Potting

[Paulkstadden]

This may seem like a silly question, but since I want to know as much as I can, and I've never heard anyone directly address this, I'll ask anyway. Other than eliminating microphonic feedback, does potting affect the tone of a pickup? I imagine there may be some harmonics that aren't present anymore once a pickup is potted, but I've never heard anyone say anything on it. Also, I've heard that epoxy potting does not penetrate the coils, and therefore does not stop microphonic feedback. Is this true? Still, there are people who either do not pot, use parrafin/beeswax, or epoxy. Are there other ways of eliminating microphonic feedback without potting?

Possum, I read on your site that the set you made for Jake E. Lee is not wax potted. Is there a reason for this? I'm very curious!

[Sock Puppet]

Hi,

This list shows the dielectric constants of paraffin wax(2.1-2.5), beeswax(2.7-3.0) and cast epoxy resin (3.6):

http://www.clippercontrols.com/info/dielectric_constants.html

This implies that the inter-winding capacitance will increase by these factors which in turn will roll off some of the upper harmonics you mention.

I think you'll find most people here use something like an 80/20 mix of paraffin wax/beeswax for the low melting point (or beeswax alone).

Having said that, I remember posts on the old Ampage forum where someone was allegedly using wax crayons... though it could have been a wind-up:)

S.

[Spence]

Personally I only use paraffin wax unless I'm doing an early Fender replacement set with a mix of paraffin wax and black boot polish.

What is the dielectric constant for Cherry Blossom?

Anyone?

[Sock Puppet]

What is the dielectric constant for Cherry Blossom?

Anyone?

Dunno Spence, try the Doc Martens site.

What's the dielectric constant for lanolin, that well known wire drawing lubricant from Wales?

S.

[J S Moore]

I thiink the wax crayon bit was for real, it came up on the LP forum.

[Possum]

I don't pot any of my humbuckers, Jake's sound clip was done through a POD so he's not playing in front of 12 Marshall stacks on 10. I don't pot them because I mostly make PAF type pickups which were never potted, and most of my customers are blues guys who don't play stadium rock at deafening levels. If I did I would have to pot them....

[J S Moore]

Jimmy Page and Peter Green didn't seem to have a problem with un-potted pickups.

I do it either way, depending on what the customer wants.

[Sweetfinger]

I use primarily parrafin, which gets a bit of crayon/beeswax/candle wax in it due to repotting of other previously/poorly done pups.

It does change the tone slightly by rolling off a tiny bit of highs, but more importantly, some of the "grooviness" of vintage pickups comes from the fact that they ARE slightly microphonic, and potting/solidifying will certainly kill that aspect, so I won't pot a valuable vintage pickup unless it is really unusable at even low to moderate volumes.

Other things to change if you want to eliminate microphonics are the springs. On any rock guitar, I'll change the pickup springs to silicone surgical tubing. Make sure no steel wool bits or string ends are stuck to your pickups as well.

[Paulkstadden]

Wow, that's all excellent info! Does tension and/or type of wind (scatter versus perfectly lined machine wound wiring) affect microphonic feedback? Anything else that can be used for potting other than the traditional materials?

[Spence]

Dunno Spence, try the Doc Martens site.

What's the dielectric constant for lanolin, that well known wire drawing lubricant from Wales?

S.

Allergic to lanolin and had to give up the sheep shagging. However, for those who'd like to try it, always get the sheep on the edge of a cliff. ....they push back better !

[Joe Gwinn]

What's the dielectric constant for lanolin, that well known wire drawing lubricant from Wales?It's in the same range as paraffin wax and beeswax. It would probably make a good softener for potting waxes, and is very good at preventing corrosion.

On the matter of the dielectric constant of mixtures: The dielectric constant of a mixture of two substances A and B, whose dielectric constants are Ka and Kb respectively, is the weighted average by volume of the dielectric constants of the two substances.

