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Alnico 4 - exact composition and electromagnetic specs decoded

by vaughn skow January 17, 2023 5 min read

Okay guitar gang, maybe I'm just crazy, okay, I am crazy, but I think this is HUGE!  But first, Just in case you have not yet done so, go back and read my last FIVE (!!) blogs decoding alnico:

The LowDown on AlNiCo Magnets

The Mystical Magical Qualities of Alnico III

Alnico II Properties - The musical Magnet

Qualities of Alnico V magnets - The Magnet that ROCKS!

Alnico 4, 8, 5DG, 5-unoriented, and other oddballs

So, I've heard a lot of hype about Alnico 4 (Alnico IIII) for quite a while now, some fairly reputable pickup makers even go so far as to claim it's the TRUE holy ,grail of humbucker tone.  And, I actually saw a forum where someone claimed to see all the magnet purchase orders from the 1950's ... and according to this dude, Gibson ordered almost ENTIRELY alnico 4 (A4) magnets in the 50's, but he did NOT provide any of the actual orders, or any other proof.  Until I actually SEE these purchase orders for myself, I'm going to consider this story to be pure hogwash.  Why would someone make up something like that?  Not sure, unless it's one of the couple of makers that tout A4, hummm.

What is Alnico 4 decoded exact composition

So, my experience:

A few years back, when I FIRST started hearing about A4 ... interesting that we ONLY started to hear about it in about 2010, isn't it?  We have known of the widespread use of Alnico 3, Alnico 2, and Alnico 5 (listed from weakest to strongest) since about 1947!

Again I say Hummmm ... A Mystery Is Afoot!

So, if you want to, do what I did... it's VERY informing!!!  Or just read along, but seriously, it's soooo strange!  Start with a simple search for alnico composition charts, Interesting isn't it?  EVERY SINGLE CHART leaves OUT alnico 4!  There are hundreds of charts from magnet manufacturers, physics labs, industrial design groups, and yes ... MANY from electric guitar pickup makers and even a BUNCH that were posted on forums.  And nope, no A4 anywhere to be found.  They ALL simply skips from 3 to 5:

Alnico composition decoded 1 2 3 4 5 8

If it were JUST this particular (very good) chart, that would mean nearly nothing, but it isn't.  It's all of them.  But I kept digging.  How about a very direct search for alnico 4 composition?  That should CERTAINLY get us a bunch of charts and numbers, right?  Nope! All you find is some "tone" comparisons from ... those pickup makers that brag about A4.  That's it!  By this point I thought I'd hit a dead-end and went to sleep perplexed.  Did alnico 4 even EXIST for real??  The next morning I decided to start going to the websites of the worlds actual magnet MANUFACTURERS, there are not that many of them, it's pretty specialized stuff!  I dug deep but I kept coming to dead ends, even the actual plants that make magnets didn't seem to offer alnico.  What??  But than I hit the site of industrial magnet manufacturer Arnold Magnetic Technologies.  And, once again I dug deep, REALLY deep. Guess what? I found A4!  (hold your applause)  Not anywhere with all the OTHER alnico magnet formulas that folks actually use and have used for many decades, but I investigated their "resources" page and BINGO!  There it was, a Material SDS, NOT an actual offering of A4, but rather the safety data sheet (actually a booklet) that is required for ALL raw materials, so folks will know EXACTLY what's in the things they are working with, in case any special safety precautions need to be taken.  These are a very, very important part of the manufacturing biz, you literally can NOT sell any raw material in the US or the "western world" without a Material SDS.  If some idiot were to EAT the darn stuff or something like that, they need to know EXACTLY what he ate, and how to deal with it, medically.  So, HERE is the alnico 4 SDS, it's a Adobe Acrobat file, you'll need to download, and look up section 3.2 : Mixture.

Yep, there IS finally a precise mixture for alnico 4, but not so fast!  Unlike all the OTHER alnico mixtures, A4 doesn't list exact VALUES of Aluminum, Nickel, Cobalt, and Iron, no, it lists a RANGE of values! 

This was worth a call to Arnold, as gfar as I can tell, the world's only A4 manufacturer!  It took a while, but I found a salesman who knew EXACTLY what the story was on A4.  It was called for by manufacturers who wanted a magnet as strong or stronger than A3, but even less expensive.  The specs called for a magnet with "approximately" the electromagnetic values of A3, but at an even LOWER cost than A3, which you remember actually has ZERO Cobalt.  So a compromise was made: A mixture that contained lots of nickel, the least expensive element of AlNiCo, a decent amount of aluminum, and not much, but just a touch of cobalt, ... but within a RANGE that would reflect what raw materials the manufacturer was able to get cheap or already had some of left over.  But wait, there's more!  It contains zero copper (which is fairly expensive) or tin, making it the ONLY alnico mixture to NOT include copper!!! It's not listed on any of the comparison charts because there are no exact specs. Whew. 

So what EXACTLY is alnico 4?

It's an alnico magnet with ONE design goal: Be Inexpensive; it's composition reflects whatever the manufacturer has available and wants to throw in, within a rather broad range!  And so, I made a complete chart, the FIRST EVER that compares the composition and electromagnetic values of alnico 4, right along side of all the other alnico grades. 

For the first time EVER,ere it is:

Alnico 4 comparison chart - the first ever

Arnold also provided me with the MINIMUM acceptable electromagnetic properties of it's A4 mixture, but remember, there is no actual value because the mixture has no precise amounts of the raw elements! Look closely, A4 has minimum specs about the same as our old cheap friend, alnico III  BUT, of course those are the MINIMUM specs, at the top end amounts of Cobalt and Nickle, the values would be somewhere between A2 and A5.

So what exactly IS Alnico 4? The Take-Away?

It's ... a crap shoot!  It MIGHT be similar to A3 ... or A2 ... or even close to A5!  Depends on what the manufacturer had on-hand on that particular production day.

Holy grail?  Magical?  I think not.  Most decidedly not.

And this, ladies and Gents, brings this EPIC 6-part deep dive into Alnico magnets to a conclusion.  I hope y'all appreciate the amount of work that went into this series, especially this section on Alnico 4!  Man, I need a Jacuzzi bath and a shoulder massage now, and distant vision?  Ah, it's over rated anyway, who needs it.

Next, we'll start an all new adventure.

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