How high a vacuum for wax potting ?

[the great waldo]

Hi All
Just a quick question, how high a vacuum in in.hg. should I be using to wax strat pickups? I´m getting an awful lot of bubbling if I go much over 23in.hg

cheers all

Andrew

[Magnut]

It's up to you to decide how much. Usually a small amount of vacuum will work. As the entire coil is warm enough to melt the wax it will continue to fill the voids.

Not everyone absolutely pulls every bubble out. As long as the coils are secure then the purpose is served. Some do pull out every bubble out. It depends on your style, how much patience you have and how much you suck.

[the great waldo]

Hi Magnut

I was just wondering if the high vacuum was actually causing the wax to boil because of the vacuum. I know with silicon casting degassing causes it to swell by 400 %.

Thanks in advance

Andrew

[Magnut]

In this case the high vacuum does not have that effect on the wax. The many bubbles you see are just air. A coil wound more loosely will certianly bubble more. The high vacuum just gives the appearance of "boiling" since the air is coming out so quickly.

The first time you put a vacuum to the wax, the wax itself may have air dissolved in it and that may give the same appearance. After the first vacuuming that should go away.

[David King]

Experience dictates that you should listen to unpotted, conventionally potted and vacuum potted pickups to see which one actually sounds better. You might be willing to live with an occasional squeal to get a really great sounding pickup the rest of the time.

[the great waldo]

Hi David

I´ll be trying that on some pafs i´ll be making.

Regards

Andrew

[Possum]

...

What is this obsession with vacuum potting? Half an hour soak in wax will pot the coil solid, how much more solid does it really need to be?

[David Schwab]

Right, and PAFs were not potted anyway.

[LtKojak]

What is this obsession with vacuum potting? Half an hour soak in wax will pot the coil solid, how much more solid does it really need to be?

+ 1.

To The Great Waldo:

Overpotting kills the tone.

This is one of those occasions where the rule "less is more" applies wonderfully.

HTH,

[the great waldo]

Hi All

Thanks for the response. I have used the vacuum potting( i´ve got the vacuum pump for degassing silicon for my modelmaking hobby, so while i´ve got it I might as well use it) I have made some vintage style strat pickups over the last few weeks and have sold quite a few sets here in Vienna to some quite fussy players. I´m so far happy with the sound of what I have made. I have been making and repairing guitars since the late 70´s some may remember me when I had a workshop in the basement of the Rose Morris shop in Shaftsbury Ave. in London. I will certainly try the pickups without the potting, Most guy´s seem to over use the gain control on the metal style amps these days so the potting helps. I was as a kid brought up in Ealing around the corner from the marshall shop in Hanwell,the fun of hearing and feeling loud valve amps being tested out by the local players attracted me to the electric guitar. In my everyday experience the biggest influence on tone is the player and not the gear. Good player + crappy gear = good music Crappy player + good gear = crappy music. I hope this is not to much of a ramble, I´m also trying to get back to the sound of the early 60´s strats and 335´s that I had to repair. They were great yardsticks for how a guitar can sound in the hands of a good player. The rest is personal taste, thankfully everybody has different tastes, ít would be a boring world otherwise.

Cheers All a great and usefull forum

Andrew Mazurkiewicz

[Possum]

...

Well, don't OMIT the potting especially on strats, though I think maybe some years they didn't pot them at all in the 70's, not totally sure about that though. Fender potted their early strat stuff and potted it solid as a rock but you don't need vacuum to do that, just soak them for half an hour or so and its done. Some use a partial potting, in and out real quick. Fender at one point lacquer potted some stuff but it really doesn't penetrate very deeply and over years can kill the wire and the pickup.....

[guitician]

I'm rewinding a '74 StratPU now and I filled the spaces between the poles before I wind it. Seemed like an easy way to do it. After I wind it I'll just melt a little more wax on the coil and be done with the potting.

[David Schwab]

Fender at one point lacquer potted some stuff but it really doesn't penetrate very deeply and over years can kill the wire and the pickup.....

I think they still do the bass pickups that way, at least the ones I've seen.

[David King]

I suspect that the lacquer shrinks a lot as it off gasses and that might be part of the problem with those coils. Nitro is only 15-20% solids.

I think a better use for vacuum might be to help squeeze the excess wax out of the coil. I'd wrap a rope of paper towel around the hot coil and then stuff it into a small ziplok bag and draw the vacuum on the baggy somehow. Has anyone taken this approach? I wonder if that's what Fender was effectively doing with the twine on his tele pickups...

[StarryNight]

I thought Fender didn't pot their pickups in the early days
Was their a phase where they stopped and started pre CBS?

I've been recently wax potting because of requests from high gain players. They're a challenging bunch. They want bright, clear tone that cuts through without any microphonics (and alll the good stuff that comes with microphonics). They rarely play clean and some get very picky about their tone. I find it much easier to wind for vintage enthusiasts.