Rolled stars cracking

[AdmiralDonSnider]

As I´m actually a noob in round star making, I wonder why some of my 5mm chlorate stars on rape seeds cracked while drying naturally, while the vast majority did not...

 

Also, will this present a problem as soon as I try to further coat them, because they´ll fall apart, or will they gain integrity again when sprayed and roll just well?

Edited February 6, 2010 by AdmiralDonSnider

[Bonny]

As I´m actually a noob in round star making, I wonder why some of my 5mm chlorate stars on rape seeds cracked while drying naturally, while the vast majority did not...

 

Also, will this present a problem as soon as I try to further coat them, because they´ll fall apart, or will they gain integrity again when sprayed and roll just well?

 

 

It is possible that the cores expanded from absorbing water. I've had rolled stars crack quite a few times, and same as you only some did it. Just dry them well and continue building them up. I've done that and had no problems.

[AdmiralDonSnider]

Just wanted to add a few infos to make it easier for you to help:

 

- I used Veline Blue with 75/25 water/alc spray

- Rape seeds as cores, never heard that they swell

- rolled them to about 4-5mm, the cracking problem is more severe when the stars are that small

- I leaved them at room temp (20deg or so), no intention to make them "force dry"

 

Please help! Thanks

[swervedriver]

I did the same thing the first time I made veline stars, I rolled them with 75% water/25% alcohol and they never got rock hard, they crushed fairly easily. They also cracked while drying.

 

I suggest rolling with 100% alcohol using the red gum as binder. After doing this, my similar problem went away. I didn't use rape seeds though, that could be the culprit like Bonny said.

 

Those stars are a bitch to light when made round. Super hot kp/red gum prime with at least 10% fine metal, then a slow rough BP green mix rolled over that works.

[AdmiralDonSnider]

I somewhere read that there is a problem with the red gum interfering with the dextrin in case of round stars (due to different drying times), when using both alc and water in the spray; is that possible?

 

Some people seem to suggest the opposite of Swervedriver, using 100% water in the spray...

[pyrogeorge]

i think that the fast drying maybe can broke the stars..

[Bonny]

i think that the fast drying maybe can broke the stars..

 

 

Did you read the earlier posts? Fast drying can crack the stars, or drive in the water, but in Admiral's case he left out to air dry...no added heat (or fan?). They can't really be dried any slower unless you have a room that's cooler than normal room temp.

[AdmiralDonSnider]

Did you read the earlier posts? Fast drying can crack the stars, or drive in the water, but in Admiral's case he left out to air dry...no added heat (or fan?). They can't really be dried any slower unless you have a room that's cooler than normal room temp.

 

And even in this cooler room they did crack.

 

I definately found the cause for the cracks in the swelling of the rape seeds. They do swell no matter how carefully you spray with 75/25. So I tried 50/50 to reduce the water content - the same. I don´t know if they´d also swell in case of red gum or polyvinylbutyrale and alcohol, or in case of parlon with acetone. I also thought about rolling the first layers with acetone to form a layer of plastic which would keep the water out. Don´t know...

 

Larger stars don´t crack (as the swelling isn´t strong enough to crack the thicker layer I assume), but unfortunately I need small stars for bombettes.

 

Any ideas or tricks, other than changing the core? Thanks a lot!

[Ventsi]

I've heard of rolling a thin layer of red gum/ acetone on pasta cores as to not make them expand once rolled with water. I'd say give it a shot and report back, its supposed to work pretty well.

[Bonny]

And even in this cooler room they did crack.

 

I definately found the cause for the cracks in the swelling of the rape seeds. They do swell no matter how carefully you spray with 75/25. So I tried 50/50 to reduce the water content - the same. I don´t know if they´d also swell in case of red gum or polyvinylbutyrale and alcohol, or in case of parlon with acetone. I also thought about rolling the first layers with acetone to form a layer of plastic which would keep the water out. Don´t know...

 

Larger stars don´t crack (as the swelling isn´t strong enough to crack the thicker layer I assume), but unfortunately I need small stars for bombettes.

 

Any ideas or tricks, other than changing the core? Thanks a lot!

 

 

The acetone and parlon idea sounds promising. You could try a thin layer of bentonite (clay). Just enough to coat them and then allow to dry. Even with small cracks, the cores should be OK after that.

Edited February 7, 2010 by Bonny

[scarbelly]

You could cut your small stars for bombettes and roll anything larger.

[AdmiralDonSnider]

I used cut stars for quite a while, but you soon reach some limits, mainly in terms of burn duration. There´s a discussion at rec.pyrotechnics in case you´re interested (entitled tailed stars in bombettes).

I also considered using coreless stars, but I´ll be hard to cut 2mm stars and round them till they reach 3 or 4 mm.

 

In case I roll some layers acetone-based and let dry, I just hope that the water/alc-wet star comp will adhere when I roll further.

 

I´m a bit confused about the swelling phenomenon: I ´d say cores can only swell with water, but others argue that any liquid will make them swell?! In this case alcohol or acetone would have the exact same effect. Can´t believe that...

[FREAKYDUTCHMEN]

Discodip, 1mm cores, don't swell or get sticky, works really well.

[AdmiralDonSnider]

The swelling seeds problem described here is fully resolved by giving the seeds a quick boil before use. This also gives heavier starting cores nicer to work with. It was Karlos who suggested this solution to me and I´m really glad being able to stop rolling at any size now :-).

[Guest no6]

A friend uses tapioca pearls for cores with good success. But we are in a dry climate.

[Bonny]

A friend uses tapioca pearls for cores with good success. But we are in a dry climate.

 

 

I don't think the climate matters,as the cores are wetted when rolling. If anything, I think a humid climate (could) be better as the cores (seeds/tapioca/pasta etc...) would already contain some moisture and would be a bit less likely to swell.

[IACO]

This is a rather interesting, topic to follow, as most are in here, I love the creativity we all bring to finding a solution, i have yet to attempt star rolling, still enjoy the cursing that comes from cutting and pumping:) but could you use candy sprinkles or are they to dissolvable? What about plastic air soft pellets? Though now that I think of it the air soft pellets might be to large.. The ones for my son's guns are 6mm.. Hmm

[dagabu]

Anything that rolls works for cores, sugar and starch based cores can melt or expand leaving you with a mess. Seeds like KNO3 and can sprout (really!). I like to use glass BBs from eBay. They have a hole that the comp fills, they roll nicely and they burn up in flight. There is no lead or other garbage to consider.

 

BEADS

[FREAKYDUTCHMEN]

I Wouldn't roll crackling on these, crackling only needs to be 1.5 to 2.5mm big.

Just start with a dough and a 1mm screen.

[dagabu]

I Wouldn't roll crackling on these, crackling only needs to be 1.5 to 2.5mm big.

Just start with a dough and a 1mm screen.

 

HUH? Cores for stars, not crackle.

[ExplosiveCoek]

I think he misread the topic title . ' crakling stars instead of cracking'

[IACO]

Me thinks your right

[daron]

i use birdseed works really well

[FREAKYDUTCHMEN]

ahhh cracking hehe, yes i thought i was reading crackling, well the message says enough.

[NightPainter]

Would you be wasting your time if you put the cores on an old window screen and sprayed a quick coat of shellac on them ? Edited April 1, 2011 by NightPainter