Pumped vs. cut stars

[dangerousamateur]

Hi there,

 

I never did anything other then cutting.

 

When you compare the same mixture with cut and pumped, wich one is stronger, more flashburst resistant?

And wich one is denser(I assume the pumped one of course, but what are your experiences)?

[warthog]

Pumped stars would be denser but I have no scientific proof of this, only the thought that you use some pressure to consolidate the damp comp before ejecting it from the pump. I would also therefore wager they are stronger as well, again I have no real proof since I rarely cut stars.

 

I routinely use a star plate and hydraulic press to make my stars and when I make shell I do use a nitrate/sulfur/Bright Al Flash booster along with 4:1 BP coated rice hulls. I don't recall having any stars disintegrate on break yet so it must be OK at least for me.

Edited April 21, 2012 by warthog

[Potassiumchlorate]

Pumped stars are denser, yes. That's why pumped barium chlorate stars by Lancaster and Hardt contain 28% potassium chlorate. I don't like to mix in potassium compounds in my barium chlorate stars, though. They're to precious for that. Instead I'm now making them smaller and using red gum instead of shellac to increase the burn rate without impuring the colour more than very marginally.

[warthog]

I press my "pumped" stars and comets with a hydraulic press with varying PSI depending on the size of the output and also whether I am using a star plate or a single star/comet pump. I also make sure to have a dwell time of a minute or two to ensure that the pressure is nice and even so that the stars/comets come out uniformly dense for each composition so that the performance is more easily repeatable. I also weigh the amount of comp to put into a comet pump in order to make a comet of a certain length, again to aid in repeatability.

 

I just fill a star plate with as much as I can easily stuff into both sides of the bottom plate. Then I push the pin plate into the hole plate a bit and press it to the proper PSI for the size of star and again allow the pressure to dwell for a minute or so before using the spacer bars to trim the stars to length. Then out of the plate and into the prime for a quick dip then onto the drying screen to dry. Once they have dried I then fully prime the stars with the proper solvent ad prime and back onto the screen to dry.

 

Contrast this to cutting, which I do by making a patty of the proper thickness, dusting with prime, turn it over and dust with prime again, then cut into cubes and dust with more prime. After they are all cubed up, into a bowl with a spritz of solvent and a shaker of prime and coat with prime until done then onto the screen to dry.

 

Certainly it is easier and faster to make cut stars. If I made a lot of cylinder shells (which I am not ruling out doing in the future), I might cut stars more often so I could make a lot of them quickly. I make ball shells though and until I get the hang of rolling stars, pumped stars fly better, fit easier into the hemis and hold up better to the hard breaks than cut stars do in my experience which is extremely limited for sure.

 

I also like the way pumped stars look in process. Cut stars look kind of amateur to me (I know that many professionals make a lot of cut stars it is just my opinion, OK?). Meanwhile a pumped star looks like a nice, neat little pellet that you might find coming out of a factory. So on top of all the above reasons, durability and flying better etc, I like how pumped stars look as well.

[dangerousamateur]

I press my "pumped" stars and comets with a hydraulic press

Uhhh... thats something else

 

I would pump with a simple little star pump or a syringe.

I wonder if this method pays of in therms of density and strenght compared to cut stars.

[californiapyro]

same method, just a different tool. all of his information still applies

[dangerousamateur]

Hmmm OK.

 

I did some syringe pumped stars yesterday Bound with 5% dextrine only. They're not entirely dry, but I find them extremely weak.

How wet do you make your stars to pump? Mine where just right to granulate them with a sieve, maybe a little wetter. Is that enough to bind properly?

 

Maybe it's because dextrine sucks as a binder... My cut C6 stars mostly often crumble in slowflash broken shells too.

[Potassiumchlorate]

About +10% water by weight. It should be 25% alcohol (by volume will do) in the water. You should also press hard when pumping.

[dangerousamateur]

You should also press hard when pumping.

I did. Tortured the syringe until it bent.

 

I wonder if commercial metallic star pumps are much better? Obviously they are also not build for extreme pressures.

Sometimes I'd like to whack the stuff with a hammer to compact it really good.

[Potassiumchlorate]

I did. Tortured the syringe until it bent.

 

I wonder if commercial metallic star pumps are much better? Obviously they are also not build for extreme pressures.

Sometimes I'd like to whack the stuff with a hammer to compact it really good.

 

If the dextrin is activated, you should only need hand pressure. Commercial hand pumps are pretty good.

[dagabu]

I press Wolters 1" crossette pump to 10,000 all the time with a certain comp and there is zero distortion.

 

-dag

[bob]

Hmmm OK.

 

I did some syringe pumped stars yesterday Bound with 5% dextrine only. They're not entirely dry, but I find them extremely weak.

How wet do you make your stars to pump? Mine where just right to granulate them with a sieve, maybe a little wetter. Is that enough to bind properly?

 

Maybe it's because dextrine sucks as a binder... My cut C6 stars mostly often crumble in slowflash broken shells too.

this sounds like your dextrine has something not right with it

I have not made cut stars only pressed and rolled

but my rolled stars are to hard to deform by hand right after there done and you can stomp on them when there dry (not with shoes)

my pressed are quite soft when there wet but after a day or two they harding right up! (I used a large vise to press them so I could get a little bit of presser on them)

maybe I'm way off on this tho (as you all know I'm a newbe)

Edited April 29, 2012 by bob

[Potassiumchlorate]

Rule of thumb: if an adult man can crush a star with his bare hands, the binder is too weak.

[dagabu]

Rule of thumb: if an adult man can crush a star with his bare hands, the binder is too weak.

 

A dry star that is... Interestingly enough, every comp seems to react differently to the binder and the technique one must use to form them. I have a favorite willow star that I really love but it cant be rolled or cut and pumping it takes a careful hand, too little pressure and it crumbles out of the pump and too much and it fractures.

 

One thing I found works the best is to not add the dextrin as a dry ingredient but to dissolve it into warm water, filter and spray it on the dry comp. I think this was a Passfire (EY) member that posted this again last month that came up with the idea.

 

-dag

[warthog]

I have been known to give my pumps a rap or two with a raw hide hammer to achieve compression. Not like I was pounding in a nail mind you but a decent rap with a raw hide hammer works well for me at least and can gives me a pretty nice star too. I can't give you a percentage of water for the wetness but I will simply tell you what I have done:

 

I put the comp into a tub then using a spray bottle add water with 10% alcohol until I get what aI want in there, then I stir it up really well and put a lid on the tub and leave it for ten minutes or so so the dextrin will activates well. Next I screen it a few times to get the water better distributed and see if it is the right consistency. I usually need to add a little more water at this point because I tend to try and add as little as I can and sort of "sneak up" on the right amount. Then I screen it a couple more times and let it sit again for a bit, then one last time through the screen and then I start pumping once I get the moisture to a point where I can barely make a ball out of the stuff but there is no easy way to squeeze water out nor does it show a water sheen to it when I make the ball.

 

Again, take that for what it is worth... nothing but my opinion.

Edited April 29, 2012 by warthog