Powder moisture one more time

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Brent
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Powder moisture one more time

Post by Brent » Sat Aug 31, 2019 8:33 pm

I've been trying to learn more about powder lately, so for educational purposes, I decided to measure the moisture content of three different lots of Swiss 1.5 fg powder. The short answer is that they are very consistently 1% water or a little less. Across three different lots there was a variation of only 0.27%. The long answer is below. I encourage others to try this with different makes of powder like Goex OE, for instance.


I put 300.0 grs of three powders well spread out in foil pans that were about 5” square.

I put these in my food dehydrator for 24 hrs while set on 135 F. I did not verify the temp, but it’s probably fairly close. A fan runs air through the machine continuously.

Tonight, I removed them directly from the dehydrator to the scale and weighed each one. In general, they lost 1% of their weights in moisture or other volatiles.

Lot # 210.113 lost 3.0 grs of mass
Lot # 18/01/2016 lost 2.2 grs
Lot # 120:208 lost 2.6 grs

While I have been typing this, all three regained about 1 gr of mass. This is expected as they cool down. When powders cool they absorb a little moisture. Even sand would do this. I don’t know if they will regain all they lost but I’ll let them sit until tomorrow night and see what happens. I seriously doubt they will recover all that they lost, but perhaps.

Anyway, these powders have about 1% moisture in them at most. I can check with my records from historic powders, but I think this is within the norm or slightly on the dry side. And all in all, looking across the range of moistures, we are talking about a spread of 0.8 grs or 0.8/300 *100= 0.27%, or about a quarter of 1 percent. I cannot believe that is pragmatically significant.

And now you know.

PS. Years ago, Pete Mink, Bob Mullen and Ed Stutz ran experiments to see how much moisture powder could pick up if left in open air conditions ranges from 50% to 100% relative humidities. Their results suggest that moisture uptake from the environment is exceedingly small. On the range of 0.5% or less. I have graphs of this for those interested.

PPS. I also have a table of velocities as a function of moisture. These were from an old (circa late 19th century) book that was not mine and I no longer have a record of the title. But two things are noteworthy. First, the author was working with powder moistures in the same range as I found here, and further that the variation in moistures in this powders would be responsible for about 20 fps in loads that were running in the mid 1500s (presumably a smallish caliber like a .32-40, I would guess). I have a table of these values, but no other data remains from that book (it was not mine).
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Kurt
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Re: Powder moisture one more time

Post by Kurt » Sun Sep 01, 2019 7:50 am

Brent, What are you using to measure the moisture?

Brent
PostsCOLON 1648
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Re: Powder moisture one more time

Post by Brent » Sun Sep 01, 2019 7:58 am

Just the difference between the before and after drying weights
I'm not from here, I just live here.

Kurt
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Re: Powder moisture one more time

Post by Kurt » Sun Sep 01, 2019 8:52 am

I might give it a try. I have some Swiss in two different lots as well some OE 2 and 1.5 F.
I just started a new lot of 2F OE and worked up several 5 shot ladder loads for the .45-90 and 84 and 85 grain loads will throw one shot out out of the group that is 2" or less out 1-1/2"- 2" and it's starting to make me wonder if I was collecting moisture leaving the powder drop open over night if I didn't get finished loading the day before. Humidity is running 59% in the basement.
The bullet weight is 534 gr and I use the heavy end of the cast lot that weigh the same.
Lodi is getting close and I need to get this worked out. That one shot hitting at 4 MOA at 200 will make a dirt digger at the 1K.
I'm not having much luck with the new case of 1.5 swiss. I can't get it better then a 6-7" group at 200 using three different bullets designs.

Brent
PostsCOLON 1648
JoinedCOLON Sun Nov 20, 2005 9:12 pm
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Re: Powder moisture one more time

Post by Brent » Sun Sep 01, 2019 6:28 pm

Kurt, what is the lot number or date on the new lot of powder?

those friends of mine that I mentioned above left powder out overnight on their porches where humidities hit 100% and the most their powders picked up was like 0.5". Half of one percent. Don't worry about moisture absorption in your basement!

I'll have at least three different powders to shoot at Lodi. It will not really be a match for me. It will be load testing - again. Back to the bad ol' days.
I'm not from here, I just live here.

Brent
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JoinedCOLON Sun Nov 20, 2005 9:12 pm
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Re: Powder moisture one more time

Post by Brent » Sun Sep 01, 2019 7:54 pm

In the for what it is worth, after 24 hrs all three powders regained nearly exactly their original weight. The two came up just 0.2 grns short of their original 300 grs and the third came up 0.6 grs short of 300 grs after 24 hrs of ambient basement conditions.

Brent
I'm not from here, I just live here.

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