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| SENSITIVITY OF BLACK POWDER TO STATIC DISCHARGE By Wayne McLerran |
Posted 4/14/18
It’s been many years since I designed and published an article on a semi-
automatic black powder (BP) loading system consisting of an electronic
powder dispenser, digital scale, fiber optics cable, a tall stand and a
drop tube. By pressing a single button the dispenser trickled out a
precise charge of BP down the drop tube into the case setting on the
digital scale platen. The dispenser stopped when the scale registered
the programmed powder weight to within +/- 0.1 grains. Knowing this,
a fellow shooter recently asked if I was concerned about using the setup
with black powder since the dispenser is constructed out of plastic and
has a plastic reservoir which potentially could build up a static charge.
Prior to building the loading system and due to a similar concern, I
researched the subject extensively, experimented with subjecting BP to
high voltage static discharges, and was convinced that any static charge
created by the dispenser would not be sufficient to ignite BP. 20 years
later I continue to use the same setup without any problems. But the
subject continues to come up in many of the online BPCR forums and is
therefore worthy of additional discussion.
My experiments with attempting to ignite BP consisted of the following.
Using Goex 2Fg and 3Fg I first pounded it to dust with a hammer with no
reaction. Several piles of the dust were then subjected to high voltage
discharges of approximately 100,000 volts with a hand tester used to
test static discharge damage thresholds in integrated circuits. The
discharge caused some of the small granules to move but none of the
samples ignited. Around the same time a fellow by the name of Barry
Bush published two excellent and lengthy articles on BP safety in the
1999 spring and summer editions of The Black Powder Cartridge News.
Mr. Bush is obviously a very knowledgeable guy and did a good amount of
experimenting to determine the sensitivity of BP to heat, pressure and
static discharge ignition. He found BP much more sensitive to heat than
smokeless. He also found that BP is not very sensitive to shock, and is
much less sensitive to high voltage sparks than smokeless powder. Barry
passed sparks of up to 20,000 volts directly through BP with absolutely
no ignition. Goex Fg, 2Fg, and 4FA (unglazed powder) BP was used. The
4FA powder was used to see if the lack of graphite would allow the
powder to ignite. He said that it is conceivable that a 100,000-volt
spark from a fingertip could ignite BP, but the chances are very remote,
which I proved to myself by my experiments detailed above.
In summary Barry said, “Many common perception of black powder come
from those who lack practical experience, and they often reflect
confusion with other explosive materials. Modern smokeless powder has
an excellent safety record, but in some respects smokeless can be more
dangerous than black: it is more likely to give extreme pressures from an
overload, more susceptible to decomposition, and under some
conditions, more sensitive to electrical discharges.” In closing he
further stated, “Black powder has managed to outlive most of its
detractors, and hopefully will continue to do so. Meanwhile, shooters
can ill afford to repeat folklore, speculation and hearsay which may
come back to haunt them.” The last sentence refers to past and
possible future government regulation on BP due to incorrect and
misleading information.
To further reinforce the above comments that BP is not sensitive to
static discharge, go to the following links at the Connecticut
Muzzleloaders website: http://www.ctmuzzleloaders.
com/ctml_experiments/sparks/sparks.html and http://www.
ctmuzzleloaders.com/ctml_experiments/electric_ignition/eignition.
html. The spark experiment is similar to the ones both Barry Bush and I
ran. The key to understanding the differences in the two
ctmuzleloaders.com experiments is the high voltage sparks in the first
experiment and those in Barry Bush’s and my experiments do not contain
sufficient energy (power) to heat the BP particles to the ignition point.
Electrical power (measured in watts) is the combination of voltage and
current. Static discharges generated from friction on plastic containers
or sliding ones foot on carpet and touching another object are typically
at very high voltages but the current levels are very low. The second
ctmuzleloaders.com experiment was based on using a capacitor, an
electrical energy storage device to ignite the powder. Although the
voltage level was significantly lower the capacitor provided a much
higher current source when discharged through the powder, which was
sufficient to heat the powder to the ignition point.
Another question that comes up now and then is based on concerns
about static buildup on plastic containers used for shipping and storing
BP, especially when pouring the powder out of the container. What
many BP shooters do not realize is the containers are made of antistatic
plastic. Although antistatic plastic can be made in several colors, clear,
red, etc., the plastic containers BP is shipped in are typically black and
contain small amounts of carbon to make the plastic slightly conductive
to electricity (antistatic). So pouring BP out of the containers cannot
build up a static charge.
The development of antistatic plastic was the result of the
semiconductor industries need to reduce the cost of shipping integrated
circuits (ICs) in the 1980’s, which were commonly shipped in
"conductive" aluminum tubes at the time. Some ICs are sensitive to even
low levels of static discharge. Most of my career was spent in the
semiconductor industry and I remember reading at the time that
materials with a surface resistance of as much as several hundred
thousand ohms per square inch would drain away any static charge.
Using a standard VOM (volt ohm meter) or multi-meter, one can actually
determine if the plastic used in BP shipping bottles is antistatic.
While writing this article I grabbed a black plastic bottle of Swiss 1.5Fg
and my handy Harbor Freight multi-meter, the one they give away if you
purchase anything at the store. With the meter set on ohms and the
sharp-tip probes inserted into the plastic about an inch apart, the
resistance was around 300,000 ohms, sufficient to eliminate a static
charge buildup. Just to double check, I also used an expensive multi-
meter with the same results. By the way, typical non-treated plastic is
an excellent insulator (has extremely high to infinite resistance) and
therefore will not drain off a static charge unless ambient humidity
levels are high; it’s wet or sprayed with a conductive material, which
brings me to some solutions if you are still concerned about static
charges building up and igniting BP.
Plastic powder-dispenser reservoirs can be lined with aluminum foil,
sprayed with Static Guard or other brands of antistatic sprays to lower
the surface resistance and drain off static charges. Spraying with a
water-diluted detergent solution and allowing the surface to dry will
temporarily eliminate static buildup as will wiping with a fabric softener
sheet used when drying clothes. Or go to the following link (http:
//www.instructables.com/id/Creating-Anti-Static-Spray/) to easily
make a solution from three common household ingredients.
I'm certainly not suggesting one can be careless when using BP, but the
experiments discussed here and the additional information presented
should cause you to reconsider the warnings and unsubstantiated myths
we in the shooting community have been passing around about BP safety.
Wishing you great shooting,
Wayne
It’s been many years since I designed and published an article on a semi-
automatic black powder (BP) loading system consisting of an electronic
powder dispenser, digital scale, fiber optics cable, a tall stand and a
drop tube. By pressing a single button the dispenser trickled out a
precise charge of BP down the drop tube into the case setting on the
digital scale platen. The dispenser stopped when the scale registered
the programmed powder weight to within +/- 0.1 grains. Knowing this,
a fellow shooter recently asked if I was concerned about using the setup
with black powder since the dispenser is constructed out of plastic and
has a plastic reservoir which potentially could build up a static charge.
Prior to building the loading system and due to a similar concern, I
researched the subject extensively, experimented with subjecting BP to
high voltage static discharges, and was convinced that any static charge
created by the dispenser would not be sufficient to ignite BP. 20 years
later I continue to use the same setup without any problems. But the
subject continues to come up in many of the online BPCR forums and is
therefore worthy of additional discussion.
My experiments with attempting to ignite BP consisted of the following.
Using Goex 2Fg and 3Fg I first pounded it to dust with a hammer with no
reaction. Several piles of the dust were then subjected to high voltage
discharges of approximately 100,000 volts with a hand tester used to
test static discharge damage thresholds in integrated circuits. The
discharge caused some of the small granules to move but none of the
samples ignited. Around the same time a fellow by the name of Barry
Bush published two excellent and lengthy articles on BP safety in the
1999 spring and summer editions of The Black Powder Cartridge News.
Mr. Bush is obviously a very knowledgeable guy and did a good amount of
experimenting to determine the sensitivity of BP to heat, pressure and
static discharge ignition. He found BP much more sensitive to heat than
smokeless. He also found that BP is not very sensitive to shock, and is
much less sensitive to high voltage sparks than smokeless powder. Barry
passed sparks of up to 20,000 volts directly through BP with absolutely
no ignition. Goex Fg, 2Fg, and 4FA (unglazed powder) BP was used. The
4FA powder was used to see if the lack of graphite would allow the
powder to ignite. He said that it is conceivable that a 100,000-volt
spark from a fingertip could ignite BP, but the chances are very remote,
which I proved to myself by my experiments detailed above.
In summary Barry said, “Many common perception of black powder come
from those who lack practical experience, and they often reflect
confusion with other explosive materials. Modern smokeless powder has
an excellent safety record, but in some respects smokeless can be more
dangerous than black: it is more likely to give extreme pressures from an
overload, more susceptible to decomposition, and under some
conditions, more sensitive to electrical discharges.” In closing he
further stated, “Black powder has managed to outlive most of its
detractors, and hopefully will continue to do so. Meanwhile, shooters
can ill afford to repeat folklore, speculation and hearsay which may
come back to haunt them.” The last sentence refers to past and
possible future government regulation on BP due to incorrect and
misleading information.
To further reinforce the above comments that BP is not sensitive to
static discharge, go to the following links at the Connecticut
Muzzleloaders website: http://www.ctmuzzleloaders.
com/ctml_experiments/sparks/sparks.html and http://www.
ctmuzzleloaders.com/ctml_experiments/electric_ignition/eignition.
html. The spark experiment is similar to the ones both Barry Bush and I
ran. The key to understanding the differences in the two
ctmuzleloaders.com experiments is the high voltage sparks in the first
experiment and those in Barry Bush’s and my experiments do not contain
sufficient energy (power) to heat the BP particles to the ignition point.
Electrical power (measured in watts) is the combination of voltage and
current. Static discharges generated from friction on plastic containers
or sliding ones foot on carpet and touching another object are typically
at very high voltages but the current levels are very low. The second
ctmuzleloaders.com experiment was based on using a capacitor, an
electrical energy storage device to ignite the powder. Although the
voltage level was significantly lower the capacitor provided a much
higher current source when discharged through the powder, which was
sufficient to heat the powder to the ignition point.
Another question that comes up now and then is based on concerns
about static buildup on plastic containers used for shipping and storing
BP, especially when pouring the powder out of the container. What
many BP shooters do not realize is the containers are made of antistatic
plastic. Although antistatic plastic can be made in several colors, clear,
red, etc., the plastic containers BP is shipped in are typically black and
contain small amounts of carbon to make the plastic slightly conductive
to electricity (antistatic). So pouring BP out of the containers cannot
build up a static charge.
The development of antistatic plastic was the result of the
semiconductor industries need to reduce the cost of shipping integrated
circuits (ICs) in the 1980’s, which were commonly shipped in
"conductive" aluminum tubes at the time. Some ICs are sensitive to even
low levels of static discharge. Most of my career was spent in the
semiconductor industry and I remember reading at the time that
materials with a surface resistance of as much as several hundred
thousand ohms per square inch would drain away any static charge.
Using a standard VOM (volt ohm meter) or multi-meter, one can actually
determine if the plastic used in BP shipping bottles is antistatic.
While writing this article I grabbed a black plastic bottle of Swiss 1.5Fg
and my handy Harbor Freight multi-meter, the one they give away if you
purchase anything at the store. With the meter set on ohms and the
sharp-tip probes inserted into the plastic about an inch apart, the
resistance was around 300,000 ohms, sufficient to eliminate a static
charge buildup. Just to double check, I also used an expensive multi-
meter with the same results. By the way, typical non-treated plastic is
an excellent insulator (has extremely high to infinite resistance) and
therefore will not drain off a static charge unless ambient humidity
levels are high; it’s wet or sprayed with a conductive material, which
brings me to some solutions if you are still concerned about static
charges building up and igniting BP.
Plastic powder-dispenser reservoirs can be lined with aluminum foil,
sprayed with Static Guard or other brands of antistatic sprays to lower
the surface resistance and drain off static charges. Spraying with a
water-diluted detergent solution and allowing the surface to dry will
temporarily eliminate static buildup as will wiping with a fabric softener
sheet used when drying clothes. Or go to the following link (http:
//www.instructables.com/id/Creating-Anti-Static-Spray/) to easily
make a solution from three common household ingredients.
I'm certainly not suggesting one can be careless when using BP, but the
experiments discussed here and the additional information presented
should cause you to reconsider the warnings and unsubstantiated myths
we in the shooting community have been passing around about BP safety.
Wishing you great shooting,
Wayne