For instance, take a potting wax consisting of 80% paraffin wax (Ka=2.1-2.5=2.3) and 20% beeswax (Kb=2.7-3.0=2.85):

Kab= 0.80(2.3) + 0.20(2.85)= 2.41= 2.4

This works even if one of the substances is air (K= 1.00), as is partly the case in unpotted pickups.

[David Schwab]

Speaking of paraffin wax and beeswax... there was a discussion over at the MIMF forum, where Clint Searcy did a photo essay on restoring some 1950's Le-Re pickups from a Finnish made Malmström lap steel.

The pickups had failed because the beeswax they were potted in caused corrosion that went all the way to the wire. It seems beeswax is acidic!

Should we be using that stuff?

I use potting epoxy myself.. but I'm not winding PAFs or Strat pickups.

[Joe Gwinn]

Speaking of paraffin wax and beeswax... there was a discussion over at the MIMF forum, where Clint Searcy did a photo essay on restoring some 1950's Le-Re pickups from a Finnish made Malmström lap steel.

The pickups had failed because the beeswax they were potted in caused corrosion that went all the way to the wire. It seems beeswax is acidic!

Should we be using that stuff?It may be a purity issue. No wax is acidic. Or an environment issue: where did this failed pickup live? maybe the problem was ingress of beer.

In any event, there must be millions of pickups potted with beeswax, and very few have failed.

I use potting epoxy myself.. but I'm not winding PAFs or Strat pickups.Epoxy works, but the danger with rigid potting is mismatches of temperature coefficients of expansion causing stresses large enough to break something. Humidity coefficients can also do this, although it's not likely to be a problem with pickups (which are physically small and largely made of impermeable strong materials).

[David Schwab]

It may be a purity issue. No wax is acidic. Or an environment issue: where did this failed pickup live? maybe the problem was ingress of beer.

That's not what I read when I looked up beeswax:

It is a tough wax formed from a mixture of several compounds including: hydrocarbons 14%, monoesters 35%, diesters 14%, triesters 3%, hydroxy monoesters 4%, hydroxy polyesters 8%, acid esters 1%, acid polyesters 2%, free acids 12%, free alcohols 1%, unidentified 6%

The main components of beeswax are palmitate, palmitoleate, hydroxypalmitate[1] and oleate esters of long-chain (30-32 carbons) aliphatic alcohols, with the ratio of triacontanylpalmitate CH3(CH2)29O-CO-(CH2)14CH3 to cerotic acid[2] CH3(CH2)24COOH, the two principal components, being 6:1.

The guitar was from Finland. Clint couldn't figure out what was causing the green corrosion all inside the pickup, and it even went past the paper tape and corroded the solder joints. When he melted out the wax it looked like this (see attached photo):

The pickups were sealed and filled with wax.

In any event, there must be millions of pickups potted with beeswax, and very few have failed.

This is true.

Epoxy works, but the danger with rigid potting is mismatches of temperature coefficients of expansion causing stresses large enough to break something. Humidity coefficients can also do this, although it's not likely to be a problem with pickups (which are physically small and largely made of impermeable strong materials).

There's also many pickups (and other circuits) out there potted in epoxy. I have a Hi-A pickup from 1972 which still works. :) I use epoxy specially made for encapsulating and potting ... not sure if it's different from "normal" epoxy. I get it from Mouser.

The last set of pickups I made I coated the coils with polyurethane after I wound them. I happened to have had a can and thought I'd give it a try.

[erikbojerik]

Or an environment issue: where did this failed pickup live? maybe the problem was ingress of beer.

Hehehe....Bruce Springsteen's old Esquire has a hole near the bottom of the body, so that Bruce's sweat can drain right on out.

[Paulkstadden]

David, what type of epoxy do you use? Mouser has 44 different types of epoxy!

[David Schwab]

David, what type of epoxy do you use? Mouser has 44 different types of epoxy!

It sure takes forever to locate parts in their catalog!

