Pumping Star Compositions

[gizmothegecko]

Hey everyone, I recently got a 1/4-inch, 30-pin star plate and have been testing different compositions for pumping colored stars. However, I'm unsure which compositions work best for pumping.

I had success with the Green Spanish Star formula, adding 5% dextrin and using 12-15% of a 75:25 water-to-alcohol mixture. The stars held together well and performed nicely in a shell. However, when I tried Red Screen Sliced Stars formula (from Skylighter) with the same binding method (5% dextrin, 12-15% 75:25 water-to-alcohol), most of them blew blind—even with a solid step prime.

For binding, I initially added a 10% solution, then increased it slightly until the composition would hold together in my fist but still crumble under pressure.

My questions:

1. How do I determine which star compositions can be pumped?
2. How much water should I use for binding to avoid stars failing in flight?
3. How many pounds of real force should I be pressing my plate at

Side note: After ejecting the stars, the two metal pieces of my star plate (the one with the pins and the one with the holes) get stuck together. It takes me a while to wiggle them apart. I got the plate from CannonFuse.com, but they don’t seem to sell a separating tool. Does anyone know a good way to separate them more easily.

I attached the video of the Red Stars blown blind below:

Edited February 2 by gizmothegecko

[Carbon796]

What is a solid step prime ?

What prime was used, How many layers, What were the steps, How were they bound to the star ? Was the star dry before priming ? Did you allow it sufficient time to dry after priming ? What mesh Mg/AL are you using ?

Why are you using so much alcohol  ? What is the solution your actually using ? 

Ruby red  ( red variant of emerald green, was my go to for red ) It will light easier and has better critical wind velocity. Than the the screen sliced parlon fueled red.

Generally I preferred SGRS or phenolic for pressed color stars. SGRS for metallic streamers and glitter. And dex for more traditional charcoal based larger stars/comets.

I preferred 500lbs of force per square inch across the board. From 1/4" stars to 4" Comets. With approximately 15 seconds of dwell. And a controlled release.

And generally used 5% or less of straight Distilled water, for water bound comps. And straight Denatured alcohol, for phenolic bound comps.

Your plate with 30 pins would be 736ish psi on a PtoF gage. For 500 pounds of force on your star comp.

.04909" star area x 30 pins = 1.4727" x 500 = 736.35psi

Your plates are sticking together ( most likely because your comp is too wet. ) or they are not rotate-able and must be clocked correctly. Did you let the comp temper before pressing ? If you have the machined plates. The chamfer or radius on the bottom of the pins. Looks excessively large. And could be adding to comp migration between the pins and bore. Especially if your comp is overly wet and more " fluid ".

Keeping a spray bottle of water on hand. Will let you clean the residue from the plates periodically.

Generally you want to avoid pressing star comps with large/coarse hard metals. That can bind up and score your pumps/plates. ( there are some techniques to get around this ) And sometimes some AL steamers with an excessive amount of large, fluffy, greasy flake can be difficult to consolidate correctly. Similar to high charcoal ( and large mesh charcoal ) stars they can be quite "spongy " and using less pressure. Along with a stronger and/or more binder. Can usually get around that issue.

Edited February 7 by Carbon796

[gizmothegecko]

I originally used the red star prime from Skylighter, but it didn’t ignite well. Instead, I switched to a step-prime method:

First layer: Monocapa prime

Second layer: Black powder with silicon and dextrin

This worked flawlessly—almost too well. The stars ignited very easily, resulting in a more sparse break, which I actually liked. I’ll be using this step-prime method for all my stars moving forward.

I’m also considering pressing 1/4-inch stars using the Spanish color formulas from Jopetes. However, I’m unsure about the best binding solution. Each formula contains 4% dextrin, 8-12% red gum, and 8-15%parlon, so I don’t know if 5% distilled water alone is enough to activate the dextrin or if I should add alcohol to help dissolve the parlon and red gum.

As for my star plate sticking, I believe it was due to using too much solution. I also didn’t realize the composition needed to temper before pressing. Moving forward, I’ll let it sit for 30-60 minutes to allow the dextrin to activate and for moisture to distribute evenly.

Thanks for all your help!

 

[Carbon796]

Your final layer of prime should be scratched mixed BP components with the silicon and dex. Not a milled BP product.

Neither RG or parlon are binders. Their primary functions are fuel RG and chlorine donator Parlon. Parlon is also not softened or disolved by alcohol. Using higher levels of alcohol along with water. Will start to inhibit the binding power of the dex. You need to choose one binding method to use. Rather than trying to incorporate two different methods that are not compatible.

I would put 60 minutes at a minimum for proper dex activation. It's not just a matter of time for the dex to be properly activated. The comp also needs to be properly incorporated while damp. So the water will be evenly distributed.

[gizmothegecko]

That makes sense. I’ll stick with 5% distilled water to activate the dextrin in the Spanish formulas and see how well it works. Thanks for the help Carbon.

 

[LiamPyro]

So, did you solve the blind red star priming issue? It sounds like you did based on your previous post. If not, I was going to say… based on the video, you can see that the outer prime layer ignites and then burns off without igniting the stars, suggesting that either 1. The inner prime layer is not sufficiently hot to light the star comp or 2. The prime is dry, but the stars themselves are still damp.
 

By the way if you want another red to try, I highly recommend Buell Red. Very good color, brightness, and burn characteristics in my experience. 

[gizmothegecko]

Liam, 

Yes, I did solve the red priming issue. The inner prime layer was not hot enough, so I solve this by replacing it with a Monocapa prime. I just pumped out a batch of Ruby Red stars and I'm gonna test them out in a heading, but I will definitely be pumping out a batch of Buell Red and compare them to see which one I like better.

[All10Fingers]

On 2/8/2025 at 3:01 PM, Carbon796 said:

 

Neither RG or parlon are binders. Their primary functions are fuel RG and chlorine donator Parlon. Parlon is also not softened or disolved by alcohol. Using higher levels of alcohol along with water. Will start to inhibit the binding power of the dex. You need to choose one binding method to use. Rather than trying to incorporate two different methods that are not compatible.

Parlon is most certainly a binder. Use acetone as the solvent and skip the dextrin 

[Carbon796]

If parlon is a binder. Then it could clearly be replaced by any other binder. Dex/SGRS/PR/Starpol/GA/BVA/CA ect. And, still have the formula/star function " correctly ". 

2 hours ago, All10Fingers said:

Parlon is most certainly a binder. Use acetone as the solvent and skip the dextrin 

And, being as the OP is plate pressing stars. Rather than screen slicing or cutting. It is a very poor option. 

[All10Fingers]

Unless it's already an ingredient in the stars he's making