Fence Post Prime - BP substitute

[mkn]

Hi All,

 

I was wondering if I can substitute my milled BP dust for the 65 KNO3 - 12 Air Coal - 10 sulfur ? It looks like the KNO3 and coal have been reduced a touch for the addition of silicon and DE.

 

It seems the only thing that would be different would be the burn speed of milled BP dust verse the mix above.

 

Thanks Matt

 

 

 

[Shadowcat1969]

The milled dust will be "faster" burning than a simple screen mix of the same materials. It might burn too hot/fast in the prime for the prime to be as effective. You can always try a small batch to see.

[Mumbles]

It'll probably work. The formula you have is different than what I have though. I posted the original from Eugene, though it's pretty easy to see where the 12 parts C vs. 15 parts C got mixed up.

 

 

As far as a prime, why not try my ''fence-post prime'' as Eric named it. It burns incredibly fast and HOT. If you up the silicon to 10 parts, it'll even light silver wave stars reliably with no step priming. Come to think of it, I haven't found anything yet that it won't light without step priming - not saying that there isn't a stubborn comp out there - just haven't found one yet.

65 KNO3
15 Charcoal (12 balsa, 3 skylighter or something slower - perhaps pine)
10 Sulfur
5 Silicon powder, 325 mesh
5 Diatomaceous earth, pool filter grade (makes the prime VERY fluffy with lots of surface ''points'')

Bind with whatever you want. I spray 4% gum Arabic solution. This not only makes the prime layer hard as a rock but in regular stars, what soaks in makes them even harder once dry.

[mkn]

Thanks guy's,

 

I just finished 1.75 lbs of 3/8" rolled. I'll give the mill dust a try. Interesting on the 15 coal down to 12. I fairly sure I pulled the 12 from somewhere on this site, my coal is homemade pine so maybe the dust will be slow enough.

 

I guess worse case if they don't light from the gun, I'll have to stop being lazy and mix the prime properly. Just looking to save a few steps with mill dust on hand!

 

Matt

[bigbuck]

i found Diatomaceous earth for sale at tractor supply as use in some type of animal feed, same stuff as used in fence post prime? and can you bind it with dextrin and alcohol/ water solvent?

Edited August 1, 2016 by bigbuck

[pyronoob]

How important is the balsa charcoal?? I can't seem to find a retailer to purchase it. i did find a company in CO to buy balsa shavings and such so i could make my own however shipping seem REALLY extremely high (80 bucks for 24 cu/ft).

[OldMarine]

How important is the balsa charcoal?? I can't seem to find a retailer to purchase it. i did find a company in CO to buy balsa shavings and such so i could make my own however shipping seem REALLY extremely high (80 bucks for 24 cu/ft).

I use Eastern Red Cedar from pet bedding and have had no problems whatsoever.

[pyronoob]

That i have plenty of....been making that all afternoon today. Thanks OM!!

[Arthur]

Especially with primes, the particle size matters and needs to be coarser rather than finer. Screen mixed 75/15/10 works as a prime but milled BP is usually too fast.

[dynomike1]

Patrick where did you find E.

R.C.? Never mind. I was thinking of Red Alder. I dont know where my brain was. Guess i need to look for it.

Edited August 1, 2016 by dynomike1

[Mumbles]

Eugene was pretty adamant about the balsa, but essentially any quick burning charcoal is fine. Using ultrafine balsa dust as a wood source for charcoal was popular a few years ago.

 

As far as the diatomaceous earth BigBuck, its hard to say without a few more details. I believe the stuff that was called for was specifically a pool filter grade. It was relatively fine, but still particulate in nature. I think it was probably a little finer than table salt if I had to guess. It's there to provide a coarser surface to take fire from, and perhaps help hold the slag to the surface of the star. Give what you have a shot. My guess is that it'll work.

[Sparx88]

Exactly. Erc is the only other charcoal that I have tried that performs close to paulownia or cotton. Though being close is a matter of your particular needs.

[bigbuck]

thanks mumbles, found pool filter grade on ebay but have to buy 25lbs as far as a priming ids it ok to bind with dextrin and alch/water solvent?, and I noticed you said no step priming needed so a single layer of fence post should do? thanks

[Mumbles]

Just to clarify something. What I posted in July 2014 was mostly a quote from Eugene Yurek, the guy who developed the formula. I don't have much experience with it personally. I don't believe any prime formula is truly a set it and forget it composition, despite some claims you may have seen. For particularly hard to light compositions, you may need to use a step prime still.

