Pure paraffin wax potting, and de-potting the pickup
Dec 9, 2019 10:47:28 GMT -5
straylight likes this
Post by antigua on Dec 9, 2019 10:47:28 GMT -5
This is a new thread expanding on the experiment in this thread guitarnuts2.proboards.com/thread/8739/wax-potting-experiment-capacitance-microphonics , but this time instead of using beeswax, I've used paraffin wax, which has a lower melting point and seems to be less viscous liquid and a softer solid, than beeswax. I checked the values after potting, and then used heated denatured alcohol to extract the paraffin from the coil, and checked its values again.
As in the other thread, the test pickup is a Strat type pickups that I had wound to 8,000 turns with 42AWG wire. The paraffin was heated to about 180 degree Fahrenheit.
Summary: paraffin performs similar to beeswax when reducing microphonics and inducing capacitance. Submerging the paraffin potted pickup in heated denatured alcohol for about a half hour removed about half of the wax and caused the pickup to become microphonic again.
Regarding capacitance, the unpotted pickup started with a capacitance of 142pF. After potting, it got as high as 220pF, but for whatever reason it ended up closer to 200pF all said and done. As would be expected, while the pickup is still cold, the wax mostly condenses around the outside of the pickup, and during that time the capacitance is unchanged, but once the pickup reaches the temperature at which the wax melts, the wax permeates the coil, releasing air bubbles. At this point, the capacitance increases, taking about one to two minutes to reach the peak capacitance, although for this test I repeatedly took the pickup out of the wax in order to measure it, causing it to cool. If left in the wax, I suspect the wax would permeate the entire coil in under a minute. For the last 10 minutes of a total of 30 minutes wax submersion, I increased the temperature of the wax from 180 to 205 degrees, but the capacitance didn't continue to increase during that time, so it seems that 180 degrees was sufficient to fully permeate the coil. The increase of capacitance was about the same with the paraffin and beeswax; about 50pF added.
Regarding the microphonics, The way I test this is by striking the pickup with a wooden spoon about a hundred times in order to capture peak voltage outputs on a voltage-by-frequency plot with the PCSU200. I forgot to get a baseline measurement for this pickup, but I have some from other pickups that are constructed the same way. Wax potting the pickup with paraffin appeared to mean it ever bit as anti-microphonic as compared to beeswax. After removing half of the wax with heated alcohol , the coil appeared to be as microphonic as an unpotted pickup. I think it stands to reason that the outer windings, where the wax can be most easily drawn away later, are the most responsible for microphonics, because they're under less compression than the inner windings.
Regarding weight, I bought a high precision scale, and weighed the pickup while wax potting. The initial weight of the pickup was 52.6 grams. Once fully potted, it settled at a weight of 54.2 grams, meaning the pickup carried, inside and outside, 1.6 grams of paraffin. I baked the pickups in the oven for an hour at 210 degree F, at which point the capacitance was unchanged, meaning the coil still retained all the wax, but all the wax outside of the coil melted away, and the weight was 53.4 grams, meaning that 0.8 grams had been outside of the coil, and 0.8 grams remained inside the coil. I boiled the pickup in alcohol for about 30 minutes, and this process removed some of the wax in the coil, and the final weight after this was 52.85 grams.
Regarding inductance, as the previous test showed, and as would be expected, the wax didn't change the inductance at all. But, apparently being filled with alcohol caused the inductance to drop to 1.7 henries, according to the DE-5000 LCR meter at 100Hz in series mode. Allowing the alcohol to evaporate for 30 minutes, the reported inductance increased to 1.9 henries, and after a day of drying, the inductance returned to 2.4 henries, giving me cause to believe the alcohol fully evaporated. I'm not sure why the alcohol caused the inductance to drop, it can't be due to heat alone, as baking the pickup in the oven to higher temps had virtually no effect on the inductance.
Attempting to remove the paraffin from the coil.. the first thing I did was bake the pickup in the oven at 210 F for about an hour, and aside from all traces of wax disappearing from the outside of the pickup, the electrical measurements suggested that all of the wax remained in the coil. Then, I heated alcohol with a double boiler to about 180 degrees, it was boiling, and submerged the pickup in there for about 30 minutes. As mentioned, the inductance decreased to 1.7 henries, and the capacitance jumped to 592pF while the coil contained alcohol. As the alcohol evaporated, the inductance returned to what it was, and the capacitance dropped to 174.25, only about half way towards the original 142pF of the unpotted coil, from 200pF. So it seems that the 30 minute heated alcohol submersion managed to remove about half the wax.