590-832B-375ML
MG Chemicals Epoxy C
Epoxy Compound

It's black. I didn't see that many epoxys. I think I was specifically looking for potting compound.

I found a bunch of things at Mouser that sure make my life easier. :)

[David Schwab]

Hehehe....Bruce Springsteen's old Esquire has a hole near the bottom of the body, so that Bruce's sweat can drain right on out.

Wasn't there an XLR jack there? I remember seeing it in an old photo.

[Paulkstadden]

That's excellent! I've been wanting to make an accurate copy of John Birch's Magnum, and now I can use an appropriate epoxy.

[David Schwab]

I'd love to see what the magnet structure is for that pickup. Gibson filed for a patent on the Iommi model, which is based on the Birch Magnum.

A lot of bass pickups are potted in epoxy, such as Bartolini, Q-Tuner, and Lane Poor. I think all three are cast in resin, and don't even use a shell the way EMG does.

I make no claims as to any sonic differences, but I just started potting some, and I have some that are un-potted, so I'll see how they compare.

My motivation is feedback suppression, and to make it real difficult to see inside the pickups! ;) Makes everything nice and solid.

[Joe Gwinn]

The guitar was from Finland. Clint couldn't figure out what was causing the green corrosion all inside the pickup, and it even went past the paper tape and corroded the solder joints. When he melted out the wax it looked like this (see attached photo): [lots of green stuff]. The pickups were sealed and filled with wax.I've never been in Finland, but I did live for a year in Stockholm, Sweden, across the water from Finland. It is more likely to be very dry than very wet - the climate reminded me of Maine. But I would guess that this pickup has to have been stored in very high humidity.

This [that there are millions of pickups potted with beeswax that nonetheless work] is true.There are acids, and there are acids. Rosin, used as a flux for soldering electronics (and pickup coils) also contains organic acids, and yet it is safe to leave the rosin on the soldered joint, even with #45 wire. It is the organic acids in rosin that allow it to work as a flux, removing the oxides from copper and tinned surfaces, allowing the solder to wet the now-clean metal surfaces.

That said, perhaps beeswax comes in grades, although I have never heard of such a thing.

There's also many pickups (and other circuits) out there potted in epoxy. I have a Hi-A pickup from 1972 which still works. :) I use epoxy specially made for encapsulating and potting ... not sure if it's different from "normal" epoxy. I get it from Mouser.Potting epoxies are thin enough to penetrate the winding, have solvents that won't destroy the wire enamel or bobbin, and don't change size enough to cause undue stresses upon hardening.

The last set of pickups I made I coated the coils with polyurethane after I wound them. I happened to have had a can and thought I'd give it a try.By "polyurethane", do you mean varnish, as for coating wood? This should work.

[David Schwab]

Potting epoxies are thin enough to penetrate the winding, have solvents that won't destroy the wire enamel or bobbin, and don't change size enough to cause undue stresses upon hardening.

Oh good... It was expensive enough!

By "polyurethane", do you mean varnish, as for coating wood? This should work.

Yes. I had a small can I was using on some wood, and figured I'd give it a try.
Seems to have worked fine.

Regarding the beeswax, the poster on the other forum assumed it was acidic, so I looked it up. But who knows what caused the corrosion. It was off that it went al the way through the wax to the coil. You would think the wax would prevent that kind of thing. :confused:

[Paulkstadden]

There's not much info available on the Birch Magnum. I've really tried hard to find out about it, too! John Carling says it uses a Cobalt Steel magnet (only described as "huge"), black epoxy potting, stainless steel covers, and the old ads say it has a 20k ohm resistance and a frequency response of 3,000-8,000 khz. The Gibson Iommi is based on the "Jaydee Special" which is in the bridge position of Iommi's Jaydee SG. Unfortunately, I've heard that John Diggins doesn't remember how he made it! J.T. Riboloff yanked the pickup from the guitar and took every measurement he could in preparation for production of the Gibson Iommi. I used to have a couple of them, really loved the sound they got. Great for hard rock! They, as far as I could tell, were epoxy potted, too. As soon as John Diggins gets the time and the tooling, I will order a P-90 size Magnum. Can't wait to get that into an SG!