 

Yes, it's fine to bind with dextrin and activate with water or water/alcohol. Eugene was fond of using a dextrin solution in water, as well as using gum arabic solution. There's no reason you can't add a binder to the mixture though. And yes, the 25lb bag size of the filter grade stuff was always sort of a hindrance. I don't know of anyone who resells it anymore however. Try what you have. It'll probably work fine.

[MrB]

It's generally sold in smaller buckets as a adsorbent for stuff like oil spills.. Look in hardware stores. If the particle size isn't good, ball milling should fix that, i suppose. My local suppliers have a bunch of brands, and sizes.

B!

[dynomike1]

Mumbles what are you using for a step prime on Fence post? I was using BP and Silicon but i cant remember how much silicon, and i cant find any notes on it.

[OldMarine]

I use 7% silicon and have had great luck with it. I use the same in my BP prime as well.

[dynomike1]

For some reason i was thinking 8, but couldnt remember. Thanks

[Mumbles]

You may want to use what Lloyd has recommended before and get the surface of the star goo an wet or like slurry and use that to create the step prime. I included the fencepost formula below. I also include some instructions from him given in the past.

 

65 KNO3

15 Charcoal (12 balsa, 3 skylighter or something slower - perhaps pine)

10 Sulfur

5 Silicon powder, 325 mesh

5 Diatomaceous earth, pool filter grade (makes the prime VERY fluffy with lots of surface ''points'')

I might add that there's a technique to applying a prime to hard-to-light

stars. Merely "pasting" on a layer on the outside may not do the trick.

The proper way to do it is to use a common solvent to both the star and

the prime's binding system, then to significanly over-wet the stars

before the first prime layer, so they begin to "slime" themselves in a

dissolved layer of star composition.

To that wet slurry is added an amout of prime estimated to be about 25-

50% of the amount of slurry. With that you've built a mixed layer of

prime and star composition.

Then you begin to apply one or two more layers, slightly over-wet again,

but not to the degree of the first layer.

Finally, apply a layer of prime with the stars only just wet enough to

take it up.

I like, then, to apply a thin but dusty layer of rough hand-made powder

as an outer take-fire layer.

What you've done with all this is to build a step-prime system without

mixing star composition and prime before applying it.

LLoyd

[Maserface]

The method Mumbles mentions is especially effective with the "toro" method, add your final slurry of star composition, then dry prime, then prime slurry, then dry prime.

[bigbuck]

so you actually do make a prime slurry all by itself, i was going to try a 50/50 comp/prime slurry but it does not seem necessary, the stars im going to try and prime are bill ofcas bright white formula from FW database, any one familiar whit a prime method that works on these stars? they seem to be really tough to light

[Mumbles]

I don't actually have much experience doing what Lloyd described. I usually make a stand alone slurry and use that to prime stars. It's quite effective. I use the same 50:50 ratio for my slurries. I apply 10% slurry prime by mass to the stars to start out, and then 5% dry prime (or a second prime for a step) to soak in and dry the stars back out. This can get tricky to explain if I'm not careful. For 100g of stars, I would apply a slurry made from 5g prime and 5g water or alcohol. I add this to the stars and stir by hand (star rollers work too), to distribute the prime evenly, breaking up clumping stars. I then add 5g of dry prime on top of this to complete the prime. For typical stars I do one full layer of pinball, one layer of pinball slurry with green meal dusting (for a step), and one layer of just green meal. This is 30% total prime by mass.

 

I apply it to dry stars, but making the star surface into a slime and applying some dry pinball or whatever your prime of choice is might not be a bad first step to really ensure everything lights.

 

For something very hard to light, I'd want to use a step prime just to be sure. Several primes are capable of lighting comps like the Ofca one you mention, but getting the prime integrated into star comp helps as well. Here's a thread from rec.pyro with Lloyd discussing basically this exact scenario and is actually where my previous quote came from IIRC.

 

https://groups.google.com/forum/#!topic/rec.pyrotechnics/57w-aKXgxqE