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Pivotal Health

Hazel and David Croucher

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MAGNET POWER IN MAGNETIC THERAPY


This page covers:

How it used to be: why magnets used to be very weak

Electromagnets, and how modern static magnets came to be invented

How it is now: magnets today; the qualities of magnetic materials

How can I tell good magnets from bad?


HOW IT WAS THEN

If you just want to know how to choose the right magnet, skip this section.

The problem of power

While magnets have been known for at least 2500 years, they were very weak. Metallic iron, nickel and cobalt, or an alloy from them, could become a magnet naturally or by stroking with a lodestone.  Lodestones are natural magnets composed of a particular kind of Magnetite crystal.

It does seem likely that some people gained healing through using such magnets - there were some logical thinkers then, just as much as there are today.  Most people who wrote the texts that later copyists thought good enough to keep had plenty of intelligence.  My guess is that a few people were particularly sensitive to the magnetic fields, and maybe had conditions that respond most readily to magnotherapy, such as arthritis.  But healers didn’t know much, if anything, about how it worked and usually put down the help to the supposed magical properties of magnets.

We have to come to the practical use of electricity to begin to make progress towards more powerful — and more effective — magnets.

Powerful electromagnets are essentially a nineteenth century invention.  They are at the heart of dynamos, generators and electric motors and they powered the Electric Age.  The magnetic fields they generated were huge compared to anything previously known and they captured the public imagination, being a popular science and comedy feature of Vaudeville and the Music Halls.

Electromagnets are still the best way to generate a very large magnetic field.  In medical use magnetic therapy in hospitals uses powerful electromagnetic machines, and Magnetic Resonance Imaging equipment (MRI) uses the strongest magnetic fields. Even more powerful are the huge electromagnets which pick up tonnes of scrap steel at a time.  The ongoing search for atomic fusion power is based on enclosing the nuclear fusion reaction inside enormously powerful electromagnetic fields.

Iron Magnets.  When a coil of wire has an electric current passing through it, the coil becomes a magnet, with the highest flux (magnetic strength) inside the coil.  A piece of iron or steel placed in the coil will become a magnet, and if it is heated then cooled while the electromagnet stays on, the iron will remain a powerful magnet even when it is taken out.

What actually happens is this.  The iron (or other magnetic material) is composed of groups of millions of molecules called domains.  These are normally separate crystals in the iron, each of which can become a tiny magnet.  Usually, they are weakly magnetized in random directions, so there is no overall magnetic effect.  The whole lump becomes an effective magnet when a lot of the domains - or better still, nearly all - are magnetized in the same direction.

When the iron is placed in a strong magnetic field and heated above a certain temperature, the domains remagnetize in the direction of the field they are in.  If the iron is then cooled while the field is still active, the piece of iron becomes a permanent magnet.  Magnetic strength drops over time for a variety of reasons, as domains randomise again.  Common reasons are banging the iron or dropping it, the influence of other magnets and heating the iron to near the temperature needed to make it in the beginning.

This is the origin of the modern ‘permanent’ magnet (doesn’t lose the magnetism when the current is switched off), also called a ‘static’ magnet (not needing a moving current). The earliest strong magnets were of various iron alloys (called steels), and by the 1920s they were a common product.  The mental image of a strong magnet even today is the comic cartoon of a little boy holding out a horseshoe-shaped steel magnet as big as himself and attracting iron objects to fly towards him!

HOW IT IS NOW

Not until the 1940s did the research into magnetisable materials get a real boost. Basic research into atomic and molecular structure and magnetic domains led to a better understanding of the nature of materials.  This led to more accurate prediction of how alloys might behave, so trials on hundreds of alloys began to find useful magnetic materials.  

Advances in mineralogy, refining and metallurgy made the rarer elements for alloys more affordable, and now we have many good permanent magnet types commonly available. Low-power ferrite and plastic-with-ferrite-dust are the cheap-and-cheerful end.  Other ceramics (magnetic pottery, if you like) and alloys from rare earths like samarium and neodymium make excellent high-power, long-lasting magnets.  For magnetic therapy, neodymium and samarium cobalt are really the only sensible choice.  For magneto-hydrodynamics, where weight is not such a consideration, strontium ceramics are good, too, and they’re cheaper.

