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#1 Tim1877

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Posted 27 April 2018 - 08:43 PM

So tomorrow I'm going to attempt to press some stars with one of Calebs mini star plates. I would like to press tiger tail stars that's my favorite effect any advice would be greatly appreciated these are going in 3 and 4 inch ball shells
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#2 greenlight

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Posted 27 April 2018 - 11:30 PM

What size plate did you buy?

I have a 3/8 inch one. I have pressed glitters, red and green rubber stars and just standard perc colours with it. I have noticed that the perchlorate colours burn a little too long for 3 inch shells.

I always wet the composition just enough to granulate it for easier loading of the plate.
I fill all the holes to the top with granulated comp and then place the pin plate on and put it in a vice between two thin blocks of wood. I find that hand tight on the vice makes pretty hard stars.

When dry, they get sprayed with alcohol/water depending on binder used and coated with a thick layer of hot prime to ensure ignition. I found that with a thin layer only half the colour stars ignited.

Also, don't use coarse metals like titanium in the plate as it will wreck it. Powdered magnalium and aluminium seems to be fine though.

Just my 2 cents in case its any help.

#3 Tim1877

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Posted 28 April 2018 - 09:56 AM

I have a 1/4 3/8 1/2 inch plates how do you press the rubber stars
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#4 greenlight

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Posted 28 April 2018 - 10:20 AM

Whoops, I didnt mean to write rubber stars, my mistake haha. I only use the star plate for perc colours and glitters/tailed stars.
I do use the red and green rubber formulas but add dextrin as the binder and just use the parlon as a chlorine donor.

The actual red rubber stars I made only once and were screen sliced like the method on skylighter. They would be much too sticky to press and dry too fast.

Edited by greenlight, 28 April 2018 - 10:46 AM.


#5 Tim1877

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Posted 28 April 2018 - 05:12 PM

I pressed some tiger tail stars today they were super soft when they came out of the plates just wondering if this is normal
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#6 greenlight

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Posted 28 April 2018 - 09:39 PM

Mine are quite soft and slightly crumbly when they come out sometimes because I only use a vice but when dry they are rock solid

#7 Tim1877

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Posted 28 April 2018 - 10:48 PM

Mine were really crumbling wondering if I should let mix sit longer to let dextrin work I use an arbor press put plenty of pressure on the plates
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#8 greenlight

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Posted 28 April 2018 - 11:28 PM

See what they turn out like after drying.
That is a good technique I have heard of too though, letting the mix sit for a while when wet before making into stars.

#9 Boophoenix

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Posted 29 April 2018 - 01:03 AM

I’ve always heard the term called resting I believe. Letting the binder fully activate. I’ll second if ya didn’t get enough force to consolidate the stars the binder can still harden them. I made some experimental core-less PVB stars once that came out like melting gummy worms. I was fiddling with the formula and was worried I may have missed the ratio some at the time and place I was at so I got up at 2am and started a second batch for the next day. If memory serves both ended up solid.

With the charcoal comps hold some pressure on them for a bit they will consolidate a little more often times when pressing.

Best tip I can think of for pressing is don’t over wet your formula when pressing. While I haven’t pressed all that many stars I have made that mistake a time or two.

#10 Tim1877

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Posted 29 April 2018 - 12:44 PM

I don't know but I think I did something wrong when you guys say 5% water that means 5 grams per 100 grams of comp right and the recommended psi is 1800 I pressed to 2500 psi on the PTF gauge
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#11 Baldor

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Posted 30 April 2018 - 01:16 AM

I noticed while pressing wet BP, once you arrive at the desired pressure the first time, the pressure starts dropping fast. I usually pump two or three times again to the target pressure, and every time I let it rest the pressure drop is slower. The wetter the BP, more pronounced the effect. Can be the BP releasing water?



#12 Tim1877

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Posted 30 April 2018 - 09:03 PM

Im thinking about using 50/5/0 water and alcohol to wet the mix wondering if thats enough water to activate the dextrin
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#13 Arthur

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Posted 01 May 2018 - 04:28 AM

With dextrin keep the alcohol content down (zero to 10% works) alcohol interferes with the dextrin hardening and it costs money! Use cool or slightly warm water and let the mix stand in a plastic bag for at least an hour (maybe 4 hours plus) to ensure that the mix is uniformly but minimally moist, then press. Charcoal stars have to be very dry before they are hard, this can take a few days for small stars or several weeks for large stars. Water that's too hot to drink will cause dextrin to set in minutes into rocks that dry over months.



#14 Mumbles

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Posted 01 May 2018 - 07:34 AM

Just to confirm, did you press to 2500 pounds of force as read from the gauge, or 2500 psi on the comp?  I don't know which size of tooling you used, but as an example the 3/8" plate has 30 pins with a total area of 3.31 sq in. That would be 754 psi on the comp.  This might still work, but I'm not surprised if they're crumbly.  If you're going to be pressing on the low end of pressure, you might want to bump up the water content a bit.  The wetter the comp, the better the stars will hold up.  It'll take a little trial and error, but starting around 8% would be my recommendation.  If that's not quite right, keep adding 1-2% water each time.

 

I also am a proponent of letting a composition rest or temper before pressing it.  It's easier to work with in my experience, and ensures that the dextrin is fully activated and the water is evenly distributed.  It really benefits high charcoal stars, which seems to suck up a bunch of water initially and then release it back out more slowly.  30 min is about all you really need, but I know some go as far as letting it sit overnight.  I do all of this in sealable buckets personally.  After mixing it as well as I can, I pack it down into a cake at the bottom of the bucket.  Might just be a superstition, but I've always felt that having it consolidated allows the water to redistribute easier.  


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#15 Tim1877

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Posted 01 May 2018 - 08:16 AM

Im using Calebs mini star plates and it was 2500 on the ptf gauge I'm going to try again today
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#16 Baldor

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Posted 01 May 2018 - 09:39 AM

Then, according to Mumbles advice, you will need about 8200PSI in the ptf gauge. or to be more precise, you need (tooling area / ptf area )*2500. Could you reach this force with your press?



#17 Tim1877

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Posted 01 May 2018 - 03:52 PM

The mini plates only have 12 pins so that is 1865 on the comp and the ones I did today turned out great 8% water shook in plastic bag to distribute water and they pressed rock hard

Edited by Tim1877, 01 May 2018 - 04:00 PM.

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#18 Tim1877

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Posted 06 May 2018 - 06:30 PM

Amazing what 2% more water will do

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#19 zzzybil

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Posted 16 May 2018 - 11:51 AM

 As much as I have read ,  Don't remember seeing anything that notes which particular stars can be cut  vs which are better suited to pressing or pumping or rolling......Maybe someone could EXPAND  on that ......... without a plate - which stars should not be cut ?  Which stars need this big psi pressing ?

 

   I understand rocket motors need  particular pressing pressure .   



#20 Baldor

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Posted 16 May 2018 - 12:27 PM

Some compositions, like TT or Willow ask for a "wet" process to help integrate the KNO3 with the charcoal. 2% water for pressing doesn't seem very wet to me. Could this compositions be pressed with only 2% water, or could be best to add more water, let it dry some, and then press?






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