Prepping your cast bullets - Page 2

**Unclenick** · June 9, 2020, 10:58 AM

Big Al,

I read the article you linked to with interest. Thank you for that. It wasn't until the fellow mentioned high humidity making sticking more difficult that it convinced me there really is a static mechanism involved, even if I can't see what it is. I am also perplexed that PP (recycle #5) would be necessary. PE (recycle #2) has nearly identical electrical properties and PE is also famous for picking up static charges, as is styrene (recycle #6). All three have been used as the dielectric material in commercial capacitors for decades. Indeed, I once replaced a missing belt on a Van de Graaff generator in my college's physics lab by making a new one out of heavy (like 6 mil) PE sheet. It worked a treat. I demonstrated the repaired apparatus to a class at its start one day, immediately after the students had filed in. We observed its ability to achieve an impressive charge and discharge deteriorated rapidly as all the breathing students in the room humidified the air.

I have been using a denatured alcohol slurry to PC bullets. I will have to see if I can do some experiments with tub rolling, though I'll need a low RH day, it seems. If the dust is actually removing an induced charge from the inner surface of the tub and dragging it to bullets, some other details, like the role of the airsoft pills need to be understood. I can think of a couple of tests that might show it, and if an induced charge is the mechanism, it can be forced using a high voltage supply and a capacitance around the turning tub. Time to play.

big al hunter · June 9, 2020, 10:24 PM

Unclenick, I studied the internet and YouTube pretty hard before I decided to start casting my own. I didn't like the idea of greasy lube, and all of the mess that I could make with it. Most sources said a plastic tub or bottle. A couple said to use recycle numbers to determine which is best. So I checked out what the numbers refer to for materials, and what material would be likely to cause a static charge friendly environment. Like you said, there are several that will work. I found a chart that showed levels of static for each type of plastic. The material in recycle #5 was the highest on the list. So, I tried that first. Mostly because I have a ready supply of tubs. Never had an issue with it, so never tried any others.

I thought about making the slurry too. But that involves another product to buy, store and keep out of reach of my kids.

reddog81 · June 10, 2020, 12:40 PM

Quote:

Originally Posted by Unclenick

I will have to see if I can do some experiments with tub rolling, though I'll need a low RH day, it seems. If the dust is actually removing an induced charge from the inner surface of the tub and dragging it to bullets, some other details, like the role of the airsoft pills need to be understood. I can think of a couple of tests that might show it, and if an induced charge is the mechanism, it can be forced using a high voltage supply and a capacitance around the turning tub. Time to play.

The impact humidity has is highly dependent on the powder being used. I've had a hard time getting Harbor Freight powders stick even with low RH. The higher quality PC's seem to have minimal impact. I have no problems even at 75% RH with most of the powders I use. I use a section of 3" PVC pipe for the plastic tub. I have no idea what # it would correspond to, but it works as well if not better than the #5 tubs I started with and it holds 15 lbs of bullets without falling apart.

**Unclenick** · June 10, 2020, 03:54 PM

PVC is recycle #3, and, per Al's approach I looked it up on a triboelectric table and it is actually slightly higher in (-) charge propensity than PP on that chart, and PP is followed by PE, followed by PU, followed by Saran (polyvanilidine chloride, or PVDC). So you may have picked a winner. If you want to maximize charge from rubbing, you would pair that with something that is high on the (+) charge side of the table. Glass beads might be a good candidate. I may well try that experiment.

Needless to mention, you don't want humidity and you certainly don't want conductors like graphite around. You want the plastic to be free of dirt or grease that might affect the insulating properties and charge accumulation.

June 9, 2020, 10:58 AM	#26
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	Big Al, I read the article you linked to with interest. Thank you for that. It wasn't until the fellow mentioned high humidity making sticking more difficult that it convinced me there really is a static mechanism involved, even if I can't see what it is. I am also perplexed that PP (recycle #5) would be necessary. PE (recycle #2) has nearly identical electrical properties and PE is also famous for picking up static charges, as is styrene (recycle #6). All three have been used as the dielectric material in commercial capacitors for decades. Indeed, I once replaced a missing belt on a Van de Graaff generator in my college's physics lab by making a new one out of heavy (like 6 mil) PE sheet. It worked a treat. I demonstrated the repaired apparatus to a class at its start one day, immediately after the students had filed in. We observed its ability to achieve an impressive charge and discharge deteriorated rapidly as all the breathing students in the room humidified the air. I have been using a denatured alcohol slurry to PC bullets. I will have to see if I can do some experiments with tub rolling, though I'll need a low RH day, it seems. If the dust is actually removing an induced charge from the inner surface of the tub and dragging it to bullets, some other details, like the role of the airsoft pills need to be understood. I can think of a couple of tests that might show it, and if an induced charge is the mechanism, it can be forced using a high voltage supply and a capacitance around the turning tub. Time to play. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

June 9, 2020, 10:24 PM	#27
big al hunter Senior Member Join Date: March 12, 2011 Location: Washington state Posts: 1,558	Unclenick, I studied the internet and YouTube pretty hard before I decided to start casting my own. I didn't like the idea of greasy lube, and all of the mess that I could make with it. Most sources said a plastic tub or bottle. A couple said to use recycle numbers to determine which is best. So I checked out what the numbers refer to for materials, and what material would be likely to cause a static charge friendly environment. Like you said, there are several that will work. I found a chart that showed levels of static for each type of plastic. The material in recycle #5 was the highest on the list. So, I tried that first. Mostly because I have a ready supply of tubs. Never had an issue with it, so never tried any others. I thought about making the slurry too. But that involves another product to buy, store and keep out of reach of my kids. __________________ You can't fix stupid....however ignorance can be cured through education!

June 10, 2020, 03:54 PM	#29
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	PVC is recycle #3, and, per Al's approach I looked it up on a triboelectric table and it is actually slightly higher in (-) charge propensity than PP on that chart, and PP is followed by PE, followed by PU, followed by Saran (polyvanilidine chloride, or PVDC). So you may have picked a winner. If you want to maximize charge from rubbing, you would pair that with something that is high on the (+) charge side of the table. Glass beads might be a good candidate. I may well try that experiment. Needless to mention, you don't want humidity and you certainly don't want conductors like graphite around. You want the plastic to be free of dirt or grease that might affect the insulating properties and charge accumulation. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle