8 replies to this topic

[GreenGenie]

I have been making cone fireworks that work very well. In fact a little too well. They burn a little too high and too fast for the area I have available in which to set them off. I would like to slow down the burn rate to reduce the height and diameter of the spray and to increase the duration of the firework.

The compositions in question have been black powder with 20% metal. Iron, Titanium and Aluminium. I tried adding extra metal - iron 40% thinking that this might slow it down. It did not. I got twice as many sparks but the firework was still as large and as fast. I am interested in additives for this specific purpose; but I am also interested in this as a more wide ranging question for all firework compositions.

Previously when I have made cones, I have compacted the mixture. This did not produce very good results. The alumimium would start well but would quickly overheat burning up the cone. The iron composition would be disappointing. I had one burn all the way through leaving a solid cone of ash where the material had not ejected. Leaving the mix uncompacted produced a very fine display.

It may be that the solution is in the way I am compacting the mix but I would still like to know if there are things that I can add to slow down the reaction speed.

I have read on the forum about using plain flour and sodium bicarbonate but the posts did not give enough information for me to understand how to, when, how much and when not to use these.

I make the cones using 4 paper drinking cones glued together with wallpaper paste. I tape a strip of Potassium Nitrate soaked paper fuse (Touch paper) to the inside of the cone with the fuse hanging out of the top. I cut two circular discs of cardboard for the base and tape them together. I put these onto the adhesive side of a rectangle of aluminium foil roofing tape so that they are stuck firmly in place. Then I fit the cone over the top of these so that they fit snuggly inside forming the base of the cone with the bottom of the cone also sticking to the tape. I then fold the aluminium adhesive up, overlapping and wrapping the base of the cone. I cover the base with a second rectangle of adhesive tape. the cone is ready. I make a funnel out of another single paper cup with the bottom snipped off and pour in the composition.

Previously, when I was using compacted composition I would sit the glued together cone water cups upside down in a tin that contains concrete, set to make a fit with the inverted cones. I would then pour in the composition and compact it carefully before fitting the base.

Pictures
http://www.wildewate.../pyro/cone1.jpg
http://www.wildewate.../pyro/cone2.jpg

[knackers]

you could try increasing the charcoal content, or reducing the oxidiser in your Bp, being over fueled or under oxidized will decrease the burn rate

[GreenGenie]

Thankyou Phill

As soon as I read it I thought "Of course!!". I have tested your idea by reducing the oxidiser and it worked very well. Thankyou.

[seymour]

While I would second Phills suggestion of charcoal (it gives more prettiness while slowing it!) Carbonates (Barium carbonate or Sodium bicarbonate, usually) also do the same thing, with out the added charcoal sparks.

Charcoal it will be.

Edited by seymour, 20 April 2009 - 05:20 AM.

[knackers]

Thankyou Phill

As soon as I read it I thought "Of course!!". I have tested your idea by reducing the oxidiser and it worked very well. Thankyou.

i'm glad it worked, sometimes its hard to see the trees for the forest, i had the same problem with streamer stars burning to quickly and also asked on here how to fix, " thanks seymour", there is also another way to slow it down, i was using hard wood from my fruit trees and the Bp was pretty good i thought, until i found some willow, and that put my Bp into overdrive, are you using willow ? or another fast timber? an easy to come by hard wood will slow it down somewhat, perhaps easier to find and/or cost nix to get

[seymour]

I believe Citrus trees are really bad for fast black powder (therefore really good for slowing it down). I personally like the idea of just using fast charcoal and more of it. More of it is needed to slow it down, and so you get more pretty sparks!

[knackers]

I believe Citrus trees are really bad for fast black powder (therefore really good for slowing it down). I personally like the idea of just using fast charcoal and more of it. More of it is needed to slow it down, and so you get more pretty sparks!

yes, i'de go that way too, the longer burning embers of the charcoal look absolutely magnificent, ( another effect all by itself )

[GreenGenie]

Yes Phill, you are right again. Willow it is. I have bought some lumpwood charcoal recently. In fact I opened the packet for the first time yesterday but didnt use it. I was rather disappointed to find that it was very coarse. Will try it thought. Perhaps its courseness will be an advantage and produce bigger sparks.

[GreenGenie]

Thankyou guys. Some good insights.