How does humidity affect powder? A new experiment

MK20

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I spoke to a tech at hodgdon the other day on this subject. He said that the seals on their powder bottles allow exchange of air and humidity but are designed to keep things like rain out should the package of powder sit on your porch after delivery in a rainstorm.
 

Doom

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First and foremost all of discussion about powder and humidity is fundamentally wrong. Unless I have missed something in my 12 years of reloading, neither Hodgdon (IMR,HXXXX), Alliant, or VV ship their powder hermetically sealed. It isn't necessary. Every container is shipped with a security seal so thet tampering will be evident. As for the container it is most likely HDPE and is essentially non porous. When properly sealed (tightly capped) there is little if any exchange of air between the container and ambient air. If the container breathed, you would not see it bulge out in hot weather and bulge in in cooler weather

AS for the powder itself, it does not have humidity. It does have a moisture content and if left openly exposed to a different environment it will come to equilibrium with that environment. This is a function of mass transfer and occurs, due to the hygroscopic nature of nitrocellulouse, on the surfaces of the powder kernel. Much of the moisture is contained within the kernel and must travel to the surface to be absorbed by the air. Time is required for this transfer to take place. The same is true in reverse, When handling powder most is contained in a packed column, either in the container, in the measure or in the case. Very little air is is directly in contact with the powder and that air tends to stay with the kernel. Also, referencing humidity is an error since the amount of moisture in air is not measured by relative humidity but rather by absolute humidity or humidity ratio. For instance, air at 75F and 60% RH has the same moisture content ratio as air at 60F and 100% RH.

All of the test that I have seen on powder and humidity purposely dry or add moisture to the powder which will always result in a change in mass and burn rate (H2O is a combustion diluent).

An 8 Lb container has a volume of about .3 cubic feet. That is a grand total of .021 lbs of dry air and .0004 lbs of water if the air is 75F and 100% Relative Humidity. A pound of powder would have about 5% moisture, or .05 lbs of water, and if it absorbed all of the moisture from the air, which it wouldn't, it would contain .0504lbs (0.8%) of water. This is a bounding calculation showing the limit of what could happen.

As for powder being shipped with a specific humidity, usually around 60%, this is actually true. It has little to do with moisture content of the powder. It is to prevent the buildup of static electricity in the handling process. This is to prevent explosions.

Unless you live in a Arctic or Desert environment, or leave you powder container open for long periods of time, or put it in the wife's dryer the moisture content of your powder isn't likely to move much.
 

Doom

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I spoke to a tech at hodgdon the other day on this subject. He said that the seals on their powder bottles allow exchange of air and humidity but are designed to keep things like rain out should the package of powder sit on your porch after delivery in a rainstorm.
Really, rain?
 

Yondering

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First and foremost all of discussion about powder and humidity is fundamentally wrong. Unless I have missed something in my 12 years of reloading, neither Hodgdon (IMR,HXXXX), Alliant, or VV ship their powder hermetically sealed. It isn't necessary. Every container is shipped with a security seal so thet tampering will be evident. As for the container it is most likely HDPE and is essentially non porous. When properly sealed (tightly capped) there is little if any exchange of air between the container and ambient air. If the container breathed, you would not see it bulge out in hot weather and bulge in in cooler weather

AS for the powder itself, it does not have humidity. It does have a moisture content and if left openly exposed to a different environment it will come to equilibrium with that environment. This is a function of mass transfer and occurs, due to the hygroscopic nature of nitrocellulouse, on the surfaces of the powder kernel. Much of the moisture is contained within the kernel and must travel to the surface to be absorbed by the air. Time is required for this transfer to take place. The same is true in reverse, When handling powder most is contained in a packed column, either in the container, in the measure or in the case. Very little air is is directly in contact with the powder and that air tends to stay with the kernel. Also, referencing humidity is an error since the amount of moisture in air is not measured by relative humidity but rather by absolute humidity or humidity ratio. For instance, air at 75F and 60% RH has the same moisture content ratio as air at 60F and 100% RH.

