Charcoal lumps

[Weasel]

I thought I had my stars all figured out, until my latest 7 batches of stars all turned out to be crap. I made D1, white, green, and other compositions that all burn fine in powder form. Once made into stars, however, they leave big nasty coals that are a major fire hazard. The star burns, but the shape of the star is kept in a glowing red mass of charcoal. it is easily broken up with a screwdriver, but air tests have shown that air friction is not enough to break them up, they fall to the ground red hot. I was going to make more stars today, but i want to solve this problem before i end up with more useless stars. I have speculated as to why this is happening.

 

My number one hypothesis is that the stars are not dry, but one composition i make, tigertail, never leaves charcoal lumps behind. It receives the same drying time as all my other stars, the biggest difference i found was that it had 6% dextrin as opposed to 4 or 5%. but dextrin amount shouldn't make a difference, should it? My second hypothesis was that the compositions have not been miled long enough. But if this was the case, they would leave lumps in powder form too, which they don't. One of the comps that leaves lumps i mill for many hours, the kno3 white stars are milled plenty long but still leave lumps. chemical purity is good, except for the homemade dextrin, which could have some corn starch in it. everything seems in order, but all my stars - except tigertail - leave lumps. I'm back to the dryness theory, and i'm going to put my stars in a dehydrator and see what it does. I just don't understand why the tigertail comes out fine. do higher charcoal amounts lose water faster?

 

Anyway, I would like to see what other pyros have experienced and how this could be solved. Any suggestions? Thanks for reading.

[dagabu]

Weasel,

 

I have some willow stars drying since last September that still have not reached their dry weight. Sounds like wet stars to me. Yes, cut back on the dex, often 3% is enough for binding.

 

D

[Weasel]

Cool, should be an easy fix then, i have a gigantic food dehydrator that i don't use for food . I already put some stars in there to test it out, I think it should work well. The curious thing is that my tiger tail stars have 6% dextrin, much higher than normal, and they dry out without the need of a dehydrator. Time to make blue stars, can't wait for the color!

 

 

[jwitt]

I wondered a similar thing, throwing a TT star and blowing on a slag lump really hard while it sits on the lid of my old BBQ. Neither of these things completely consume the ember lump. I am under the impression that this is normal behavior though. I believe (through reading) that streamers such as TT will "always" leave a glowing lump when burned on the ground- that lump sheds the fire dust that gives TT its effect in the sky as the star is propelled through the air. As such, it's interesting that your TT burns completely away. My 1/4" (before prime) Chrys #6 burned completely away after 4 days of drying, room temp, with 20% relative humidity.

 

When you say "air tests" are you shooting from a star gun, mine, or shell, or are you simply chuckin' stars into the air?

 

Also, I've heard this casual star dryness test can be done if you don't have the data to test by weight:

 

Put a handfull of stars in a sealed ziplock baggie, sit it in the sun for a bit, and see if any condensation develops after a bit of time.

 

Curious to see what folks say about this! (I'm just a rookie, Weasel, hoping to tag along and increase our knowledge)

 

PS also an interesting note from D about dextrin. Might try dropping my level one of these days and see how hard the stars turn out.

Edited April 23, 2010 by jwitt

[dagabu]

I switched to NC and a touch of alcohol for the binder with no Dex. They dry in a few days.

 

D

[Weasel]

It appears results can be very different for every pyro... I have used nc lacquer before to bind stars, the result, lumps.....

 

I use a star gun to test my stars, haven't gotten any shells up this year yet, still stockpiling stars and materials...

[dagabu]

Man!! I wonder what is going on with your stars? Bad KNO3?

 

D

[50AE]

This is a PITA. I had a similar problem, but I easily inderstood that the dextrin was the fucker ruining everything. It was a technical grade dextrin, which had some very hard brown lumps that were leaving much dross when my stars burned. I screened the crap through a 200mesh screen and I filtered a lot of crap. Now everything is ok.

Check your chemicals for crap lumps.

[Weasel]

My chemicals are all fine and pure, except my dextrin, which is homemade. my dextrin is still fine and unburnt, but im wondering if it isn't comepletely 100% dextrin and if this affects lump formation. I have quite a few stars in a dehydrator now, and there is slight improvement. The stars haven't been in there more than a few hours, but they were air dried to begin with, which makes me worry when they still leave lumps after drying even more.

 

I am positive my KNO3 is pure, i got it from ihaveadotcom.com and he claims it is 99% pure, says it right on the tub. I'm still wondering why my tigertail burns fine. The main differences between it and other bp based comps i have (like slow gold, which leaves lumps) is that it has a higher charcoal content and a higher dextrin content than comps like slow gold. I don't see why a higher dextrin or a higher charcoal content would prevent charcoal lumps. The comp was milled, but so was slow gold(without the metals, of course.). it was pumped with the same amount of water as slow gold. it was dried the same way. I used the same chemicals, same dextrin, same techniques and processes of manufacture. I just don't get it... i don't live in a humid environment... I even cut some tigertail with a lot of water to see if it's water amount that could be messing it up. The tigertail still burns fine. My blackpowder also burns fine when granualated or made into metal streamer stars. The only thing i can do for now is let them sit in that dehydrator for a few days.

 

On a more positive note, i made pinkho blue! lovely color, burns clean and deep even in powder form. I have a few of the blue stars drying, i hope they don't end up making lumps after they dry. I also found it interesting that it burnt fairly quickly, even though i didn't bother to make the chemicals fine at all, theres big lumps of kclo4 in it. I only made 10 grams, and i wanted to see how it would burn if it was lumpy. turns out it can be lumpy and perform beautifully.

 

I think i will upload a video of some of my stars, that could possibly help. Thanks for all the advice thus far.

[MilkyJoe]

hey, what type of wood for charcoal are you using?

 

First I would try a different binder if you have one, then if no change, give a different wood a try.

[Weasel]

The dehydrator has helped a lot after 12 or 14 hours, some of the stars that left lumps no longer leave lumps. Granite stars and slow gold still have problems. I suspect wetness may still be an issue on the slow gold, but I think the high % of zinc is what makes the lumps in the granite stars. I think milling the zinc green rather than screening it may help (without the zinc, of course)

 

The lesson from all this : your stars need to be as dry as they were in powder form to work properly.

 

I think all the charcoal stars should turn out fine, the granites problems are what i need to solve now.

 

I use pine, by the way.

Edited April 24, 2010 by Weasel

[Ventsi]

If you get a lump of glowing yellow/green mass after you lit a Granite star on the ground that is ABSOLUTELY fine. They NEED to be propelled at high speeds to shed that off. And about the slow gold, do they just burn and leave a lump of red-glowing mass? Thats fine too, again they need to be going through the air to shed that off and give off the fire dust.

 

And you absolutely don't need to mill zinc stars. Screening is plenty for them. I've made them at least half a dozen times.