As mentioned above, the initial weight of the pickup was 52.6 grams. After being fully wax potted and then having the exterior wax melted away, it weighed 53.4 grams, and after the alcohol submersion and evaporation weighed 52.9 grams, also suggesting that about half the wax was removed. As the microphonic testing shows, the outer portion of coil appears to have more space within the windings than the inner portion of the coil, so it's probably more difficult for heated alcohol to draw the wax from those inner windings.
While capacitance was cut by half, the microphonics seems to be substantially restored, most likely because the it's the outer-most winding that are responsible for microphonics, and it's the outer most windings from which wax was able to escape in the heated alcohol.
In conclusion, it seems that much of the paraffin can be removed with heated alcohol. It might be the case that there are better solvents for the job, and it might be possible that hot soapy water works as well, but I tried alcohol because it's suggested for cleaning up wax removal, and is often used for herbal extraction, but I'm not a chemist, so this was a shot in the dark. Next I will try this on some production guitar pickups to see if "de-potting" is something that can be done to a pickup that has already been manufactured.
Paraffin Wax Dipping & Removal
No wax:
L: 2.449H
C: 142.14pF
R: 6.076 k ohms
W: 52.573 grams
1 second:
L: 2.444H
C: 142.24pF
R: 6.368 k ohms
W: 54.373g
10 seconds:
L: 2.451H
C: 141.22pF
R: 6.571 k ohms
W: 56.558 grams
30 seconds:
L: 2.450H
C: 141.29pF
R: 6.537 k ohms
W: 57.621 grams
1 minute:
L: 2.440H
C: 142.22pF
R: 6.650 k ohms
W: 57.177 grams
Note: bubbles seen coming from the flatwork holes
1.5 minute:
L: 2.443H
C: 143.21pF
R: 6.742 k ohms
W: 55.793 grams
2 minute:
L: 2.444H
C: 152.71pF
R: 6.756 k ohms
W: 54.704 grams
Note: bubbles from the flatwork and coil, wax appears to penetrate the coil now
2.5 minute:
L: 2.444H
C: 181.36pF
R: 6.828
W: 54.075 grams
Note: steady bubbles
3 minute:
L: 2.446H
C: 206.0pF
R: 6.880 k ohms
W: 54.728 grams
Note: steady bubbles, no visible wax
3.5 minute:
L: 2.450H
C: 220.0pF
R: 6.304 k ohms
W: 54.847 grams
Note: few bubbles
4 minute:
L: 2.447H
C: 213.1pF
R: 6.592 k ohms
W: 55.092 grams
Note: few bubbles, more cooling time between dips
4.5 minute:
L: 2.433H
C: 213.8pF
R: 6.695 k ohms
W: 54.826 grams
5 minute:
L: 2.445H
C: 212.3pF
R: 6.730 k ohms
W: 54.830 grams
6 minute:
L: 2.442H
C: 212.0pF
R: 6.841 k ohms
W: 54.574 grams
10 minute:
L: 2.446H
C: 205.6pF
R: 6.990 k ohms
W: 54.371 grams
20 minute:
L: 2.440H
C: 202.0pF
R: 7.048 k ohms
W: 54.255 grams
30 minutes, final 10 mins from 180 to 205 degrees F
L: 2.439H
C: 199.16pF
R: 7.247 k ohms
W: 54.159 grams
1 hour in an oven at 210 degrees F
L: 2.451H
C: 202.5pF
R: 6.628 k ohms
W: 53.359 grams
Note: pickup looks very clean, nox visible wax on the outside of the pickup
Submerging potted pickup in alcohol at 150F for 30 mins, immediately after
L: 1.682H
C: 592.1pF
R: 6.328 k ohms
W: 54.031 grams
Submerging potted pickup in alcohol at 150F for 30 mins, 1 hour later
L: 1.914H
C: 474.5pF
R: 6.023 k ohms
W: 53.720 grams
Submerging potted pickup in alcohol at 150F for 30 mins, 1 day later
L: 2.462H
C: 174.25pF
R: 6.068 k ohms
W: 53.000 grams
100kHz bode plot before potting, after, and then after alcohol submersion:
Extreme little microphonics:
Slight microphonics:
Substantial microphonics:
As in the other thread, the test pickup is a Strat type pickups that I had wound to 8,000 turns with 42AWG wire. The paraffin was heated to about 180 degree Fahrenheit.
