“Hot Nitrated Charcoal” Stars Problem

[LiamPyro]

I attempted to make a “simple” batch of Chrysanthemum 6 cut stars using the “hot nitrated charcoal” method posted by Ned in which the KNO3 is made into a nearly saturated boiling solution, then added to the dry ingredients and formed into a patty in a plastic bag. For 350g total batch mass (192.5g KNO3) I used 85g water (78.5g is the theoretical minimum at 100 deg C for this amount of KNO3) and brought it to a boil, adding sufficient water to maintain the 85g after evaporative losses. 
 

After adding the dry chems and stirring, the paste began to thicken, and was stirred until the temp dropped to ~115 deg F then placed in the ziploc. Unfortunately, upon further cooling, the putty never solidified even though it became increasingly stiff. It turned into a sort of non-Newtonian fluid from hell! I even removed it from the bag and dried it somewhat before re-forming it, and despite being hard to the touch and requiring some force to cut through, the stars would slowly “melt” back together when allowed to rest long enough. Oddly, in this state, the star mix could be “crumbled” like a dry dough but would still exhibit fluid properties. I riced it through a screen, dried it more, then re-wet it with 75/25 water/alcohol and was finally able to get rid of the non-Newtonian fluid behavior and cut it into stars.

 

How does one avoid this problem? Is it necessary to prepare an exactly saturated (or even super saturated) solution to keep water to a minimum? Should I have included some alcohol to modify the surface tension of the water? Does the mixture have to be kept hot once mixed to allow more evaporation to take place?

[Carbon796]

A simple batch of C6 would have used RT distilled water and Dex. 

As with most things that people like to over complicate with Pyro. Your probably going to have to. Fine tune it on your end, for your materials. The materials that Ned used at that point in time. Are probably not exactly what you have on hand currently. For example.

Iirc, I believe that the nitrate soaking into the pores of charcoal myth. Was disproved awhile back.

[LiamPyro]

Yeah, you’re right. I said “simple” because the method is supposed to be straightforward and non-messy, at least the way Ned shows it. Maybe I should take this as a hint to truly keep my processes as simple as possible… 

 

If you have a link to the nitrate soaking into the charcoal pores being a myth thing I’d love to read it. This one’s been bugging me for a while!

Edited Sunday at 06:23 PM by LiamPyro

[Carbon796]

I don't, my assumption would be that I saw it on FWing. There was that guy that was analyzing metal particle shapes/sizes/mesh averages. That you could also send samples to. To have analyzed for a nominal fee. It may have been him. Or someone else that posted a document . . . from . . . Somewhere  . . . It's probably been almost a decade, since I recall seeing it.

I wasn't necessarily saying, you should keep things, overly simple. And not experiment. But often times. The traditional/time tested methods are faster and more reliable. Without an excessive amount of testing/tuning necessary. When your trying to actually get stuff done.

 

[DavidF]

A newbie once asked (on Passfire?) if they could make firework stars without any equipment like a ball mill. I theorized that it would be possible to make a supersaturated potassium nitrate solution in hot water, add the other ingredients, cool the mixture, make a dough, and cut them. Of course, I was thinking of charcoal stars. I chose Bleser's blonde streamer stares, which are basically C6 with added FeTi. It worked, but I did it more out of curiosity than anything. Years later, Ned picked up on the idea and tried it. Next thing, he's making videos about it, and testing 12" shells with this kind of stars! He came up with a 'formula' that spec'd using 88% of the charcoal weight as water. I'm not mentioning this in a 'sour grapes' way. Ned 'credited' the idea to me. Thing is, I just suggested it as an outside the box idea for beginners, not as something that was in any way better than accepted methods. One drawback is the fallout that these stars can produce if not made 'just so'. A lot of folks like that 'effect', but I think it looks dirty. Fallout is greatly reduced when the sulfur and charcoal and binder are well-screened together. Also, IIRC, the 'pot-nitrated charcoal' is a different thing that Ned came up with separately from this method- I think. 'C6 extra' comes to mind.

Fast forward, the best attribute to my method in the end was the bag! Ned ended up calling them 'baggie stars' but that's a bit of a misnomer. I use Ziploc Brand Freezer Bags. I also use the bags differently than Ned does. Ned uses dowels beside the bag as spacers to roll the patty to a specific thickness. I don't, and I disagree with doing it that way. I roll the patty out so that it slightly stretches the bag, being careful to not pop the zipper open. I've described it on this forum a few times. I also found that the bag method for cut stars is ideal for small (1 KG) batches of cut parlon stars. Past wisdom was that parlon stars can't be cut with a knife because they are too sticky. It's easy if it's done right, also discussed on this forum a few times. I've made lots of them this way.

In the beginning, the success of the pot o' goo star making method was attributed to the use of SGRS as binder. SGRS is a much more forgiving binder than dextrin when it comes to cut stars 'slumping'. There was a guy named Eugene Yurek that went on and on and ON about SGRS as a binder for charcoal cut stars, so I tried it. It worked just like Gene said it would. As time went on, I tried the bag method for cut charcoal stars using dextrin instead of SGRS, and also using room temperature water. Both methods worked. Of course they worked, that's the way they've been made for a long time! I still maintain that SGRS is more beginner friendly than dextrin when it comes to slumping. My favorite stars to make with the bag method are willow diadem stars. I make 1 kg. batches at a time, using commercial airfloat charcoal. If memory serves, I use between 300 and 330 grams of water per batch. If I have over-moistened, I can 'rescue' a batch by putting it in the fridge for a while to stiffen up and then cutting the stars on a cold aluminum slab. The stars are primed with scratch mix when cutting. They should NEVER be put in the sun! The solubility of the nitrate goes up with temperature, and the stars slump. They should be dried cool, maybe even with a fan blowing on them. My WD stars are as hard as rocks in a couple of weeks. I made these ones this way:

All the color stars were parlon stars, also made with the bag method.

[Mumbles]

85g for 350g of charcoal composition (24%) doesn't seem outrageously high for patty cut stars. When you say slumping, do you mean they didn't maintain perfect cubes, or do you mean they were fusing back together? I've made a lot of cut stars by this method. As long as they're not totally fusing back together you'll be fine. They might not drop off the paper as a thousand individual cubes, but they can usually be pretty easily broken apart with a hand full of stubborn ones after drying for a little while.

If you're looking to decrease the water, it's worth noting that it's more soluble than you're probably giving it credit for. I'll see if I can find a good one, but you should know that any solubility figure or curve you find that stops at 100C is incomplete. Boiling, fully saturated nitrate solution is probably closer to 115-120C and probably has 30-40% more nitrate dissolved in it.

For what it's worth, I've also seen information claiming that no nitrate is dissolved into charcoal pores. Very similar to Carbon, I have no recollection as to where I saw that or any concrete support to back that up.