As a matter of fact, that's the pickup that made me want to try my hand at winding. I'm still buying every tool I can get that will help me get closer to that goal. Also, since I'm just a newbie, I'm still trying to get as much info as I can before I start winding. Made some electronic stuff before without research first and ended up with hissing, popping, dry jointed garbage. Not doing that again! Thanks for everyone's info and advice, it's been excellent!

Oh, one more thing. If I epoxy pot a pickup, is there any way to take the pickup apart if I'd need to? I've heard that an epoxy potted pickup would be destroyed if it were taken apart.

[Sweetfinger]

It may be a purity issue. No wax is acidic. Or an environment issue: where did this failed pickup live? maybe the problem was ingress of beer.

In any event, there must be millions of pickups potted with beeswax, and very few have failed.

Whenever I see serious corrosion on a pickup, it is usually due to a celluloid pickguard that has deteriorated and outgassed corrosive fumes. Maybe those Malmstrom pups used celluloid bobbins- I couldn't find the thread referred to- but if celluloid went south inside the cover, I'd be surprised if there was anything metal LEFT inside!

[Spence]

You should be aware that the RoHS directives may exclude you from selling pickups potted with some compounds.
At my company we've gone green and have developed a high tech replacement for wax and epoxy compounds :

402

:smoke:

[David Schwab]

Whenever I see serious corrosion on a pickup, it is usually due to a celluloid pickguard that has deteriorated and outgassed corrosive fumes. Maybe those Malmstrom pups used celluloid bobbins- I couldn't find the thread referred to- but if celluloid went south inside the cover, I'd be surprised if there was anything metal LEFT inside!

I don't see how celluloid would cause corrosion on a plated brass cover and wires... celluloid is not much different from nitrocellulose lacquer. You'll notice only the metal parts have been affected.

Here's the bobbins. I don't know what they are made from, but they look intact. Of course I'm just going by the photos. I haven't seen the pickup in person. I'll ask Clint what he thinks the bobbins were made of.

[David Schwab]

The Gibson Iommi is based on the "Jaydee Special" which is in the bridge position of Iommi's Jaydee SG.

Oh that's right... I forgot about the Jaydee. I see the Jaydee has a Birch Magnum copy Diggins made at the neck. The bridge pickups looks quite interesting with dual rails. Those humbuckers are P-90 size!

http://www.iommi.com/equipment/images/jaydee_custom_sg_aka_no1_2.JPG

Oh, one more thing. If I epoxy pot a pickup, is there any way to take the pickup apart if I'd need to?

Nope. Do all your experimenting and testing prior to potting. I don't think epoxy potting the pickup will effect the tone as wax does. I'll let you know.. I'm potting a couple today.

I have disassembled an old broken Lawrence pickup potted in polyester resin. I ended up with a usable magnet and bobbins, but forget about the magnet wire!

Here's a photo of an EMG 81 taken apart.. same outcome.

[David Schwab]

You should be aware that the RoHS directives may exclude you from selling pickups potted with some compounds.
At my company we've gone green and have developed a high tech replacement for wax and epoxy compounds :
:

The epoxy I got from Mouser is RoHS compliant.

http://www.mouser.com/search/refine.aspx?Ntt=590-832B-375ML

However my solder is not! I'll have to cross that bridge when I get there.

What is that in the photo?

[Spence]

The epoxy I got from Mouser is RoHS compliant.

http://www.mouser.com/search/refine.aspx?Ntt=590-832B-375ML

However my solder is not! I'll have to cross that bridge when I get there.

What is that in the photo?


composte, good for potting. It was a joke Dave.

[David Schwab]

composte, good for potting. It was a joke Dave.

