Merlin back for more education

[Merlin]

Six weeks ago I made good BP. Got good lift and breaks on 3 inch shells. Launched three test shells to observe star performance today and disaster. Using same powder and charge shells barely went a hundred feet before barely breaking on return journey to earth. One actually hit the ground before going poof. The only difference I know is the powder is I waited until we had rain to avoid any fire hazard. The humidity has been very high but the powder was kept in a shop with AC to dry the air and maintain constant temperature. Using same plastic shells. Just cant figure it. Any guesses? I am kinda down about it - thought I had the basic BP licked.

Edited September 2, 2014 by Merlin

[Mortartube]

I can only assume, that even though you took all of those precautions, that dampness has somehow got into the powder, given that the same stuff worked so well before,

 

Is it possible that you made your shells in a good regulated environment, and when they experienced a large change in temperature/humidity range when you took them out to fire them, that condensation formed inside the sealed plastic cases?

[db5086]

My guess is moisture also.I have the same problem with lift at times as well. Some days I get 300' and some days the shell barely comes out of the mortar. I'm going to see what a graphite glaze does to the powder in regards too consistency. I've never had an issue with commercial 2fg so that may be the ticket.

[rogeryermaw]

In central arkansas, the air is pretty soupy. I don't call my b.p. stellar or anything but it has been consistent. What process are you using to granulate? Are you test fitting your shells in the mortar you fire them out of? For a 3 inch, I wrap until the gap is no greater than 1/8" on one side. Are you using a carrier or straight b.p.? Binders? I'm no expert. Just lucky probably, but the only times I have had weak lift had to do with loose fitting shells. If you feel that moisture is an issue, try keeping your powder sealed with a package of silica gel to absorb moisture.

[Merlin]

I honestly dont know. I am using straight BP granulated 2FA. It worked well before but not yesterday with either paper or plastic shells. I am going to launch more dummy shells today to see what happens. I know something is wrong because if moisture absorption of BP can degrade it to the point I experienced yesterday no pryotechnican would dare put on a display for fear of moisture degraded BP! Back to the drawing board. By the way my bp was made with red gum and alcohol to wet for granulation.

[FlaMtnBkr]

Was it the actual same BP as before or just made the same way with the same chemicals?

 

A little water (4-5% IIRC) actually improves BP power. And unless you have contaminates, BP should not be hygroscopic.

 

Edit: typo and more info

Edited September 3, 2014 by FlaMtnBkr

[Merlin]

The exact same BP. Can only assume it absorbed moisture. From now own will store in zip locks with drierite and coat with graphite. Starting over with new meal.

BP is hydroscopic.

Edited September 4, 2014 by Merlin

[dagabu]

The exact same BP. Can only assume it absorbed moisture. From now own will store in zip locks with drierite and coat with graphite. Starting over with new meal.

BP is hydroscopic hygroscopic.

 

Sorry to play the grammar police but a hydroscope is an optical device for viewing objects below the surface of water.

 

To see if you have excess water in your BP, put it into a zip lock and set it in the sun for an hour, if droplets of water form on the top of the bag (inside) then it's still wet. BP can absorb moisture BUT think back to Horatio Nelson and his many years on the high seas firing on other ships, the BP was only in casks, not sealed, waxed or oiled. Once thoroughly dried, BP can be stored in paper or wooden containers with little worry.