Magnet "aging": what the dickens IS it?

[Mark Hammer]

I've seen ad copy where manufacturers will talk about "magnet aging" as important in the tone of their pickups. The underlying assumption is that the desirable tones of older vintage pickups are, at least, partly related to the properties of the magnets used, and that magnets change over time.

So far so good. I have no quarrel with that. Hard to imagine anything being exactly the same today as it was 50 years ago, including magnets. And I fully understand that things also happen to coils over time, as well as to the magnet wire available in any given era, so magnets are never the whole story.

But then a couple of things got me thinking. I had always naively assumed that rod magnets started out life as magnets, and never gave it much thought until about 25 years ago when I visited the Evans pickup facility. I dropped in to score a couple of sets of polepieces from them, and was surprised to see Rod Evans pick up a bunch from a bin, stick them in what appeared to be a large electro-magnet, flick a switch for a couple of seconds, and then hand them to me "charged". Until then, I didn't know that stage happened.

Flash forward two and a half decades, and Monday I took receipt of some A3 and A5 rods purchased from one of the members here, and it came MY turn to charge them with some larger neodymiums. Charged one up and went "Nah, not strong enough yet".

Hold up at second base, there! Alnicos can be charged at LESS than their maximum strength.

So, without wishing to disparage the idea of "magnet aging" (and I think the notion is legit), and without wishing to extricate industrial secrets out of anyone, should I simply assume that what manufacturers of new pickups mean by "aging" is not anything to detract from a fully-charged magnet (in a manner analogous to "relic-ing" a normal nice guitar finish), but rather a very particular sort of under-charging of rods/bars so as to mimic what would happen to them after 40-50 years of being leaned up against amps?

And if so, does that imply that the various grades of alnico can mimic "aged" ones of a higher grade? I.E., if I charge my A3s to their max, does that put them sort of on par with A5s or A4s that have withered a little, or are there properties of those rods entirely distinct from that?

[big_teee]

The Aged thing is just more BS and fancy name for a weaker magnet.
De-Gaussed.
It sounds fancier and more polished to say "PAF Like", with "A2 Aged Magnets".
Instead of the same ole Humbucker with china made Half Charged A2 Magnets.
Later,

[marku52]

I.E., if I charge my A3s to their max, does that put them sort of on par with A5s or A4s that have withered a little, or are there properties of those rods entirely distinct from that?

You might take a look at the Alnico Grades in a Humbucker discussion, we are taking about this exactly. I think based on my limited understanding is, sort of. You could undercharge a stronger magnet to match the field strength, but there are other differences that may influence the tone beyond that.

Also, Alnico does lose charge over time, apparently at the rate of a percent or so per year. So compound that for 50 years or so, and you might see something significant. I haven't seen enough really old pups to tell whether this effect is meaninful or not.

[salvarsan]

Technical stuff

According to this article, Alnico alloys (except A3 which has no cobalt) form two different crystals unless annealed in a magnetic field to promote oriented columnar crystals, i.e., are anisotropic instead of more randomly oriented. The crystals differ in their distributions of iron+cobalt and nickel+aluminum, and each has a different balance of magnet strength and coercivity.

Aging an isotropic alnico magnet weakens the low-coercivity crystals so that the magnet, while weaker, has also stabilized at the strength of the high-coercivity crystals. This is technically not the same as partially charging a magnet, but is yet another way of reliably getting the results you want.

This suggests that for Alnico magnets (A5-7, A8, A9) that are annealed and grown oriented to an axis (anisotropic), aging by heat is less effective than under-magnetization.

[salvarsan]

Also, Alnico does lose charge over time, apparently at the rate of a percent or so per year. So compound that for 50 years or so, and you might see something significant.

Sometimes, it's the mileage as much as the years.

Short A2 slugs in a pickup (DeArmond) self-demagnetize from proximity while long slugs (as are in Rickenbacker Toasters) hold up very well.

Any pickup stored close to something strongly magnetic is at risk of demagnetization.

