The difference between a wax soak and vacuum potting.

[rhgwynn]

There you have it. I pulled these apart for the magnets to build a stacked bucker. Not too surprised at what I saw. You need a good vacuum to pull a wax core into the spaces between the poles - if that's what you want, of course. Also the ones with wax cores, that were vacuum potted, were much harder to pull apart, due to the higher concentration of wax actually in the body of the coil.

-Rob

[Mike Sulzer]

You need a good vacuum to pull a wax core into the spaces between the poles -

-Rob

When you create a low pressure at the exit of the bell jar, the air molecules fly out and the force of gravity pushes wax into the pickup. It is the kind of like when you dump water on the floor: the initial impact causes the water spread out, but gravity assures that the layer of water gets very thin on a level floor and goes everywhere. It is the second effect that pushes the wax into the pickup as the level of wax in the pot tries to settle to the lowest possible level.

[ScottA]

When you create a low pressure at the exit of the bell jar, the air molecules fly out and the force of gravity pushes wax into the pickup. It is the kind of like when you dump water on the floor: the initial impact causes the water spread out, but gravity assures that the layer of water gets very thin on a level floor and goes everywhere. It is the second effect that pushes the wax into the pickup as the level of wax in the pot tries to settle to the lowest possible level.

Gravity is acting on the system whether it's under vacuum or not. I would think the vacuum impregnation mechanism would have more to do with pressure gradients, surface tension and capillary action.

[rhgwynn]

You fellers are getting silly complicated. It blows my mind how I start simple threads and then they get complicated and over thought like crazy. It's pretty simple to me, because I'm a simple feller I guess. One bobbin shows a soak, the other two - I put'm in a jar of melted wax, tighten the lid that has a hole, and pump the air out with a brake bleeder. Bubbles fly up, every three minutes or so, I let the air back in and pump it out again. I do this two, maybe three times. Gravity may act on the coil regardless, but only up to a point (as demonstrated by the photo). Anyhow, if ya wants to get complicated - carry on

-Rob

[ScottA]

You fellers are getting silly complicated. It blows my mind how I start simple threads and then they get complicated and over thought like crazy. It's pretty simple to me, because I'm a simple feller I guess. One bobbin shows a soak, the other two - I put'm in a jar of melted wax, tighten the lid that has a hole, and pump the air out with a brake bleeder. Bubbles fly up, every three minutes or so, I let the air back in and pump it out again. I do this two, maybe three times. Gravity may act on the coil regardless, but only up to a point (as demonstrated by the photo). Anyhow, if ya wants to get complicated - carry on

-Rob

It's all about the physics.

[big_teee]

It's all about the physics.

I thought it was about potting pickups, and no squeal.

[ScottA]

I thought it was about potting pickups, and no squeal.

Yeah, that too.

But really, if you want to do something well and for the right reasons and with the right results, you have to understand what's going on at the fundamental level.

This stuff may sound obsessive, but it's really not. Potting, for example. The degree to which the wax impregnates the coil will directly effect the tone because it directly effects the distributed capacitance. When you wax pot, you displace air (with a dielectric constant close to unity) with a material with higher dielectric constant. If you want to have control over the tone of your pickups and you're wax potting then you need to have control over your potting process. As an engineer who has worked in some of the most advanced factories (semiconductor fabs) on some of the most advanced processes (Chemical Mechanical Polishing) on the planet, I can tell you from first hand experience that if you don't understand the fundamentals of your process, you have very little hope of really controlling it.

[rhgwynn]

It's all about the physics.

Nice save there Scott. Your original comment really made you seem like, uh, well... not nice :P

-Rob

[Mike Sulzer]

Gravity is acting on the system whether it's under vacuum or not. I would think the vacuum impregnation mechanism would have more to do with pressure gradients, surface tension and capillary action.

Yes, if you leave the pickup in the pot with the molten wax long enough, the wax will penetrate from gravity. This takes so long because the air has to escape, and this happens very slowly if the air in the pickup has to come out through the wax without a pressure difference. The pressure difference from the pump gets the air out quickly, and then the wax gets pushed in by gravity.

[rhgwynn]

Yeah, that too.

But really, if you want to do something well and for the right reasons and with the right results, you have to understand what's going on at the fundamental level.

This stuff may sound obsessive, but it's really not. Potting, for example. The degree to which the wax impregnates the coil will directly effect the tone because it directly effects the distributed capacitance. When you wax pot, you displace air (with a dielectric constant close to unity) with a material with higher dielectric constant. If you want to have control over the tone of your pickups and you're wax potting then you need to have control over your potting process. As an engineer who has worked in some of the most advanced factories (semiconductor fabs) on some of the most advanced processes (Chemical Mechanical Polishing) on the planet, I can tell you from first hand experience that if you don't understand the fundamentals of your process, you have very little hope of really controlling it.

I might go so far as to say, that this only really applies to those doing some crazy rough guesstimate method like mine. But those who are just soaking the pickups and timing it - have a pretty easy way of standardizing things. If they do it exactly the same (ratio, temp, time, depth, etc) every time; they can pretty much know just what to expect.

-Rob

[Mike Sulzer]

Nice save there Scott. Your original comment really made you seem like, uh, well... not nice :P

-Rob

I think you misunderstood him.

Why the hostility to physics? Here is a case where the correct principles are understandable with no math.

[ScottA]

Nice save there Scott. Your original comment really made you seem like, uh, well... not nice :P

-Rob

You saw that, huh?

I did type that out, but I thought better about posting it - I thought I had deleted it but it was below the visible part of the screen. That's why I edited it right away!

[ScottA]

Why the hostility to physics?

That's the gist of what my deleted part was about (but maybe a bit too pointed).

[rhgwynn]

That's the gist of what my deleted part was about (but maybe a bit too pointed).

Heh, not really hostile to it, actually enjoyed it quite a bit in high school; just never really went beyond that. I do enjoy a bit of learning but, quite often had trouble making intellectual connections with some instructors teaching styles. You could also say I enjoy a bit of that blissful ignorance, too; I like that ongoing sense of wonderment in life, not thinking about too much in the mathematical sense. Everyone's different, but I like the balance I've struck, for now.

-Rob

[ScottA]

Heh, not really hostile to it, actually enjoyed it quite a bit in high school; just never really went beyond that. I do enjoy a bit of learning but, quite often had trouble making intellectual connections with some instructors teaching styles. You could also say I enjoy a bit of that blissful ignorance, too; I like that ongoing sense of wonderment in life, not thinking about too much in the mathematical sense. Everyone's different, but I like the balance I've struck, for now.

-Rob

I had this thought the other day: Why do we say "reduced to a science"? We should say "elevated to a science".

Now before anyone brings it up I understand the concept of "reduction", but especially for a lay-person, I think the context of diminishment is strongly behind the use of this phrase.

I've worked in a series of fields that were viewed as "as much art as science" and have striven to do my part to elucidate what's going on inside the "black box".

I find the reaction of some people that you're "taking the fun out of it" when you do this to be odd. I think it is exactly the opposite. I find that generally when you answer a fundamental question, you raise a bunch more that are just as interesting. Plus, you make the job easier and more focused because now you know more exactly what you're looking at.

There's wonderment, fascination and satisfaction to discovering the physics underlying the behaviors you are observing, that's why we do it.