Summary: paraffin performs similar to beeswax when reducing microphonics and inducing capacitance. Submerging the paraffin potted pickup in heated denatured alcohol for about a half hour removed about half of the wax and caused the pickup to become microphonic again.
Regarding capacitance, the unpotted pickup started with a capacitance of 142pF. After potting, it got as high as 220pF, but for whatever reason it ended up closer to 200pF all said and done. As would be expected, while the pickup is still cold, the wax mostly condenses around the outside of the pickup, and during that time the capacitance is unchanged, but once the pickup reaches the temperature at which the wax melts, the wax permeates the coil, releasing air bubbles. At this point, the capacitance increases, taking about one to two minutes to reach the peak capacitance, although for this test I repeatedly took the pickup out of the wax in order to measure it, causing it to cool. If left in the wax, I suspect the wax would permeate the entire coil in under a minute. For the last 10 minutes of a total of 30 minutes wax submersion, I increased the temperature of the wax from 180 to 205 degrees, but the capacitance didn't continue to increase during that time, so it seems that 180 degrees was sufficient to fully permeate the coil. The increase of capacitance was about the same with the paraffin and beeswax; about 50pF added.
Regarding the microphonics, The way I test this is by striking the pickup with a wooden spoon about a hundred times in order to capture peak voltage outputs on a voltage-by-frequency plot with the PCSU200. I forgot to get a baseline measurement for this pickup, but I have some from other pickups that are constructed the same way. Wax potting the pickup with paraffin appeared to mean it ever bit as anti-microphonic as compared to beeswax. After removing half of the wax with heated alcohol , the coil appeared to be as microphonic as an unpotted pickup. I think it stands to reason that the outer windings, where the wax can be most easily drawn away later, are the most responsible for microphonics, because they're under less compression than the inner windings.
Regarding weight, I bought a high precision scale, and weighed the pickup while wax potting. The initial weight of the pickup was 52.6 grams. Once fully potted, it settled at a weight of 54.2 grams, meaning the pickup carried, inside and outside, 1.6 grams of paraffin. I baked the pickups in the oven for an hour at 210 degree F, at which point the capacitance was unchanged, meaning the coil still retained all the wax, but all the wax outside of the coil melted away, and the weight was 53.4 grams, meaning that 0.8 grams had been outside of the coil, and 0.8 grams remained inside the coil. I boiled the pickup in alcohol for about 30 minutes, and this process removed some of the wax in the coil, and the final weight after this was 52.85 grams.
Regarding inductance, as the previous test showed, and as would be expected, the wax didn't change the inductance at all. But, apparently being filled with alcohol caused the inductance to drop to 1.7 henries, according to the DE-5000 LCR meter at 100Hz in series mode. Allowing the alcohol to evaporate for 30 minutes, the reported inductance increased to 1.9 henries, and after a day of drying, the inductance returned to 2.4 henries, giving me cause to believe the alcohol fully evaporated. I'm not sure why the alcohol caused the inductance to drop, it can't be due to heat alone, as baking the pickup in the oven to higher temps had virtually no effect on the inductance.
Attempting to remove the paraffin from the coil.. the first thing I did was bake the pickup in the oven at 210 F for about an hour, and aside from all traces of wax disappearing from the outside of the pickup, the electrical measurements suggested that all of the wax remained in the coil. Then, I heated alcohol with a double boiler to about 180 degrees, it was boiling, and submerged the pickup in there for about 30 minutes. As mentioned, the inductance decreased to 1.7 henries, and the capacitance jumped to 592pF while the coil contained alcohol. As the alcohol evaporated, the inductance returned to what it was, and the capacitance dropped to 174.25, only about half way towards the original 142pF of the unpotted coil, from 200pF. So it seems that the 30 minute heated alcohol submersion managed to remove about half the wax.
As mentioned above, the initial weight of the pickup was 52.6 grams. After being fully wax potted and then having the exterior wax melted away, it weighed 53.4 grams, and after the alcohol submersion and evaporation weighed 52.9 grams, also suggesting that about half the wax was removed. As the microphonic testing shows, the outer portion of coil appears to have more space within the windings than the inner portion of the coil, so it's probably more difficult for heated alcohol to draw the wax from those inner windings.
While capacitance was cut by half, the microphonics seems to be substantially restored, most likely because the it's the outer-most winding that are responsible for microphonics, and it's the outer most windings from which wax was able to escape in the heated alcohol.
In conclusion, it seems that much of the paraffin can be removed with heated alcohol. It might be the case that there are better solvents for the job, and it might be possible that hot soapy water works as well, but I tried alcohol because it's suggested for cleaning up wax removal, and is often used for herbal extraction, but I'm not a chemist, so this was a shot in the dark. Next I will try this on some production guitar pickups to see if "de-potting" is something that can be done to a pickup that has already been manufactured.
Paraffin Wax Dipping & Removal
No wax:
L: 2.449H
C: 142.14pF
R: 6.076 k ohms
W: 52.573 grams
1 second:
L: 2.444H
C: 142.24pF
R: 6.368 k ohms
W: 54.373g
10 seconds:
L: 2.451H
C: 141.22pF
R: 6.571 k ohms
W: 56.558 grams
30 seconds:
L: 2.450H
C: 141.29pF
R: 6.537 k ohms
W: 57.621 grams
1 minute:
L: 2.440H
C: 142.22pF
R: 6.650 k ohms
W: 57.177 grams
Note: bubbles seen coming from the flatwork holes
1.5 minute:
L: 2.443H
C: 143.21pF
R: 6.742 k ohms
W: 55.793 grams
2 minute:
L: 2.444H
C: 152.71pF
R: 6.756 k ohms
W: 54.704 grams
Note: bubbles from the flatwork and coil, wax appears to penetrate the coil now
2.5 minute:
L: 2.444H
C: 181.36pF
R: 6.828
W: 54.075 grams
Note: steady bubbles
3 minute:
L: 2.446H
C: 206.0pF
R: 6.880 k ohms
W: 54.728 grams
Note: steady bubbles, no visible wax
3.5 minute:
L: 2.450H
C: 220.0pF
R: 6.304 k ohms
W: 54.847 grams
Note: few bubbles
4 minute:
L: 2.447H
C: 213.1pF
R: 6.592 k ohms
W: 55.092 grams
Note: few bubbles, more cooling time between dips
4.5 minute:
L: 2.433H
C: 213.8pF
R: 6.695 k ohms
W: 54.826 grams
5 minute:
L: 2.445H
C: 212.3pF
R: 6.730 k ohms
W: 54.830 grams
6 minute:
L: 2.442H
C: 212.0pF
R: 6.841 k ohms
W: 54.574 grams
10 minute:
L: 2.446H
C: 205.6pF
R: 6.990 k ohms
W: 54.371 grams
20 minute:
L: 2.440H
C: 202.0pF
R: 7.048 k ohms
W: 54.255 grams
30 minutes, final 10 mins from 180 to 205 degrees F
L: 2.439H
C: 199.16pF
R: 7.247 k ohms
W: 54.159 grams
1 hour in an oven at 210 degrees F
L: 2.451H
C: 202.5pF
R: 6.628 k ohms
W: 53.359 grams
Note: pickup looks very clean, nox visible wax on the outside of the pickup
Submerging potted pickup in alcohol at 150F for 30 mins, immediately after
L: 1.682H
C: 592.1pF
R: 6.328 k ohms
W: 54.031 grams
Submerging potted pickup in alcohol at 150F for 30 mins, 1 hour later
L: 1.914H
C: 474.5pF
R: 6.023 k ohms
W: 53.720 grams
Submerging potted pickup in alcohol at 150F for 30 mins, 1 day later
L: 2.462H
C: 174.25pF
R: 6.068 k ohms
W: 53.000 grams
100kHz bode plot before potting, after, and then after alcohol submersion:
Extreme little microphonics:
Slight microphonics:
Substantial microphonics: