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Vintage threads from the first ten years

Re: Superglue & shellac potting?

5/7/2006 8:23 PM
Ken	Re: Superglue & shellac potting? I know on shellac cans there is a 'shelf life' stamp - shellac is only good for a short while, and after that it goes bad and may never dry at all. I think the stuff is only good for a year or so after the actual manufacture date. Ken

5/7/2006 8:30 PM
rf	Dave, When you did use shellac, was that all you did to the pickup? In other words, is it necessary to do like Rick Turner and seal it up with epoxy (or possibly a quick dip in wax)?

5/7/2006 8:47 PM
Ken	Maybe the pickup had to 'bake' until dry amd then the epoxy sealed the shellac from any further moisture. I know that shellac is a substance damaged by moisture, for example wet glasses left on shellacked tabletops leave permanent white rings (and angry wives). I'm going to have to try this out, now I'm curious. Ken

5/7/2006 11:56 PM
rf	Ken, You're definitely right about the shelf life of shellac. I believe the rule of thumb is that if you pour a bit on a piece of glass and it's not dry within five minutes it should be tossed. Also, shellac varies in its water resistance depending on its age and the amount of wax in it. Older shellac is less water resistant as is waxy shellac. I'm not sure how much wax is in the canned shellac you find at hardware stores (that's what Turner said he uses) , but I seem to remember that can I used had a milky appearance before stirring -- could've been wax or could've been something else they add. Of course, if you're sealing with epoxy, all of this probably doesn't matter. And some sort of seal is probably necessary anyway. Shellac dissolves in alcohol soit probably needs some sort of protection against those drunken, sweaty guitarists. As for baking -- leave the oven door open a crack. It should provide enough ventilation. Good luck.

5/7/2006 11:56 PM

Ken,

You're definitely right about the shelf life of shellac. I believe the rule of thumb is that if you pour a bit on a piece of glass and it's not dry within five minutes it should be tossed.

Also, shellac varies in its water resistance depending on its age and the amount of wax in it. Older shellac is less water resistant as is waxy shellac. I'm not sure how much wax is in the canned shellac you find at hardware stores (that's what Turner said he uses) , but I seem to remember that can I used had a milky appearance before stirring -- could've been wax or could've been something else they add.

Of course, if you're sealing with epoxy, all of this probably doesn't matter. And some sort of seal is probably necessary anyway. Shellac dissolves in alcohol soit probably needs some sort of protection against those drunken, sweaty guitarists.

As for baking -- leave the oven door open a crack. It should provide enough ventilation.

Good luck.

5/8/2006 3:27 AM
Dave Stephens	when I did use shellac I didn't use it straight, that would be crazy, I cut it with alcohol. I didn't know shellac had a shelf life and that might be a problem, but its so unpredictable its just not worth using in a commercial application for me. If I had my way I wouldn't pot any pickup but, there's always some guy playing some big ass amp in his bedroom with his volume on ten and his guitar a foot away from the speaker grille who will complain that the pickup is "defective." Thats actually happened to me. These guys who vacuum pot and totally soak the coil so nothing will ever move or be microphonic for the next two thousand years, they like what they do, I don't, I do it my way, whatever works for you and your customers and the type of music they play is fine. Apples and oranges.....

5/8/2006 3:27 AM

Dave Stephens

when I did use shellac I didn't use it straight, that would be crazy, I cut it with alcohol. I didn't know shellac had a shelf life and that might be a problem, but its so unpredictable its just not worth using in a commercial application for me. If I had my way I wouldn't pot any pickup but, there's always some guy playing some big ass amp in his bedroom with his volume on ten and his guitar a foot away from the speaker grille who will complain that the pickup is "defective." Thats actually happened to me. These guys who vacuum pot and totally soak the coil so nothing will ever move or be microphonic for the next two thousand years, they like what they do, I don't, I do it my way, whatever works for you and your customers and the type of music they play is fine. Apples and oranges.....

5/8/2006 8:42 AM
Mark Hammer	While wax "wants" to harden, shellac doesn't necessarily want to, and anything that inhibits curing will prouce problems. Sadly, the outside layer inhibits curing of the inside by preventing evaporation of the stuff in the shellac that allows it to cure. What hasn't been discussed here is the possibility or alternative of potting "halfway". When I buy french fries at the chip-wagon outside work, the woman always asks customers "Salt and vinegar halfway?", because she knows that salt and vinegar sprinkled from the top of the cardboard chip container will concentrate to much at the top and not penetrate down far enough to flavour the fries at the bottom. So why not pot "halfway" where the innner turns can be potted and cured easily and effectively and continute the winding from there? It may invove a solder joint on the coil, but if it gets you a rock-solid potting as a result, where's the problem?

5/8/2006 8:42 AM

Mark Hammer

While wax "wants" to harden, shellac doesn't necessarily want to, and anything that inhibits curing will prouce problems. Sadly, the outside layer inhibits curing of the inside by preventing evaporation of the stuff in the shellac that allows it to cure.

What hasn't been discussed here is the possibility or alternative of potting "halfway". When I buy french fries at the chip-wagon outside work, the woman always asks customers "Salt and vinegar halfway?", because she knows that salt and vinegar sprinkled from the top of the cardboard chip container will concentrate to much at the top and not penetrate down far enough to flavour the fries at the bottom.

So why not pot "halfway" where the innner turns can be potted and cured easily and effectively and continute the winding from there? It may invove a solder joint on the coil, but if it gets you a rock-solid potting as a result, where's the problem?

5/8/2006 7:02 AM

Joe Gwinn

On 5/8/2006 5:56 AM, rf said:

quote:
"You're definitely right about the shelf life of shellac. I believe the rule of thumb is that if you pour a bit on a piece of glass and it's not dry within five minutes it should be tossed."

I think that shellac lasts longer than a year if the can is kept well-closed, which means that one uses a piece of wood and a mallet to ensure that the lid is fully seated. It's also useful, albeit obsessive, to mark on the lid where the can's side seam is, and use this mark to ensure that the lid is always replaced in the original orientation. I learned this trick in a plastics lab in the late 1960s.

quote:
"Also, shellac varies in its water resistance depending on its age and the amount of wax in it. Older shellac is less water resistant as is waxy shellac. I'm not sure how much wax is in the canned shellac you find at hardware stores (that's what Turner said he uses) , but I seem to remember that can I used had a milky appearance before stirring -- could've been wax or could've been something else they add."

The wax is there naturally. One can buy dewaxed shellac.

quote:
"Of course, if you're sealing with epoxy, all of this probably doesn't matter. And some sort of seal is probably necessary anyway. Shellac dissolves in alcohol so it probably needs some sort of protection against those drunken, sweaty guitarists."

If the epoxy is applied too soon, it will ensure that the shellac never dries. Shellac is actually quite waterproof. The water rings are cosmetic.

As I recall, at least one person on the forum is using vinyl sanding sealer to pot pickup coils, having switched from shellac. The sanding sealer would remain flexible, unlike shellac.

quote:
"As for baking -- leave the oven door open a crack. It should provide enough ventilation."

A slow bake at low heat (100 F) should drive the alcohol out of even the most tightly wound coil, given the high vapor pressure of alcohol. A crude wooden box with a 50-watt or 100-watt lamp ought to work. Choose lamp size so the desired temperature is achieved. Higher temperatures are faster, but the limit on temperature will be bobbin warpage.

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