Fence Post Prime

[tentacles]

Name: Fence-post prime

Type: Prime

Source: Eugene Yurek

 

Potassium Nitrate 65

Charcoal Airfloat 12

Sulfur 10

Diatomaceous Earth 5

Silicon, 325 mesh 5

Charcoal, spruce, ball milled 3

 

Named for it's purported ability to light wet fence posts in a hurricane. The silicon burns and forms molten glass.

 

I don't want to copy and paste the comments from passfire here but I'll try to cover a few bases.. The DE makes this stuff pretty fluffy. Use about 1/3 less than you would with a regular prime. A layer 1-1.5mm thick is all you should ever need. If your stars are ridiculously difficult, up the silicon to no more than 10%.

[Mumbles]

I believe gene seems to tout using balsa charcoal for the airfloat. He thinks he needs the fast speed. My personal opinion is that it doesn't matter. He also uses a grade of DE for pool filters. Not all DE is the same. Crushing it could defeat some of it's advantages.

[qwezxc12]

... He also uses a grade of DE for pool filters. Not all DE is the same. Crushing it could defeat some of it's advantages.

Yeah, I seem to remember him specifically saying NOT to use the food grade DE...the pool filter stuff is coarser and creates the voids that allow the flame to propagate quickly through the prime layer.

 

I now have 20lbs of the stuff (smallest bag at the pool place)...enough to last me forever.

[tentacles]

You can also pick up filter grade DE at some aquarium/pet shops. It's used with various filter apparatus to clarify the water (and they work damn good, too!).

[jadesource]

I believe gene seems to tout using balsa charcoal for the airfloat. He thinks he needs the fast speed. My personal opinion is that it doesn't matter. He also uses a grade of DE for pool filters. Not all DE is the same. Crushing it could defeat some of it's advantages.

 

Mumbles Gene is really sold on the balsa and it is very fast. But i have had good results with both red alder and willow for the fast charcoal he also uses 80% fast charcoal that he ballmills together for about 15 minits or so then adds in the 20% hardwood charcoal when he screens in the DE and SI the 80/20 method has made the prime even better. his thinking was the fast charcoal gets it going quick and the airfloat hardwood sticks around to help the harder to light stars get going . now as to the resons this all works i dont know . All I know is that in side by side star gun tests this prime beats all competitors with hard to light stars shot out of the star gun extremly hard. compared to a strait BP prime even a step prime with BP prime I can add 50% more BP to star gun before it blows blind and in some instances 90% more

[Richtee]

Name: Fence-post prime

 

Silicon, 325 mesh 5

 

Hmm... could actual ground glass be used here ya think?

[Mumbles]

You could probably use ground glass, but it wouldn't be as effective. I'm not sure if the comp itself is capable of melting glass. The combustion of silicon itself probably provides most of the extreme heat needed to keep the combustion products in a liquid state. I'd sooner replace it with a metal than ground glass.

[jameskingama123]

Is this a short review of Fence?

[Algenco]

Mumbles Gene is really sold on the balsa and it is very fast. But i have had good results with both red alder and willow for the fast charcoal he also uses 80% fast charcoal that he ballmills together for about 15 minits or so then adds in the 20% hardwood charcoal when he screens in the DE and SI the 80/20 method has made the prime even better. his thinking was the fast charcoal gets it going quick and the airfloat hardwood sticks around to help the harder to light stars get going . now as to the resons this all works i dont know . All I know is that in side by side star gun tests this prime beats all competitors with hard to light stars shot out of the star gun extremly hard. compared to a strait BP prime even a step prime with BP prime I can add 50% more BP to star gun before it blows blind and in some instances 90% more

 

 

my experience has shown better ignition with less reactive charcoal

[eb11]

have a question about the fence post prime I found some de at home depot not in with the pool stuff but in the pesticids section just wondering if it is the same thing

[Pyrophury]

have a question about the fence post prime I found some de at home depot not in with the pool stuff but in the pesticids section just wondering if it is the same thing

 

I've used diatomaceous earth sold as red mite powder which is probably very similar to what you've found; it's very fine, I'd say about -300 mesh, and slightly buff in colour. It works very well when mixed with silicon in hot primes, creating a porous red hot shell of slag around whatever it's coated on. So presumably you don't need to use the coarse pool filter type stuff for it to work effectively.

[MrB]

Ok, so, tread diving, and digging up an old thread here...

Does it matter if you use calcined diatomaceous earth or diatomaceous earth in our application? I don't think so, but i thought i'd ask, just in case someone had a clue.

This link explains briefly what the difference is. If all we are after is the fluff, then this stuff should work just as well. Seams pool stuff is usually calcined, while food stuff is never, and both supposedly work... Reason for asking. Cheapest source i can find is a hardware supplier, selling it as spill adsorbent. If that works, i should be able to toss it in the ball mill and take it from 0,5-5mm down to what ever i need, and use it, at a cost of next to nothing. (About $1 kilo... Sadly, 20 kilo bag minimum. Guess i know what sort of prime i should be using in the future... Just need 20 kilos of Si)

 

B!

[FlaMtnBkr]

I know the pool filter material is what is called for by the creator. I would think if it gets hot enough for there to be molten silicon then it wouldn't matter much which form it is in.

 

Pool stores should have it for about the same price. Here, even big box stores like Home Depot have it.

[Mumbles]

I'd imagine he meant he needs an equal quantity of silicon for Fencepost Prime. It contains both DE and silicon. But yes, if you can make a prime that manages to melt DE, you're probably is pretty good shape for lighting the star.

 

I'm of the opinion that the DE primarily provides a rough surface to help light the star and perhaps hold the combustion products on the surface of the star. There are other claims about it's function that are, in my opinion, less substantiated. In either case, both types of DE should be suitable. I do wonder about the effectiveness of ball milling it however. You ideally want something relatively coarse. It's unclear how the microstructure of DE plays a role. I guess there's only one way to find out. Worse case scenario, you can use it as a bargaining chip to try to get a pool.

[MrB]

Relatively coarse, sure, but, 0.5-5mm is quite large. I'd imagine the 0.5-1mm range would work fine, so screen, mill, screen, and so on. Weird thing is... I cant even seam to find DE as a pool filter supply around here. Checked hardware stores, and pool suppliers / builders. But as adsorbent, they toss it after you. That means i cant even get a price quote, but then again, the adsorbent isn't really costly, so no worries.

B!

[pex]

I have a question. About the silicone

is this a metal powder? because there is alsow. A silicone like plastic.

 

Thanks allot

 

Pex

[FlaMtnBkr]

We use silicon in pyro which is a metal, usually in primes. There is silicone which you can caulk your windows with. This isn't used except as the binder/fuel in a blue strobe rocket designed by Doc Barr (I think?).

[psypuls]

are the ingredients in this prime milled, or is only the kno3 milled and then you screen everything together 10 times perhaps?

[MrB]

Ball mill the "BP", add DE, and silicone through a screening process. It's my understanding that especially the DE is there for the "texture", milling it would be counter productive to some extent.

The odds of DE and / or silicone sparking, and setting of an explosion seams low.

B!

[psypuls]

why do some people screen the mix and other ballmill it?

[Seymour]

It's the same as Charcoal stars such as tigertail, it really comes down to personal preference.

 

Some people buy all chemicals pre powdered and have access to commercial BP and do this hobby with no ball mill. Others do have a mill but consider screening the powders to create a superior product, and perhaps also want to limit the amount of live milling they do. Believe me, while I willingly ball mill BP, even mills considered 'safe' occasionally explode and it can be very destructive.

 

Prime is best if it's not too clean, because a bit of slag being produced can help hard to light compositions light, or less hard to light ones at high speed, and so on.

 

However other people simply find it easier to mill the BP components, perhaps because they don't have pre powdered potassium nitrate, or because they find it easier to mill the KNO3, Charcoal, Sulfur and binder for half an hour or so, and then screen the rest of the components in afterwards, and if screened prime is better than ball milled primes, that does not matter at all if the ball milled prime reliably lights the stars.

 

What matters is that what you do works for you, and is safe (or as safe as making explosives can be).

[psypuls]

well that helped with explaining on some of the reasons and gave me a good insight, but still couldnt make up my mind as to what my personal preference would be.

I mean which method is really the best for hard flash breaks? screened fencepost or 30min ballmilled- screened fencepost sorry to be a nuisance

Edited October 26, 2015 by psypuls

[Mumbles]

To determine a personal preference, you probably need to try both out for yourself. I always milled at least a little bit, since most of my hotter BP chems were coarse.

[Ubehage]

why do some people screen the mix and other ballmill it?

Screened and ballmilled compositions tend to be worlds apart in performance.

Ballmilled BP will burn much more rapidly, with little or no residues left behind. Whereas screened compositions will most often burn slower (slightly slower or much slower, depending on the screen-#), and also often tends to leave residues behind.

[memo]

making fence post prime i wonder if you could sub borax for silicon. i have used borax as a flux for melting metals. it lowers the melting point and turns to glass when cool.

 

memo