All of the test that I have seen on powder and humidity purposely dry or add moisture to the powder which will always result in a change in mass and burn rate (H2O is a combustion diluent).

An 8 Lb container has a volume of about .3 cubic feet. That is a grand total of .021 lbs of dry air and .0004 lbs of water if the air is 75F and 100% Relative Humidity. A pound of powder would have about 5% moisture, or .05 lbs of water, and if it absorbed all of the moisture from the air, which it wouldn't, it would contain .0504lbs (0.8%) of water. This is a bounding calculation showing the limit of what could happen.

As for powder being shipped with a specific humidity, usually around 60%, this is actually true. It has little to do with moisture content of the powder. It is to prevent the buildup of static electricity in the handling process. This is to prevent explosions.

Unless you live in a Arctic or Desert environment, or leave you powder container open for long periods of time, or put it in the wife's dryer the moisture content of your powder isn't likely to move much.

"everyone else is wrong" - then proceeds to contradict themselves in multiple places while reiterating many of the same things that were already said by someone else. LOL

And yeah, you've definitely missed something in your incredible 12 whole years of reloading experience. Most powder bottles do breathe with the cap on, and are not tightly sealed. Squeeze them and listen to the air come out, and then suck back in again.
 

MarkyMark007

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maybe bottles are not the main source of moisture in the powder.

when we make ammo, we expose powder to air in much bigger surface than it is in canister. when we weight it in the pan. I presume that main humidity transfer to the powder is done that way... maybe...
 

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This is classic of our population. Reloaders by and large have zero education or real knowledge of chemistry, engineering, or physics. It is the low grade, shade tree, sub-layer of a pretty scientific based industry and we just do a lot of trial and error to develop a load. Load development by nature is just uneducated people formalizing the process of trial and error. I always laugh when people on this site act like they're developing "empirical data". Hell, most people here spell it like "impirical" 🤣

You can try to reverse engineer scientific knowledge, talking about relative vs absolute humidity and explain something the rest of us have just plain observed and understood. Or join the rest of us and simply leave some powder out for a week and then load it and shoot it and see what it does. Talk about it in psuedo science. Or just try it out and see the evidence.
 
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Doom

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This is classic of our population. Reloaders by and large have zero education or real knowledge of chemistry, engineering, or physics. It is the low grade, shade tree, sub-layer of a pretty scientific based industry and we just do a lot of trial and error to develop a load. Load development by nature is just uneducated people formalizing the process of trial and error. I always laugh when people on this site act like they're developing "empirical data". Hell, most people here spell it like "impirical" 🤣

You can try to reverse engineer scientific knowledge, talking about relative vs absolute humidity and explain something the rest of us have just plain observed and understood. Or join the rest of us and simply leave some powder out for a week and then load it and shoot it and see what it does. Talk about it in psuedo science. Or just try it out and see the evidence.
This is classic of our population. Reloaders by and large have zero education or real knowledge of chemistry, engineering, or physics. It is the low grade, shade tree, sub-layer of a pretty scientific based industry and we just do a lot of trial and error to develop a load. Load development by nature is just uneducated people formalizing the process of trial and error. I always laugh when people on this site act like they're developing "empirical data". Hell, most people here spell it like "impirical" 🤣

You can try to reverse engineer scientific knowledge, talking about relative vs absolute humidity and explain something the rest of us have just plain observed and understood. Or join the rest of us and simply leave some powder out for a week and then load it and shoot it and see what it does. Talk about it in psuedo science. Or just try it out and see the evidence.
You may not agree with what I have said and you are certainly entitled to your opinion but that doesn't make it correct. I will leave it at that.
 

NamibHunter

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Thought this was interesting: higher humidity makes the powder swell and then a powder measure will be off:




Another good reason for weighing all your charges, and controlling humidity in your reloading room.
 

NamibHunter

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One of the best write-ups on the topic so far:

 

NamibHunter

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In my own experiments, some 8 lbs powder bottles leaked and humidity slowly changed (Kestrel Drop left inside recording humidity over a week), but some did not and humidity stabilized in a few hours and then remained constant. I guess it all depends on the damage done to the seal. Maybe the leak rate is just very slow and it will take months to see a change.

The choice of polymer (same as medicine bottles) appears to be air tight.

My worry is if you open a bottle of powder sealed in the factory at 65% relative humidity at 89 deg F and you load a 100 rounds over 2 hours, in winter with RH at 35% and 50 deg F, then the first round will not have the same burn rate as the last one.

Should you pour the powder into a dispenser/powder measure and let it sit for half a day to equilibrate, before you use it?
 

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Somebody in a different thread suggested these wi-fi enabled humidity sensors, cheap enough, and small enough to go into a one pound container, so i tried them last week:



Works remarkable well, and the app is real easy to set up. The 3 humidity Sensors connect to a small wifi base station that remains plugged into a power socket. Your phone then connects to the base station via Bluetooth and download the latest data, once you are in range.

I did not enable the cloud storage. Made in China, but quality looks good, and cheaper than Kestrel ($69 for 3 sensors). Can add more sensors later on.

So these sensors are now inside the three powder containers that i use most frequently, with a two-way Boveda humidity pack in each to keep RH close to 49%, which is about where my reloading room is. The Boveda humidity packs won’t last forever, so this is a way to detect when they are depleted and need to be replaced.

Hopefully this solves the problem where powder humidity changes lead to large changes in muzzle velocity… which can take you out of the node.
 
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Doom

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In my own experiments, some 8 lbs powder bottles leaked and humidity slowly changed (Kestrel Drop left inside recording humidity over a week), but some did not and humidity stabilized in a few hours and then remained constant. I guess it all depends on the damage done to the seal. Maybe the leak rate is just very slow and it will take months to see a change.

The choice of polymer (same as medicine bottles) appears to be air tight.

My worry is if you open a bottle of powder sealed in the factory at 65% relative humidity at 89 deg F and you load a 100 rounds over 2 hours, in winter with RH at 35% and 50 deg F, then the first round will not have the same burn rate as the last one.

Should you pour the powder into a dispenser/powder measure and let it sit for half a day to equilibrate, before you use it?
You worry to much. First your humidity in the jug will change as ambient temperature changes without anything other than dry bulb temperature changing. If you really want to see what is going on look at dew point, not relative humidity. Dewpoint will remain constant for constant moisture content with changing ambient temperature.
 

NamibHunter

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Humidity pack:



If you live in a desert, then the 32% pack might be more useful to you. If you live on the Gulf Coast and load in an outside shed (no AC), then the 62% packs might be best.
 

NamibHunter

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You worry to much. First your humidity in the jug will change as ambient temperature changes without anything other than dry bulb temperature changing. If you really want to see what is going on look at dew point, not relative humidity. Dewpoint will remain constant for constant moisture content with changing ambient temperature.

I get what you are staying: RH is a relative measurement, and depends on temperature, and dew point is what matters more. Fair point.

This device monitors temperature as well, and then calculates and trends Dew Point and Vapor Pressure Deficit (VPD). Would be happy to see a fairly constant dew point, when temperature drifts down on cold winter days. Might put a canister outside to see what happens.

Idea is to run an experiment to see if SD comes down post “humidity stabilization project”. We shall see.
 
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🥴 Let me throw another monkey wrench into the gears. ;)

The issue of leakage. After loads are finished, they can leak moisture unless the cases are sealed with some kind of sealant. If you ever seen how a bag of potato chips expands or contracts with the change in altitude, then you can probably get an idea of what's at work with how a cartridge might leak, in terms of moisture content. So, if you're someone like me loading just a couple hundred feet above sea level then goes hunting at several thousand feet, that difference in pressure can cause cartridges to leak and actually change the moisture content of the powder charge in a loaded cartridge, depending on the difference in humidity/dew-point and the length of exposure at the difference in altitude. o_O

Hmmm??? Is there anything else we can worry about? :LOL:
 
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NamibHunter

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🥴 Let me throw another monkey wrench into the gears. ;)

The issue of leakage. After loads are finished, they can leak moisture unless the cases are sealed with some kind of sealant. If you ever seen how a bag of potato chips expands or contracts with the change in altitude, then you can probably get an idea of what's at work with how a cartridge might leak, in terms of moisture content. So, if you're someone like me loading just a couple hundred feet above sea level then goes hunting at several thousand feet, that difference in pressure can cause cartridges to leak and actually change the moisture content of the powder charge in a loaded cartridge, depending on the difference in humidity/dew-point and the length of exposure at the difference in altitude. o_O

Hmmm??? Is there anything else we can worry about? :LOL:

You clearly have a lot of reloading experience, and your comments are all valid. My goal is instead of giving up (and living with all these problems), i am more interested in how to resolve them. So very open to fresh ideas.

Yes, loaded rounds exchange air with ambient once there is a pressure differential, either because a low pressure/high pressure system moved in, or you took your ammo on a plane to a match. Have seen this happen over a 3 month period by weighing loaded rounds on a milligram scale, posted some results elsewhere on this site. Effect is very real. Tried sealing the cases (using the Ranger industrial sealant), that stopped the weight changes on 90% of the loaded rounds, but the variable amount of “glue” in the neck changed the neck tension and did more harm than good to the SD of the batch. So a failed experiment. If you know of a better solution, i would be curious.

Not trying to “worry”, not trying to scare anyone, just trying to identify what problem is keeping my SDs at 7-9, and what to do to get it to 4-5 fps….

Btw: Bullet weld was the major issue for me, caused my SDs to start off at 12-14 fps, and mostly got that resolved: Tumble in walnut media with 2 teaspoons of mineral spirits plus a tiny amount of polymer car wax mixed in, for 2 hours only controlled via a timer (don’t over clean the inside of the necks), use Neolube nr 2 on the inside of the neck, seat long, reseat the morning of a shoot. That took my SD from 12 to 8. So on to the next problem.

Looking for ideas to get to 4, and what experiments to run, not trying to tell anybody what to do…. Humidity control looked like a viable candidate.
 
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straightshooter1

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You clearly have a log of reloading experience, and your comments are all valid, but my attitude is instead of giving up and living with all these issues, i am more interested in how to resolve them. So very open to fresh ideas.

Yes, loaded rounds exchange air with ambient once there is a pressure differential, either because a low pressure/high pressure system moved in, or you took your ammo on a plane to a match. Have seen this happen over a 3 month period by weighing loaded rounds on a milligram scale, posted some results elsewhere on this site. Effect is very real. Tried sealing the cases (using the Ranger industrial sealant), that stopped the weight changes on 90% of the loaded rounds, but the variable amount of “glue” in the neck changed the neck tension and did more harm than good to the SD of the batch. So a failed experiment. If you know of a better solution, i would be curious.
If I were flying, I'd have my cartridges in a sealed container that can withstand the pressure difference. And, in the container I'd have the appropriate humidity control pack. Then I wouldn't take the cartridges out of the container until I was ready to use them. Leakage isn't instantaneous and neither is the transfer of moisture. So, the time from removing the cartridges from a climate controlled container to chambering and firing, shouldn't amount to much of a factor.

For hunting, some kind of sealant would be best; something like some manufactures use on some of their ammo. Wish I knew what that is.

Not trying to “worry”, not trying to scare anyone, just trying to identify what keeps my SDs at 7-9, and what to do to get it to 4-5 fps….

Btw: Bullet weld was the major issue for me, caused my SDs to start off at 12-14 fps, and mostly got that resolved: Tumble in walnut media with 2 teaspoons of mineral spirits plus a tiny amount of polymer car wax mixed in, for 2 hours only controlled via a timer (don’t over clean the inside of the necks), use Neolube nr 2 on the inside of the neck, seat long, reseat the morning of a shoot. That took my SD from 12 to 8. So on to the next problem.

Looking for ideas to get to 4, and what experiments to run, not trying to tell anybody what to do…. Humidity variance looked like a viable candidate.