Ah! I couldn't tell from the photo... :D Potting... ha!

[Paulkstadden]

Actually, it's a Biflux in the neck. Diggins sent me a really good closeup of it (he's fabulously nice about that, he's sent me a lot of pics of his guitars in progress!) I'd always read that it was a Magnum, even reading it in a mag with an interview with Iommi. Then he sent me that pic, and there it was, "Biflux by John Birch" written on the cover. Presumably, they were all hand engraved, maybe even by Birch himself, but I don't know.

Yeah, the P-90 size makes it difficult to copy! Getting bobbins, covers, and baseplates is impossible without custom making them. Diggins just got the tooling in to make the P-90 sized copies and he is making a new copy of the old Jaydee guitar for Iommi! As soon as he can make a Magnum, I'm definitely ordering one! I will be taking as many readings as I can.

I'd love to know about your newly potted pickups. Any info I can get before making one, I'll take! Again, I've made stuff without researching first and ended up with crap. No more!

[David Schwab]

Actually, it's a Biflux in the neck. Diggins sent me a really good closeup of it (he's fabulously nice about that, he's sent me a lot of pics of his guitars in progress!) I'd always read that it was a Magnum, even reading it in a mag with an interview with Iommi. Then he sent me that pic, and there it was, "Biflux by John Birch" written on the cover. Presumably, they were all hand engraved, maybe even by Birch himself, but I don't know.

Ah, ok. On Iommi's page (http://www.iommi.com/equipment/jaydee_custom_sg_aka_no1.htm) it says:

The pickups are of different types, the bridge is a Jaydee special and the neck is a John Birch style Magnum X in a John Birch casing, though made by John Diggins.

I'm sure John knows what he made! John makes very nice basses.

I'd love to know about your newly potted pickups. Any info I can get before making one, I'll take! Again, I've made stuff without researching first and ended up with crap. No more!

They are bass pickups... soapbar humbuckers. I'm finished testing them, and now it's time to pot them. I'll be doing that tomorrow morning. You need a closed cover. Pour some epoxy in and place the guts on the pickup in it.

Here's one in the "test" bass. (it's covered in blue painters tape to protect the cover from scratches.)

[Paulkstadden]

The closed cover, that would explain why Gibson's Iommi pickup has the closed cover. Still, how would one do it with a cover that's got holes drilled in? Those old Magnums had the row of balance screws but were still epoxy potted, how'd Birch do it?

By the way, love the bass, looks like some nicely flamed maple on that top.

[Paulkstadden]

Actually, here's a nice shot from Jaydee's site. The writing can be seen on the neck pickup.

http://www.jaydeeguitars.com/images/iommi-sg/close-sg.jpg

[Sweetfinger]

I don't see how celluloid would cause corrosion on a plated brass cover and wires... celluloid is not much different from nitrocellulose lacquer. You'll notice only the metal parts have been affected.

Different enough in some cases. Look Here
http://aic.stanford.edu/jaic/articles/jaic30-02-003_3.html
and here
http://www.balisongcollector.com/celluloid.html
and some more
http://en.wikipedia.org/wiki/Celluloid
The effects of celluloid decomposition on metals are well known, and when you look at some of the compounds formed during decomposition, like nitric acid, it isn't hard to see how a brass cover or wiring can be eaten away. You should consider yourself lucky that the government has not seen fit to regulate old pickguards the same way it has regulated the storage of old nitrate film stock. You'd have to store all chunks of old funky binding, and pickguard in steel drums UNDER WATER!

[David Schwab]

The closed cover, that would explain why Gibson's Iommi pickup has the closed cover. Still, how would one do it with a cover that's got holes drilled in? Those old Magnums had the row of balance screws but were still epoxy potted, how'd Birch do it?

It can be done. Pick up a copy of Animal Magnetism for Musicians, written by the guy that makes Q-Tuner pickups (http://www.q-tuner.com/). He shows a bunch of bass pickup designs that are all cast in resin, and some have adjustable poles. You have to wax them so they don't stick!