HOW GOOD IS THIS MAGNET?

This is a quick summary of the properties and usefulness of each type of magnet commonly in use today.  Five new magnetic materials have relegated older iron and steel magnets into history.  For the uses I’m concerned with — therapy and magnetohydrodynamics — I’ve omitted several kinds of static magnet because either they lose their power quickly or they have other disadvantages for ordinary use, and so they’re rarely seen today.  The order below is by strength and it’s a practical rather than a scientific one.

Plastic >> Ferrite >> Strontium Ceramic >> Samarium Cobalt >> Neodymium

         WEAK            >>>>           STRONG                >>>>            EXTRA-STRONG

Plastic magnets

The good:    Cheap, flexible — the ‘fridge magnet.
The bad:      Very weak, magnetism fades away quite quickly.

Plastic magnets are simply magnet powder used as the filler in a flexible plastic which is set in a strong magnetic field.  They’re very versatile and are ideal for magnetic ‘sticky notes’ such as fridge magnets. But they lose their magnetism quite quickly.  Now you know why older fridge magnets tend to fall off when you slam the door!

Ferrite magnets  

The good:   Cheap.
The bad:     Weak, magnetism fades away from shocks or after a few years; brittle.

Cheap ferrite magnets are  a ceramic including some ferrite .  They are brittle, so they chip and break easily. They’re more powerful than plastic magnets, though — there’s more ferrite in them — so they make better fridge magnets and they have a lot of uses in appliances and gadgets which aren’t expected to last for long.  They’re the cheapest kind of magnet and are common in toys and short-life gadgets (like cheaply-made magnetic therapy products!)  We’ve seen them occasionally in $1000 magnetic mattress covers, which is unforgivable when you consider the low power and short useful life at such a high price.  Very few more dollars would have bought long-life magnets!

Extra:  A new type of magnet is the haematite bead or ring.  These are a polished, dull metallic grey stone - just like real haematite - with quite a strong magnetic flux.  Despite the name, they are actually made of ferrite - real haematite can’t be magnetized.  They look good and wear well but will be rather brittle.  I’d expect their magnetic strength to decline fairly fast, but not as fast as fridge-magnet ferrite.  Seems a great idea for jewellery and toys as long as you don’t expect much therapy!

Strontium ceramics

are by far the best of the ceramic magnets - the ultimate ferrite.  

The good:  Fairly inexpensive; powerful; very long-lasting.  Bioflow uses them in its fuel and water conditioners and gives a lifetime guarantee with good reason.
The bad:     Heavy for the power compared to those discussed below, and brittle - so can chip and break when dropped and should have a protective case.

They’re fairly cheap, they’re weatherproof and they last almost forever.  They are the static magnet of choice where high power is needed and weight isn’t important.  They are maybe three times as strong as ferrite for the weight, and cost much more.  

I’ve found one maker quoting these magnets as losing 2% of their power every 50 years, so they’ll outlast you!  They would take about 600 years to fall to half power.

Samarium Cobalt

magnets have a lot going for them.  

The good:   Very powerful and keep working in bad conditions like salt water and at very high temperatures.  They’re corrosion-proof and easy to shape.
The bad:     Expensive and chip easily - they’re brittle.

They’re powerful for their size and keep their most of their magnetic strength at quite high temperatures (eg, in boiling water).  They’re also long-lasting, keeping most of their power for centuries and are totally corrosion-proof in most conditions, including seawater and most acids.  

So, when a powerful magnet is needed for extreme conditions, they are the first choice. For magnetic therapy, they are better than anything except neodymium and have one advantage over that material: they don’t need protecting from rust.  The disadvantages are that they’re nearly twice the bulk and weight for the power, and they’re very expensive.  And — unlike 20 years ago — neodymium’s a lot cheaper.

Neodymium magnets

are the tops overall for therapy.  

The good:   Immensely powerful for the weight and size.  All reputable and most other magnetic therapy manufacturers use them.
The bad:     Need to be protected from rusting; fairly expensive.

‘Neodymium’ or ‘neo’ is  the usual term for an iron-neodymium-boron alloy, often shortened to FeNdB.  It can take a stronger magnetic flux than any other commercial material. Now the price has come down to something more affordable, neodymium’s bang-per-gram makes it the ideal choice where you want light weight and tremendous power. They’ve become vital today for computer hard drives, compact loudspeakers and a huge range of other applications — including therapy to match the hospital machines, if enough power and flux changing are used.

For the size, typical neodymium magnets are over 100 times as powerful as a lodestone, 20 times the power of cheap ferrite and half as powerful again or more than samarium cobalt. Not bad!  Neodymium magnets keep their magnetic flux nearly as well as strontium ceramics — according to one maker’s website, they’re quoted as losing about 5% of their magnetic strength every 20 years, so they will still have over half power 250 years after manufacture.

There’s a downside, though.  They rust like crazy — especially when kept damp and salty (like in the sea, or on a sweaty wrist!).  That’s because both the iron and the neodymium in the alloy are very reactive with oxygen, especially when there’s salt around.  So all neodymium magnets need some protection from air and water.  The best ones are triple plated with copper and nickel, then maybe covered with gold or a synthetic coating like tough epoxy paint or PVC.  And they are usually encapsulated as well, to avoid damage to the coatings.

If you can get round the rust problem — and that’s no problem to a careful magnet maker — neodymium is the one to go for where weight is an issue, like in a wristband. Just beware of those therapy bangles with the magnets embedded in the inside and only a light nickel plating for protection.  Skin acids soon strip it off, then the magnets rust, swell and drop out in chunks!


HOW CAN I TELL GOOD MAGNETS FROM BAD?

As magnets are often hidden, and cheap ferrite looks very similar to strontium ceramic, the best way to identify which magnetic material you have is to ask, or look at a specification.  You’d be lucky to get an answer, though — people who sell the poor stuff don’t advertise it as rubbish!  Don’t despair; there are a few visible tests and pointers.

1)  In the UK, copper coins made since 1991 have some iron in them; in the USA, pennies are iron-cored.  So, you can touch, say, a one penny coin to each magnet you’re checking and compare the pull on the coin for each magnet.  Try dangling a string of pennies from the magnet.  The more pennies it can hold up before the last one refuses to stick, the stronger the magnet. Anything steel, like a bunch of keys or some large ball bearings, will do the same job. Remember that quoting a magnetic strength is not helpful, because there are so many ways to describe magnetic power and dodgy sellers know all the tricks to confuse and confound you!  The pull on an iron object, though, is a simple and reliable comparative test.

2)  Neodymium magnets are easy to tell from most others: they have such fantastic power for the size.  Samarium cobalt magnets look quite like plated neodymium. They’re nearly as strong and just as acceptable, if a little bulkier for the power and more expensive.  And they don’t rust.

3)  The plating quality on a neodymium magnet is all-important if you want the magnet to last.  It’s best to cover it with something really corrosion-proof, like a shell or case made of stainless steel or plastic.  Otherwise, plan for a short lifespan before death-by-rust.  

4)  The same applies to bangle and bracelet materials.  Many are made from plated copper, brass or — worst of all — zinc-base metal.  The plating will quickly erode if you have strong skin acid.  Then the bangle will make your skin itch, while the magnets rot and drop out.  A rusting magnet will lose power as its metal content goes.  If this sounds despairing, it isn’t —  stainless steel and titanium bangles are easy to find and rotproof.

The Bioflow torc design used to be made of brass with a heavy chrome plating, then gold. Once the gold had been rubbed off, some people’s skin acid could get through the chrome in under two years; other people had no corrosion in six years.  We now use nickel-free stainless steel to avoid the problem completely.  All Bioflow magnets are encapsulated to give a long, corrosion-free life.


CHOOSING THE RIGHT MAGNET

We will concentrate on magnets for therapy and for fuel conditioning, because that’s what we sell. There’s quite a lot to say, so... time to start a new page.   Go to Evidence and Trials or Fuel Saving.


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Magnotherapy IN ACTION