Agree, about not cleaning the inside of the necks. After annealing and cleaning the outside of the necks with steel wool, I like to tumble with white rice (medium grain) after I've sized them having used Imperial Sizing Die Wax. The rice absorbs the wax lube and apparently leaves a very thin coating on the inside of the neck, which makes for nice and consistent seating and no bullet weld; at least, no detectable weld in a 6 month period that I've experienced. The outside of the cases are cleaned nicely, though not what one can get with wet tumbling, but that's not my goal anyway. Here's what my cases look like after 5 firings using this method:

6.5 PRC Lapua Brass.JPG
 

Yondering

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You clearly have a lot of reloading experience, and your comments are all valid. My goal is instead of giving up (and living with all these problems), i am more interested in how to resolve them. So very open to fresh ideas.

Yes, loaded rounds exchange air with ambient once there is a pressure differential, either because a low pressure/high pressure system moved in, or you took your ammo on a plane to a match. Have seen this happen over a 3 month period by weighing loaded rounds on a milligram scale, posted some results elsewhere on this site. Effect is very real. Tried sealing the cases (using the Ranger industrial sealant), that stopped the weight changes on 90% of the loaded rounds, but the variable amount of “glue” in the neck changed the neck tension and did more harm than good to the SD of the batch. So a failed experiment. If you know of a better solution, i would be curious.

Not trying to “worry”, not trying to scare anyone, just trying to identify what problem is keeping my SDs at 7-9, and what to do to get it to 4-5 fps….

Btw: Bullet weld was the major issue for me, caused my SDs to start off at 12-14 fps, and mostly got that resolved: Tumble in walnut media with 2 teaspoons of mineral spirits plus a tiny amount of polymer car wax mixed in, for 2 hours only controlled via a timer (don’t over clean the inside of the necks), use Neolube nr 2 on the inside of the neck, seat long, reseat the morning of a shoot. That took my SD from 12 to 8. So on to the next problem.

Looking for ideas to get to 4, and what experiments to run, not trying to tell anybody what to do…. Humidity control looked like a viable candidate.

On bullet weld - I’ve been experimenting with a method of coating the case necks in wax (on the inside) to prevent this. Letting some ammo sit now to see if it welds or not.

The other thing I do currently is to rinse my sized cases in laquer thinner, saving and reusing the solvent so that it contains enough case lube to leave a thin and consistent film in the case necks. This has shown me benefits in consistent seating force and reduced likelihood of cold welding.
 

NamibHunter

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Thanks for the ideas, it is much appreciated.

Guess a small Pelican pistol case would work to prevent a pressure change affecting the water content of the loaded rounds (and therefore burn rate and MV) when flying.

Pelican cases, like many others, have a pressure relief valve, so at least you can equalize pressure before opening it, once you arrive in say Denver Colorado, or Tajikistan - for a once in a lifetime Marco Polo sheep hunt, that will cost you at least $50K. 😊

Will will try the rice tumbling media. I know Greg Dykstra of Primal Rights is a strong proponent as well.

I seal my hunting ammo with Ranger Industrial Sealant (multiple colors are available), which is advertised as suitable for sealing primer and bullet. Hornady used to sell a primer sealant, but it was discontinued. Both worked fine to keep water out, but they have their own downsides too (increased and variable seating force, if you try to seat the bullets deeper before firing). That was not a good sign.

Found it easy to seal the primers, but rather tricky to properly seal the bullets. Some cases still leaked and changed weight by almost 0.1 grain over 3 months, and perhaps 10% of the cases ended up not properly sealed. [Best theory i could come up with: Old cases often have deep scratches on the inside, and i guess the sealant is seeping deep into the neck, and some cases have more or deeper scratches than others…. But who really knows!]

 
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Yondering

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looks like another problem in the making, and industry is already selling products for non-existent problem...

There's a big difference between a problem you didn't know about, and a problem that doesn't exist. I'm not sure which one you're referring to here, but both humidity and cold welding are known and documented concerns that do affect internal ballistics. You either not knowing about them, or not shooting at a level that shows their influence, does not mean they are a non-existent problem.

Plenty of uneducated people drive their cars around without having the oil changed, but that doesn't mean engine oil life is a non-existent problem. It just means those people are ignorant.
 
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