Re-wetting BP to screen

[Redrocketman]

I'll make it quick, just screened a 0.5kg batch but didn't wet it enough, didn't bind and breaks up much too easily.

Are you able to carefully reduce to gun meal ( mill ) re wet and screen black powder without affecting dextrin binding qualities?

[NeighborJ]

Dextrin can be reactivated SGRS cannot. It'll be fine, if it was dried fast then you may not need to re-mill it. If it is still damp then it may still be crumbly. Is the dex at least 4%? Any less only binds well if it has been pressed and corned.

[Redrocketman]

Nope. According to my old gospel (old!!) weights are :

Kno3 : 74.6 Gm

Ch : 13.5 Gm

S: 11.9 Gm

DX: 1.5 Gm

Hmm that's 1.5%.....

[pyrojig]

I personally would use the 4%. Although lesser amounts will work your BP granules will suffer strength. The loss of speed versus strength of BP grain is minimal . I have taken and rewetted BP Meal from the ricing powder process/ or the fines from BP hulls

[Redrocketman]

All turned out spot on. Added 2.5% dextrin to bring to 4.0%, re-wetted properly, screened and dried thoroughly. The best, cleanest burning, powerful BP I've yet made!! Nice strong granules

[pyrojig]

Good job! 😎

Glad to see you got it dialed in

Edited December 4, 2016 by pyrojig

[Redrocketman]

Thanks mate!!

[CrossOut]

I was going to say you can easily remill it and add more Dex but you got it solved

[JmFnG]

I recently had the same issue. Polverone ribbons were a bit too crumbly, even when fully dried. 2.5% dex and 20% water. An experienced pyro bud suggested I was shy on water.

Any thoughts on that assessment? I was told 15-18% water, but ended up at 20% before it held together well.

Next time, I'll bump up the dex a bit and see how it goes...just curious if anyone out there has an opinion on the water factor.

[NeighborJ]

IMO the powder won't stick together well until I add at least 16% water but I wouldn't go over 18%. The dex needs to be 4% unless it's pressed or your making granulated rocket fuel. The few times I've exceeded 20% water I've found the kno3 started recrystalizing and the granuals stuck together as a large clump.

[OldMarine]

Since polverone is more of a filler than burst, I'd go with 5% dextrin and the same amount of water you've been using. I tried 3% dex and mine was still too crumbly so I went back to the standard 5%.

 

Edit: NeighborJ beat me to the punch!

Edited December 17, 2016 by OldMarine

[Nessalco]

Guess I'm odd. I use 3% red gum and denatured alcohol to granulate powder - though I usually prefer to puck and corn using no binder. If making screen mixed polverone, I use 4% dex like folk have suggested.

Edited December 17, 2016 by Nessalco

[Mumbles]

There's a lot of bullshit, superstitions, and myths floating around about BP. The most important thing is to do what works for you. 2.5% dex should be sufficient if the dex is good. I normally use 5% though just to ensure rock hard granules. It's cheap anyway. To be honest I never measure the amount of water I add. I typically start at 20% straight water with a splash of alcohol and go from there. I suspect the charcoal source really is the biggest factor as to how much water you need. Some varieties are "thirstier" than others. The consistency is the important part. I wet it to a clay-like consistency, and I let the BP or polverone temper for about 15-20 min to ensure the dex is fully activated and the water is fully distributed. All said I probably add 22-25% water if I had to guess. If you use hot water for making polverone, you can use a little less, like 22-23%. Stirring and re-screening goes a long way to helping it not stick together and drying faster.