[belwar]

... when I visited the Evans pickup facility. I dropped in to score a couple of sets of polepieces from them, and was surprised to see Rod Evans pick up a bunch from a bin, stick them in what appeared to be a large electro-magnet, flick a switch for a couple of seconds, and then hand them to me "charged". Until then, I didn't know that stage happened.

As a side note, I bought his winder off of him about a year and a half ago. Had fish and chips with the guy in Victoria. Rod was a super niceguy who knew what he was talking about.

I have the great memmories of my dad charging alnico rods for our pickups when I was a kid. He had this metal tube (aluminum I think) when he put the magnets in. The tube had 12 gauge wire wraped around it. He'd then pop the hood of his car and touch the start and end of the wire to the car battery for a half second and BAM. Fully charged alnico. Im surpised he's alive.

[kleuck]

Alnico when properly magnetized and far as i know loses a few percent the first year, then something like 2% during a hundred years, so aging of magnets looks like fancy urban legend.
Anyway, each type of alnico has to be charged to a precise level to be stable trough the years, so it's possible that some old magnets got weaker after 10 or 20 years.
I don't know how manufacturers can make weaker magnets without shortening their lives, degaussed in the same magnetic field ?
Alnico III is not as stable as the other variant though.

[Mark Hammer]

So I am largely correct in assuming that "aging" involves strategic undercharging as opposed to something imposed on a fully charged alnico magnet?

[belwar]

So I am largely correct in assuming that "aging" involves strategic undercharging as opposed to something imposed on a fully charged alnico magnet?

^ Correct

[frankfalbo]

So I am largely correct in assuming that "aging" involves strategic undercharging as opposed to something imposed on a fully charged alnico magnet?

^ Correct

No this is not correct in our case. Our processes are not mine to divulge, but I think Seymour has referred to Dun-Aging in such a way that full charge, then controlled alteration of the charge is representative of time lapse aging, more so than undercharging. And the differences between old and new pickup magnets are usually not uniform.

As an extreme example, I had an old JB that sounded "sweet". Turns out the magnet lost more charge on the treble side than on the bass side. It also varied along the edge, but much more on the slug side than the screw side. This was not likely due to player's wear, but banging around someone's pickup drawer, probably with some ceramic inmates. Either way it was part of the pickup's character. I charged it (partially to debunk the "JB's have changed" myth) and it almost took full charge but maintained a little variety on the treble side slugs. After recharge it basically sounds like any new JB. Now we make an Antiquity JB. All of the awesome, none of the inconsistency!

[belwar]

Ok, let me elaborate on my "correct" statement...

To MOST people, it is simply means "partially demagnetize".

Even in your case, while it is highly controlled, it is still a partial demagnetization - correct?

[frankfalbo]

Yeah but re-read Mark's statement. I thought he was saying the opposite; to not fully charge at the onset.

[big_teee]

Yeah but re-read Mark's statement. I thought he was saying the opposite; to not fully charge at the onset.

S.D. I'm sure has all kind of Machines to Gauss and De-Gauss with.
A simple way is to use weaker magnets to charge with.
This gives a uniform weaker charge. I don't know what the long term longevity of the magnets will be.
The problem I've had with the full charge, then weaken them, is I can't keep the magnets uniform across the entire magnet.
Maybe you guys have an easy way that I don't know about.
Later,

[belwar]

with some practice, this works very well

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[Mark Hammer]

First off, thanks for all the comments so far.

Second, let me emphasize once again, I am not prying around for anybody's "secret". I'm just trying to understand roughly what people mean when they talk about it. So please exercise all the self-restraint you want in dancing around details.

Third, Frank's comment gives all of this a productive quarter twist by reminding us that what happens, or what can happen, to a pickup over time is not merely a matter of what might be true of a single magnet rod in isolation. So, what I might try to do with undercharging some A5s is not exactly the same thing as what might happen to a set of them in the same pickup, or to a bar, over time. Everything in context.