Etching pickup covers

[liddokun]

I have a few old pick up covers that I want to try and etch.  Does anybody know if pickup covers are normally aluminum or stainless steel?  Would the ferric chloride etching process work on stainless steel?  I want to have a few nice designs on my humbuckers.

[ACS]

Normally going to be stainless.  Best bet for etching these is going to be nitric acid - nasty stuff.

Ferric Cl may work, but I'd suspect you're going to need plenty of time, temperature and concentration to get anything useful.  Get some offcuts and have a crack!!

[liddokun]

Yep, I have a spare cover I can test out. I'll put the results (for better of for worse) once I've finished.

[earthtonesaudio]

Stainless really?  I would have thought nickel or brass.

[ACS]

I thought that was usually just plating?

Gotta admit, I've never actually chopped one up to find out... 

How old are the covers in question?

[MarcoMike]

pay attention with those.... if they are something-plated, then if you etch the "coating layer" the metal exposed will probably oxydize and turn into rust or similar...
if they are stainless steel nitric acid is not really the way to go, as it will just passivate the metal, but this may be a nice looking result! also chloridric/muriatic acid will do more or less the same, turning the metal mat. you may be able to get a reflecting/non-reflecting image... seems quite nice!

[liddokun]

I guess I messed up huh?  It etched alright, but I didn't mask the edges properly, and in some parts it ate through all the way.  But this might be useful for maybe relicing perhaps? I left it in the ferric chloride over night.

[DavidRavenMoon]

Good covers are nickel silver.  Not so good covers are nickel or chrome plated brass.  Brass covers don't sound as good as nickel silver.  Seth Lover (the guy who invented the humbucker) initially wanted stainless steel covers, but settled for nickel silver.

[liddokun]

that's interesting. Thanks for the info.

[earthtonesaudio]

If the pickup cover was ferrous (steel, iron, etc) it would tend to re-shape the magnetic field, which can be a good thing.  Some people put steel plates on the back of pickups to focus the field upward toward the strings.  That can give higher output if you do it right.

[DavidRavenMoon]

If the pickup cover was ferrous (steel, iron, etc) it would tend to re-shape the magnetic field, which can be a good thing.  Some people put steel plates on the back of pickups to focus the field upward toward the strings.  That can give higher output if you do it right.

If the cover were ferrous, it would absorb all your magnet's field and you would get little to no sound.  You can try this out and see.  The reason why a nonferrous cover, like brass, would affect the tone is because it is more conductive than nickel silver (which interestingly is white brass), and any conductor in the presence of magnetic field will create a current flowing on its surface.  This is called an eddy current, because it swirls around like eddies in water.  These currents produce their own magnetic fields, which oppose the field from the main magnet. The highs are always the first to go because of impedance, so you get a dull tone.  This also applies to base plates on humbuckers.  You are correct that you can use this for tone shaping, but not with ferrous metals.

The steel pate on the bottom of a Tele pickup is slightly different because on that type of pickup, the poles are magnets.  So the steel plate sticks to the bottom of the magnets and acts to focus the magnetic field back up to the strings.  it also increases the inductance of the pickup.

With a humbucker, the bar magnet connects to the poles on both coils, so if you were to connect a piece of steel across the two coil's poles you would short out the magnetic field.

[Boprikov]

Stainless steel is non-magnetic. This was new to me, when i learned that from another pickup discussion.

[DavidRavenMoon]

Stainless steel is non-magnetic. This was new to me, when i learned that from another pickup discussion.

It all depends on the type of Stanless Steel. 

Most stainless steel is austenitic, which is usually non-magnetic, but can be paramagnetic, which is like regular steel. 

Then there is Ferritic stainless steels.  These are ferromagnetic, which is to say they are like ordinary steel, and are used in soft magnetic applications, such as pole pieces on pickups.  Barden uses stainless steel blades, and Bill lawrence uses stainless steel poles on some of his pickups.

Yet another type, Martensitic stainless steel, can exhibit permanent magnetic properties if magnetized in the hardened condition.

So try a few stainless steel things, like rulers and kitchen utensils, and flatware.  Magnets stick to some of it, but not the rest.