is the way to go. Individual pre measured squeeze tubes remove the quess work.
The amount needed is in microliters.
I've used this in a few pairs of KEF tweeters successfully.
(no affiliation,just a satisfied user)

 

[smoke-libr8r]

Parts Express and several other speaker suppliers have ferro fluid in different
amounts for sale but I believe that it is all the same viscosity.
It would be great to find other sources so that there are know sources for low,
medium and high viscosity ferro fluid.

Anyone know of other sources?

Most of the places that sell ferrofluid carry the Ferrotec brand. I came to the same conclusion as you that it is all the same viscosity. I also concluded that it isn't viscous enough for many applications.

I was able to find higher viscosity ferrofluid after many, many hours of searching. I can't recall the names of the companies where I purchased it from. I remember that the thickest fluid that I found came from a manufacturer in Korea. I'd have to dig back through my records to find the company names. PM me if I don't reply to this tread in the next few days or so (I expect to be busy/distracted for the rest of the week).

 

[slimecity]

Hmmm

I went with the Ferrofluid from partsexpress to redo 4 KEF T33 tweeters.

This was after I thought that the viscosity may not have been enough - but also after several people on these forums said they used this OK.

I guess time may tell whether this was a good move or not. I simply couldnt find much of it, especially places that would deliver to NZ

 

[Pete B]

It would be VERY interesting to make some with synthetic motor oil, LOL!

 

[drumbum]

Maybe check into ferro fluid for Daiwa spinning reels.

 

[nfafan]

I have it on tap for free from my ferro faucet.

I found it at an old hardware "store" at a small rural airstrip, on the shelf next to rolls of flightline, gallon jugs of prop-wash, and left-handed wrenches.