Epoxy potting is messy work. I wouldn't want to bother with adjustable poles!

By the way, love the bass, looks like some nicely flamed maple on that top.

Thanks! I love that bass. I stopped using it for a while because I made the string spacing at the nut as wide as a P-bass, which was a bit much for a 5 string! So I removed the hardware and put them on my zebrawood bass.

Now I like the neck on the maple bass, so I'm making new pickups for it. It has a great tone. The two basses sound quite different.

[David Schwab]

You should consider yourself lucky that the government has not seen fit to regulate old pickguards the same way it has regulated the storage of old nitrate film stock. You'd have to store all chunks of old funky binding, and pickguard in steel drums UNDER WATER!

StewMac stopped carrying celluloid binding because it's flammable.

To this day most movie theaters still have the thick walls on the projection room, with the tiny hole for the projector (and a big steel door) because of the old explosion risk!

I see your point about the celluloid. But still the coil forms on those old pickups didn't look deteriorated. They certainly looked better than my old Mustang pickguard!

[Paulkstadden]

The book looks excellent. Amazon has it for cheap.
I love his wood pickup surrounds. And those pickups he makes look rather funky, too. I see the coils of wire, but what the heck are those things in the holes going through the pickup? Some sort of polepieces?

[David Schwab]

I see the coils of wire, but what the heck are those things in the holes going through the pickup? Some sort of polepieces?

Pole pieces. Hex (Allen) screws actually.

[Clint Searcy]

I don't see how celluloid would cause corrosion on a plated brass cover and wires... celluloid is not much different from nitrocellulose lacquer. You'll notice only the metal parts have been affected.

Here's the bobbins. I don't know what they are made from, but they look intact. Of course I'm just going by the photos. I haven't seen the pickup in person. I'll ask Clint what he thinks the bobbins were made of.

Hi folks,

I'm glad to see that my work has sparked some debate. I welcome any alternate points of view about the cause of the extensive corrosion found in both of these pickups. There have been some good suggestions mentioned here and I considered and rejected most of those as I worked to solve this mystery.
To best understand this case it's important to know that the coils inside these pickups were held in place with nothing but bees wax. All parts were totally submerged in wax. This allows us to rule out things such as beer or other liquids being spilled into the pickup. There’s no way it could have gotten that far into the wax. Plus, the wood in to bottom of the cavities is as clean as the day they were made. No stains or other evidence of spilling exists.
Celluloid deterioration is an interesting suggestion but the guitars have no celluloid parts and are 100% original. Also there is no damage to any of the other metal parts of the guitars so that can be excluded as well.
Salt air? Again, the pots, hook up wire and output jacks and other metal parts are all clean and corrosion free. Yet the parts inside the pickup covers that should have been protected from salt air by the wax were all heavily corroded.

It's also important to understand that this potting wax was not bought at the local Arts and Crafts store. This wax likely came straight out of the hive. In post war Finland there was no easy place to find parts and supplies. This information combined with several articles on the corrosive nature of natural bee’s wax all point me in this direction. There are two competing theories on why this happens. One states that the wax itself can have a high enough acid content to cause corrosion. The other suggests that the wax acts as fuel for Microbiologically Influenced Corrosion to occur.

Here are some interesting articles on the matter.

http://findarticles.com/p/articles/mi_go2568/is_200303/ai_n7473723

http://palimpsest.stanford.edu/byform/mailing-lists/cdl/2000/1313.html

https://metropolitanmuseum.org/Works_of_Art/objects_conservation/spring_2003/mixed.asp

Now, I'm not suggestion that everyone run out and replace all their wax. Clearly it seems that not all bees wax exhibits this trait. But working on these pickups has convinced me that the possibility is very real. I think it’s important to pass that information along.

