How do you do it?

[LtKojak]

Mmmmmhhhhhh....

If the coils get wet they may stay that way a long time, if they do water is conductive and will make your pickups literally sound like they are underwater. PUt them someplace warm and let them dry for a week or so.....

I don't think the coils got wet... I can see wax inside'em through the bobbin's holes. That was the whole point, to melt the wax that was sorrounding the coils; so when the wax started to melt, I've taken the p'up and put it over a paper towel and let it drip for a little while, then I've clean it with a soft rag with a little bit of alcohol and voila! Got a nice, clean and dry p'up. It didn't take longer than two minutes per p'up, so I don't think they got wet in the inside, they didn't have the time to replace the wax with the water, as the wax trapped inside didn't melt, it melt only in the outside.

An hour later I've measure'em and they seem to work. Their readings didn't change, so I'm assuming they work ok.

If I'm wrong, I'll tell you next week when I'll have time to put'em through their paces installing'em in a test guitar.

Stay tuned!

[Possum]

....

If the coils are potted solid you're probably ok, it depends on how they were potted and for how long, water is death to coils, why I don't use shellac potting anymore. alot of cheap pickups use a microcrystalline wax, it smells funny and is kinda gooey, anyway good luck....

[Joe Gwinn]

Oh man, putting in water was the wrong thing to do. If the coils get wet they may stay that way a long time, if they do water is conductive and will make your pickups literally sound like they are underwater. Put them someplace warm and let them dry for a week or so.....

One symptom if water does get into the winding is that the Extech LCR meter will report higher to way higher than normal AC resistance.

[Possum]

...

Yeah, thats the famous "underwater" tone, treble just disappears into the depths :-)

[chevalij]

Man, have you people ever heard of an oven? Every house I've ever been in has one. Pop the pickup onto a piece of paper towel, throw it on a tray and slap it in the oven at about 160 degrees F. Have a beer (Canadian option), watch a sitcom, remove pickup, wipe.

[David Schwab]

You do that with plastic bobbins as well? I'd think they would get pretty soft.

My oven doesn't even go that low... starts at 250.

[Ruel]

Or get you "if you dont already have one" a slow cooker that can get down as low as 140 to 150 degrees and do an 80/20 beeswax,paraffin wax mix, heat the wax to 150, drop the pickup in and let it get to the temp of the wax, take it out and wipe it off, this should remove all the excess and may take out some of the coils wax too.

IMO, this is the best way to do it.

[chevalij]

You do that with plastic bobbins as well? I'd think they would get pretty soft.

My oven doesn't even go that low... starts at 250.

Nope, bobbins get really warm, but don't melt. I don't think they'll start to soften till they hit about 220+. I have a new digital oven, starts at 160 so it's great for pre-heating pickups etc before I pot them.

[David Schwab]

Nope, bobbins get really warm, but don't melt. I don't think they'll start to soften till they hit about 220+. I have a new digital oven, starts at 160 so it's great for pre-heating pickups etc before I pot them.

Oh OK. I have a digital oven also that starts at 350, but you can get it down to 250.

I had thought about sticking pickups in the oven when I'm encapsulating them to get the epoxy to cure quickly, but I'm worried about marring the plastic shells.

Maybe I'll do a test. One hour sure beats 24.

[Joe Gwinn]

Oh OK. I have a digital oven also that starts at 350, but you can get it down to 250. I had thought about sticking pickups in the oven when I'm encapsulating them to get the epoxy to cure quickly, but I'm worried about marring the plastic shells.

Common thermoplastics will start to curl up and warp at 250 degrees F, even if the surface finish isn't affected.

In the late 1960s, I worked at RCA in the Plastics Lab as a summer intern. The standard temperature for curing epoxy et al was 180 F (82 C).

The rule of thumb is that curing time is cut in half for every 10 degrees C (not F) rise in temperature. If room temperature (22 C) takes 8 hours, then 82 C is (82-22)/10= 6 doublings away, and so will in theory take (8 hr)(2^-6)= 0.125 hr, or 7.5 minutes. It will take longer for all parts of the assembly to reach temperature, and so on, so the actual time will be tens of minutes, but still it's a big improvement.

Conversely, given that one must wait for everything to achieve temperature, a lower temperature may be no slower in practice.

The high-temperature cure was also stronger, even after sufficient time for a full cure had elapsed for the room temperature cure.

However, too high a cure temperature weakened the bond, the optimum temperature varying with the epoxy type and mix. The optimum was found experimentally.

[jonson]

epoxy cure

David I normally use the same method for epoxy castings in rubber as I do for polyurethane. Which is I stick the molds in the oven at about 250 for 20 to 30 mins. Pour in the resin and then I have a doored box (mdf) about 3feet tall x 2 x 2 which has 2 shelves at 1 foot spaceing with large holes drilled all over them and a 100 watt lightbulb in the bottom. Cureing takes about 30 mins and normally have no probs whatsoever.

[David Schwab]

Common thermoplastics will start to curl up and warp at 250 degrees F, even if the surface finish isn't affected.

That's what I was concerned about.

In the late 1960s, I worked at RCA in the Plastics Lab as a summer intern. The standard temperature for curing epoxy et al was 180 F (82 C).

The instructions that come with the epoxy say you can cure it at 65 degrees C (149 F) for one hour. I don't really have any way of getting them to that temperature in a controlled way. Maybe I can make a hot box with a light bulb in it.

Since it's winter here now, I stick them in a small box and sit them on the radiator over night.

Jonson, I have these pickups in plastic pickup shells which will deform at that temperature.

[jonson]

plastic covers.

Sorry David did not realise that, I thought you were casting in rubber from scratch. A light box can be very controlable via a dimmer switch or just plain bulb choice but also look at the crackable gel packs for hand warming from camping stores. These can be packed round a mold in such a way as to control where you want the heat.

[David Schwab]

Sorry David did not realise that, I thought you were casting in rubber from scratch. A light box can be very controlable via a dimmer switch or just plain bulb choice but also look at the crackable gel packs for hand warming from camping stores. These can be packed round a mold in such a way as to control where you want the heat.

That's a good idea, and it made me think of electric heating pads that are used in guitar making.

Initially I was going to make molds and cast my pickups, but the shielding method I use now would be too cumbersome trying to fit in a mold without it touching the sides. Just potting them with epoxy is tricky enough!

I think I might start molding parts though.

[greenfingers]

I think a good idea would be to get an Oven thermometer for melting the wax if your going to do it that way. The thermostat in oven's are notorious for not giving you the temperature you set it at. I got that information from Heaston Blumenthal. the worlds greatest chef