Powder moisture resistance

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Stophel

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Got a question. I have not reloaded in many years. Life gets in the way. All my stuff has been stored in a shed. Nothing has gotten soaking wet (surprisingly), but water does get in the building, and the humidity in this area is absolutely horrendous. I had primers in a big plastic tote, safe and dry, and from what I've read, it's basically impossible for humidity in the air to destroy them, but what about gunpowder? I have some Unique and 2400 in the old cardboard cans. I also have some other powders sealed in the plastic jugs or steel cans, and I'm not so much worried about them. The cardboard cans have not been compromised, and the powder inside seems fine, and I'm fairly confident it's all ok, but I just want to ask if you all think long term humidity might affect it through the cardboard can.

I guess there's one way to find out, and I'll go ahead and make up a little ammo from it soon just to see how it does.
 
I would be more concerned about age and highest storage temperatures the powders endured as powder deterioration/stability is dependent on those two factors.

From Alliant - https://www.alliantpowder.com/resources/catalog/2018_Alliant_Powder.pdf

"HOW TO CHECK SMOKELESS POWDER FOR DETERIORATION

Although modern smokeless powders contain stabilizers and are basically free from deterioration under proper storage conditions, safe practices require a recognition of the signs of deterioration and its possible effects.

Deteriorating smokeless powders produce an acidic odor and may produce a reddish brown fume. (Don’t confuse this with common solvent odors such as alcohol, ether and acetone.) Powder deterioration can be checked by opening the cap on the container and smelling the contents. Powder undergoing deterioration has an irritating acidic odor.

Dispose of deteriorating smokeless powders immediately. Check to make certain that powder is not exposed to extreme heat as this may cause deterioration. Such exposure produces an acidity which accelerates further reaction and has been known, because of the heat generated by the reaction, to cause spontaneous combustion."​

https://www.hodgdonreloading.com/reloading-education/safety/gunpowder-stability

"Smokeless Propellant

The main ingredient of smokeless propellant, comprising from about 55% to 90% of the composition, is nitrocellulose. The process of creating nitrocellulose leaves remnant acid in the material. This acid immediately starts decomposing the finished product. Left alone the decomposition will reach the stage where the propellant becomes unstable and self-ignites. This process resulted in massive explosions at U.S. Government arsenals after World War I.

To increase the life of the smokeless propellant, a stabilizing chemical is used. This “stabilizer” reacts with the acid to slow down the decomposition process. However, as the stabilizer reacts with the acid it is consumed. After the stabilizer is totally consumed, the propellant is no longer protected from the internal acid.

The entire stabilizer / decomposition process is a time and temperature function – the higher the temperature, the shorter the safe life of the powder. Even moderate temperature, over extended time, leads to propellant decomposition. As a rule of thumb, any temperature over that which is comfortable to a person is accelerating the decomposition of smokeless propellants.

Under proper storage, modern smokeless powder can last for decades. However, this does not mean the reloader can ignore how the powder is stored, particularly if in an uncontrolled environment such as a garage or storage building."​
 
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Thanks to the fairly recent component shortage problem I've made it a point to use up my oldest powders and they would be the ones i had stored out in the shed for a year (can get hotter than hell and humid) . I did something right, accidently. Better to be lucky than smart ? In a effort to get me to move my reloading equipment from the house to the shed my wife kept suggesting I put in AC out there , never got around to it.
 
"any temperature over that which is comfortable to a person is accelerating the decomposition of smokeless propellants."

I think anything over 68 degrees is uncomfortable.... so I'm pretty much always uncomfortable (91 degrees right now). It has been in this outbuilding for about eight years, and it does get H O T here.

It's all dark gray and flaky, though. Just the normal light aroma. No red stuff, no weird stink.

Thank you all. ;)
 
A generalized example of chemical reaction rate increase with temperature is the Arrhenius Equation.

https://en.m.wikipedia.org/wiki/Arrhenius_equation

It's generally not linear, but exponential as shown by the plot shapes. There's also activation energy "humps" between the initial and final states that have to be reached for a reaction to initiate. A common example would be striking a match - providing the activation energy for the combustion of the match head, and as it continues, matchstick.
 
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