4 replies to this topic

[Bowerz]

Hi, i make my own BP and can't work out why it burns so hot! i filled up a highlighter cap with it and put a fuse in then taped round, and when i went back the cap had melted but the paper came and selotape round the outside hadn't. I'm using THIS KNO3, THISSulfur and Charcoal made from matchsticks heated with no oxgen and soaked in Citreonela (spelling?) liquid fire torch fuel (when this is lit, the oxgyen is pulled out of the container thus away from the sticks and also heats it to an extent. I use a 75:15:10 ratio, hand ground with a P&M to a consistancy of thick flour (about twice the granual size, but not as big as caster sugar). I know eBay isn't the best place to get chems but im gonna be re crystalising my KNO3 soon too see if the purity of that is the problem and also i am in the process of making a ball mill.

P.s. The burn time of the cap full was less than half a second but it still made the cap melt a rediculess amount!

Edited by Bowerz, 22 April 2009 - 06:48 PM.

[Arthur Brown]

If you had read COPAE then you would already have read the passage I quote below

"These results indicate by calculation
that the explosion of the powder produces a temperature
of about 3880°." --That's really hot!

BP is meant to be hot if it wasn't it would be concrete!

Good fast BP leaves little trace of it's flame temperature because it burns rather quickly!

[Bowerz]

Ahh, i see, i knew it was hot but i wouldn't have though it was to the extent of melting plastics withing half a second! Also, my BP (well KNO3 as this happens with my smoke generatin devices) leaves behind a thick, but airy (if you see what i mean) powder. I know my powder is fairly slow so that could be part the problem.

[pyromaniac303]

Often powders which are slow or don't burn cleanly leave behind molten particles that melt plastics. After milling my willow meal for 2 hours, I can light a couple of grams on a piece of paper with only small scorch marks.

What colour is the powder left behind?

*White spherical droplets usually indicated potassium nitrate is not being consumed, caused by either incorrect weights (over oxidised), not ground fine enough, or impure potassium nitrate.
*Burnt/blackened remenants mean the powder isn't burning cleanly, has too much fuel, or hasnt been ground fine enough.
*Any other colour usually indicates an impurity. A while back there was a post on red residue left, and it was found to be a problem with the potassium nitrate.

Judging by the granule size you mentioned, I'd say you need to try grinding better.

You could try taking a sample of about 1g of your existing powder, and grinding it really well for 20 minutes or longer in your mortar and pestle. Test this and compare the residue to the one before. If it burns much more cleanly then I think you've solved the problem.

Edited by pyromaniac303, 22 April 2009 - 09:37 PM.

[Arthur Brown]

Ultra fine BP is made from airfloat charcoal and dust ingredients and milled for hours in a good mill! This will combust completely and leave nothing behind. Poorly integrated powder of coarse grains will form a lot of slag which will spatter all over the burn site leaving damage marks.