33 replies to this topic

[Creepin_pyro]

If I make a Strontium Nitrate based star, do I need to use just Alcohol for wetting? I'm thinking about using Red gum as a binder, but I'm unsure about how well these stars will dry. Strontium Nitrate is hydroscopic (right ? ), so will wetting them with water mean they wont dry?

I know I sound stupid

[BigG]

They will dry just make sure that when the weather become cooler you store them in an air-tight box. In the UK, you might want to consider Carbonate. Strontium carbonate give a good red colour (true, but as strong as nitrate, but good none the less), and is not hygroscopic.

[Phoenix]

For my sodium nitrate stars, I used 5% shellac with ordinary methylated spirit as a binder. This had no problems drying, (either from the sodium nitrate dampening or from the shellac binder getting driven in) and the stars were rock hard. Out of curiosity, I also dampened some sodium nitrate with water and left it out, and it dried fully after a day or two.

[alany]

Are the shellac bound stars hard to light?

i've had troubles with that in the past, how do you prime them?

(Mind sharing the formula BTW?)

[Phoenix]

The yellow stars were basically BP made with sodium nitrate, plus 5% dextrin. The formula is in the star formulas thread.

These were round stars, and if the formula was used for cut or pumped stars they may not even need priming, but the round ones seemed a little hard to light and I had a few blow blind from a star gun, so I just rolled some ordinary meal BP on them, no step prime or anything. As I mentioned in my original post, I didn't add a binder to the BP, as it was only a thin layer and stuck to the surface OK.

I have had problems with shellac bound colour stars (red). I have only made two very small batches so far, but both have been difficult to light. They were made with only K chlorate, shellac and Sr carbonate, and would not light as they were. The first batch, I rolled in sulphurless BP, which was a mistake, as it usually just burned off, leaving the star unignited. I still have most of them.

The second, very small batch (10g) had a little charcoal added, which helped, but most still belw blind. I ended up incorporateing the second batch into a sulpurless BP and dextrin matrix, and making a 20mm comet from them. Like this, or in a sulphuless fountain, they easily ignite, and give a pretty good effect, so I can still put them to good use. (I pressed the fountain, not rammed it).

[alany]

What do you use for sulfurless BP, 8:3?

[Phoenix]

Oops, sorry. The formula I used was:

Potassium Nitrate.......70
Charcoal.....................30

Burnt as meal, straight out of the mill, this looks pretty uninspiring as a lift or propellant charge (though OK as a prime) but pressed and corned, it burns almost as fast as normal BP.

Bear in mind that this usually failed to ignite the stars (which were a modified version of Jerronimo's red, replacing sugar with the same amount of shellac). An intermediate prime would probably be necessary.

Another point, don't make the mistake I did of dampening a 20% shellac formula with alcohol. They got driven in and took weeks to dry.

Edited by Phoenix, 30 June 2004 - 07:07 PM.

[Jerronimo]

Mmmm usually this formula takes fire very easily.
I think the sulferless BP prime is causing problems, the ignition point is higher because there's no sulfer in it.

How did you test them in a shell or a stargun?

[Phoenix]

Sorry, not actually your formula, but one based on it, with the same proportions but replacing sugar with shellac. I thought I'd edited that, but apparantly not. I have now.

The sulpurless BP was noticably harder to ignite than normal BP, but ignited from both a star gun and a shell (well, rocket header actually), using granulated sulphurless BP as the lift/burst charge. (Dim orange streak not followed by red).

[paul]

A very good looking red formula which ignetes very easily is as follows:

KClO4 70
Red Gum 10
SrCO3 15
Charcoal 1
Dextrin 4

It?s a mixture from Bleser, and if you use 25-35% alcohol for binding, these stars only need an outer BP coating...

And SrCO3 is much cheaper than strontiumnitrate.

[sasman]

This afternoon i made a small batch of Ruby Red..I took the formula from passfire.. It contains Both Parlon RedGum and dextrin ..there is no mention of weither i use water(dextrin) Alcohol(Redgum) or Acetone(parlon)..?.. I reckon any of the solvents will work but not sure whats best..

I burnt a small test pile and was not impressed with the colour it produced.. i was hoping for a real deep bright red.. but all i got was a slowish burning orangeish reddish colour..leaving a large amount of residue.

Now i know you got to try them in a stargun to see the full effect but i had at least hoped it would burn as bright red as say Red road Flare..it was no way near ..

How do i fine tune this formula?..I tried adding some more magnalium but that make's it burn way to fast.. I have made some Red perchlorate/carbonate stars which used parlon and the flame was similar to that it had an orange tinge to it..so im not sure if its the parlon..which came from skylighter..it very light and fluffy..

The 46 grams of parlon took up as much volume as the entire rest of the ingredients?..Passfire says you cant beat this Red!! .

PS.. The Sr(NO3)2 was made by myself from nitric acid and carbonate..the remaining solution was boiled dry.. is it possible that say some calcium left from the evopartion could be contaminating the Flame?.. Not sure how much Calcium would be left i used about 600ml of water. my water is soft

.Are Chorate Reds better..I dont want to use chlorates if possible..But if the Reds are better then i wil go that route..

[adamw]

If you are finding your 'reds' are coming out pink when using SrCO3 try adding more carbon, lampblack for instance.

[Phoenix]

Ruby Red gets discussed on rec.pyrotechnics every so often. I think I remember someone else having the same problem. I can't remember for sure but I think that they found the stars functioned well in the air, despite this. You might want to check that though...

Edited by Phoenix, 29 December 2004 - 06:31 PM.

[burningbush]

If theres any dought about purity of chems used this is probably the culprit.
I had a simalar problem with poor quality strontium nitrate,I got a good batch and the reds were much better!

[chris17]

KClO4 70
Red Gum 10
SrCO3 15
Charcoal 1
Dextrin 4

Is indeed a good formula. However i didn't use Red gum. Instead i used an equal ammount of Arabic gum that i had bought somewhat accidentally. It turns out that the color is very bright. It beats any SrNO3 -red formula i've tried.

Edited by chris17, 31 December 2004 - 12:35 AM.