Are there any potential problems besides the safety warnings above? Yes. There is always a small risk that you could damage a pickup. If you have a particularly collectable instrument or a pickup that is of questionable construction don't do it. That being said, I have done very many of these over 15 years and have never damaged a single pickup.
What about removing the pickup covers? It is not neccessary to remove the metal pickup cover from a humbucker. It is easy to damage pickups by trying to take them apart bad idea! Be careful if you choose to remove your covers remove at your own risk! If you have a metal cover on your pickup - leave it on for the potting. Some pickups (especially older inexpensive models from Japan in the 70s) look like a regular Gibson humbucker but unlike the Gibson pickups the covers are not made to be removed. Most full-size humbuckers made in the 90s can have their cover removed.
If the coils are wrapped with tape do not try to remove it. Pot the pickups with the tape in place. Trying to remove it may damage your coils.
If a pickup is already potted in a hard plastic material (some older Ibanez models, Bartolini stacked humbuckers, and Select pickups come to mind) then you are out of luck do not try to remove a sealed plastic cover. Do not pot Lace sensors.
The plastic covers on Stratocaster single-coil pickups should be removed. These just slip off once the pickup is removed from the guitar. Some have tape around the coil, some do not. Leave the tape on if it is there.
Why not replace the pickups with new potted ones? Replacement pickups can cost $200 or more. Enough said! I had a newer model Epiphone and potted the pickups and an astonishing thing happened they actually sounded really good. Potting your existing pickups costs very little and can save you a lot of money if you like their sound. Many people are happy with the tone of one or more of their stock pickups and may not want to replace them. If you later sell the guitar, many potential buyers would rather have the "correct" pickups.
Instructions for potting a pickup
- Make a sketch of your wiring before you remove your pickups so that you can use it as a guideline to put your pickups back in later.
- Remove your pickup(s) from the guitar.
- Mark the pickups with a piece of tape on the wire if you cannot easily tell what position in the guitar each was removed from.  (Remember that markings on the bottom of the pickup may be difficult to see after the pickup has been potted.) Put the tape near the loose end of the wire, not near the pickup where it will become encased in wax when you dunk the pickup.
- Use a double boiler to melt the wax. I heat until it is only just hot enough that it completely melts (you can use a candy thermometer to determine the minimum temp, but I wing it). You will need to have enough wax melted to more than completely submerge the pickup. If you heat it without checking the temp, you run the risk of warping or melting your pickup. [Ed. The Fralin article at the StewMac website recommends 150 degrees F. I highly recommend a candy thermometer as the wax goes over 200 degrees suprisingly easily (though when it did it didn't damage some plastic-bobbin Tex Mex pickups I was potting). A candy thermometer will set you back a whole four bucks and is available at most grocery stores.]
- With a pair of pliers or tongs lower one pickup into the melted wax. Do not actually touch the coil windings with the pliers or tongs as doing so will almost certainly destroy your pickup. Grab the pickup by the tab used to mount it. [Ed. note. instead of tongs you could use pieces of stout string or picture hanging wire tied through each mounting hole. This ensures that you won't drop the pickup, splattering hot wax, or accidentally grab the coil windings with tongs or pliers. Tie something to the loose end of each string so it will hang outside the pot and not end up in the wax.]
- Leave the pickup submerged and jiggle it gently until no more air bubbles seem to be coming out of it. This takes a while (up to fifteen or twenty minutes) because the pickup has to heat up to the temperature of the wax around it before wax will adequately penetrate the coils. Move the pickup every few minutes to different angles to get the bubbles out. Try to avoid letting the pickup stick to the side of the double boiler.
- Remove the pickup and allow to dry and cool on a paper towel. Remember it is hot coming out of there! Let it cool naturally in room-temperature air don't try to speed up the cooling process. You may want to wipe the face off a little while the pickup is still warm because it is easier to clean. Getting wax off after it has fully cooled is a pain. Wipe off only the outside of a metal
humbucking cover or the top of the coil bobbins (where the pole pieces are) and not around the bottom or sides of the coil.
- Repeat the previous three steps for any remaining pickups. Work on one pickup at a time. Don't try to clean one pickup while soaking another. Pickups are expensive and each deserves your full attention throughout this process.
- After the pickups have cooled clean any excess wax out of the mounting holes and reinstall them in your guitar using the wiring diagram you made earlier.
You have now potted your pickups. Enjoy the benefits of less feedback and noise John Thornburg
Update: Here's a quick photo of the process. Last spring I potted some pickups and took a quick photo of my setup. The inner pot of the double boiler is a camp pot with a cover. When I'm done I just put the cover on and let it cool and it's sealed up until the next time I need to use it. I used two pounds of canning wax. I couldn't find any beeswax at WalMart so I went to the shoe department and got a 7 ounce jar of Kiwi "Camp Dry Beeswax Water Proofer." This is beeswax with a bit of lanolin mixed in and is about the consistency of a soft, moist paste. It mixed readily with the canning wax (parafin). This mixture seemed to work just about perfectly. You can see the nice golden hue in the photo and it even leaves your pickups smelling nice!
Note that the inner pot is suspended by loops of picture-hanging wire. This isn't as stable as it could be so you have to watch that the inner pot doesn't tilt to the side and spill melted wax into the water in the outer pot. Using an outer pot that is not too much larger than the inner pot helps in this respect this setup wouldn't work well if the outer pot was much wider.
I also used picture-hanging wire tied through one mounting hole on the pickup to handle the pickup without risking damaging the coils by grabbing them with tongs or pliers. I was able to shake the air out of the pickups just by gently jerking on the picture-hanging wire. I missed getting a picture of the free end of the picture-hanging wire. The free end was tied around the handle of a screwdriver so that it wouldn't spring back against the heating coil of the stove and get hot.
The candy thermometer near the top of the picture is highly recommended and costs about four bucks.
Finally, notice the small air bubble that has just reached the surface. I potted a total of five pickups in two sessions a couple of weeks apart and never saw what you would call a rush of bubbles. Instead, bubbles would kind of percolate to the surface one or two at a time for several minutes.
J. Atchley July, 2000