[Joe Gwinn]

Hi folks,

I'm glad to see that my work has sparked some debate. I welcome any alternate points of view about the cause of the extensive corrosion found in both of these pickups. There have been some good suggestions mentioned here and I considered and rejected most of those as I worked to solve this mystery.
... So, it really is the beeswax.

Now, I'm not suggestion that everyone run out and replace all their wax. Clearly it seems that not all bees wax exhibits this trait. But working on these pickups has convinced me that the possibility is very real. I think it’s important to pass that information along.Nor is it common to use pure beeswax in pickups, and mixtures will vary.

[Clint Searcy]

Nor is it common to use pure beeswax in pickups, and mixtures will vary.

True, I would assume most are using the 80/20 mix you and I use. But those who restore old and odd pickups might find this information useful.

[David King]

Could someone have used acid core solder at some point inside these pickups, perhaps to solder the cases together?
I apologize in advance if this was already ruled out, I can't focus long enough to read 3 pages of posts.

[Clint Searcy]

Could someone have used acid core solder at some point inside these pickups, perhaps to solder the cases together?
I apologize in advance if this was already ruled out, I can't focus long enough to read 3 pages of posts.

I'm not sure that it was mentioned here David but I did think about that possibility. The problem is that these pickups were made using coils from surplus WWII military radio handsets. In other words, the person who soldered the covers together and soldered the volume pot and out put jack was not the same person who soldered the coil connections and as you can see in this picture the connections into the coil failed from corrosion.

http://i67.photobucket.com/albums/h300/searcystringworks/Pickups/malmstrom16.jpg

[Spence]

[QUOTE=Joe Gwinn;16642]So, it really is the beeswax.


QUOTE]


How do you know it's pur beeswax? Had it tested? Are we to assume that the bees producing this wax were drinking acid rain? The mystery deepens....

BTW, what's the coating on the coil wire and the lead-off wires? I suspect a chemical interaction here.

[Clint Searcy]

How do you know it's pur beeswax? Had it tested?

Nope, I'm working on the word of the manufacturer who claims it was bees wax.

Are we to assume that the bees producing this wax were drinking acid rain? The mystery deepens....

Ummm... well no. Why would we assume that?

BTW, what's the coating on the coil wire and the lead-off wires? I suspect a chemical interaction here.


I'm not entirely sure what insulation was used on the wires. If I had to guess I would suspect it to be Formvar. Can you think of an insulation that reacts so severally with bee’s wax? I would be very interested in learning more about that. But then that would not explain the corrosion all along the inside of the covers.

http://i67.photobucket.com/albums/h300/searcystringworks/Pickups/Final23.jpg

[David Schwab]

Are we to assume that the bees producing this wax were drinking acid rain?

Acids are a natural part of bees wax. I'd guess it helps prevent bacterial growth? If you think about what bees use wax for, that would make sense. :)

[Joe Gwinn]

Joe Gwinn: "So, it really is the beeswax."

How do you know it's pure beeswax? Had it tested? Are we to assume that the bees producing this wax were drinking acid rain? The mystery deepens....No, the bees are pissing in their wax.

Seriously, beeswax contains many anti-bacterial ingredients, just as does honey.

[Ruel]

Different enough in some cases. Look Here
http://aic.stanford.edu/jaic/articles/jaic30-02-003_3.html
and here
http://www.balisongcollector.com/celluloid.html
and some more
http://en.wikipedia.org/wiki/Celluloid
The effects of celluloid decomposition on metals are well known, and when you look at some of the compounds formed during decomposition, like nitric acid, it isn't hard to see how a brass cover or wiring can be eaten away. You should consider yourself lucky that the government has not seen fit to regulate old pickguards the same way it has regulated the storage of old nitrate film stock. You'd have to store all chunks of old funky binding, and pickguard in steel drums UNDER WATER!

Wow! I didn't realize balisong (Pilipino for fan knife) is now this big. A website dedicated to "balisong" collectors? Who would have thought?