Fence post prime?

[Fly]

Mumbles, or anyone can you post what makes up fence post prime?

 

Fly

[dagabu]

Hot Igniter Primes:

Name: Fence-post prime

Source: Eugene Yurek

 

Chemical Name: Parts: Weigh:

 

Potassium Nitrate 65

 

Charcoal Airfloat 12

 

Sulfur 10

 

DIATOMACEOUS EARTH 5

 

Silicon, 325 mesh 5

 

Charcoal, spruce, ball milled 3

 

Tare: Total: 100%

 

 

 

NOTES:

INSTEAD OF ALUMINIUM OXIDE, USE DIATOMACEOUS EARTH!

 

Silicon, unfortunately is one of ''iffy'' maybe it can or maybe it can't be shipped items. Skylighter carries it but won't ship it (pickup only or delivery to selected shoots for free) and I believe Eric has it on his web-page as well (he ''might'' ship). 1# would last a very long time because with the added DE in the prime, it gets quite fluffy even after being wetted with binder so you use a lot less (I'd guess about 1/3 less than a regular prime). And don't go putting down an inch thick layer of the stuff. It seems to perform better with thinner layers around 1-1.5mm even for difficult to ignite stars. If your small test batch won't light don't make the prime thicker - just add a little more silicon up to a limit of 10% maximum when you prime the next test batch. Since you can't ''fix'' a batch of already primed stars, make your test batches small until you find the sweet spot.

 

The formula has been posted to the forum on multiple occasions but here it is again so you don't have to go hunting for it:

 

65 KNO3 (finely powdered or milled - finer the better)

15 Airfloat Charcoal (12 balsa, 3 of anything slower - spruce, mixed hardwoods airfloat, oak, etc.)

10 Sulfur

5 Diatomaceous Earth (pool filter grade not food grade as this is too fine and not garden grade as this isn't steam cleaned and is full of junk and might even be too coarse - any pool supply place would carry it but you'll probably have to buy a 25# bag of it)

5 Silicon powder, 325 mesh dark pyro (up this to 7-10% for really tough to light comps but never more than 10% - 7% is usually enough)

 

Though its probably not necessary, I usually ball mill the meal components for about 15-30 minutes first to get them a little finer and to get them intimately mixed and then screen in the DE and silicon afterwards. Green mixing them also works. I just prefer the short run in the mill.

 

As far as binder, I mix it without one and spray 4% gum arabic. Others have added dextrin or have even put it down with some NC lacquer and all have gotten good results. Basically stick it to your stars with anything you want so long as what you're using burns (hehe).

 

I even prime my shell fuses with the fence-post - into some really thin NC meal slurry (nearly water thin) and quickly into some dry fence-post, wait a few seconds for it to stick and then gently tap off the excess and put the shell aside and keep it from moving around for about half an hour till the NC is dry.

 

Come to think of it, fence-post is the ONLY prime I now use. I see no need for anything else. If it can light stars that are more than 2/3 fine flake AL with ease I see no reason to use anything else. That makes things simple.

 

Let us know what you think.

 

Oh, and do torture test it. Make some hard to light stars primed with it and start shooting them out of your star gun, slowly increasing the lift charge up to say double what you normally use and see if they still light - do for me and from what the guys say, these results are reproducible.

Edited December 23, 2010 by dagabu

[Algenco]

It's never failed for me, as Gene says "it will light a wet fence post in a hurricane"

 

Fly, I have a bunch of DE and enough Silicon if you want to try it

Edited December 23, 2010 by Algenco

[pyroguy1960]

My two cents on this, I've been using a simpiler version of this to prime everything I make, just heating up green mix with silicon. Hobby Chem Supply sells the silicon I use.

 

I've primed everything from perchlorate based /parlon bound color stars to high metal content course flitter streamers with it and it hasn't failed to ignite anything I've made even with the stronger perchlorate based break charges I use now.

 

My method is really simple and fast. Green mix with 5-8% silicon added for the first layer of prime, then green mix alone for the outer layer of prime. My green mix is made with nothing more than commercial airfloat.

 

I also don't use much at all, just enough to coat each layer thouroughly, but not to really build up a thick layer.

 

You ask me all that extra work is totally unecessary, or at least it's not with all the common star formulations I've been using.

[Fly]

Correct me if I'm wrong.But is not silicon just a sand of some sort?If so why does it admit such heat?

 

Fly

[Algenco]

your thinking of silica, silicon is a metal.

In the Prime it work so well because it melts leaving very,very hot globules of molten metal that insures anything it touchs will burn

$8.50lb at Hobby Chem , 1lb will last years

Edited December 24, 2010 by Algenco

[dagabu]

My two cents on this, I've been using a simpiler version of this to prime everything I make, just heating up green mix with silicon. Hobby Chem Supply sells the silicon I use.

 

I've primed everything from perchlorate based /parlon bound color stars to high metal content course flitter streamers with it and it hasn't failed to ignite anything I've made even with the stronger perchlorate based break charges I use now.

 

My method is really simple and fast. Green mix with 5-8% silicon added for the first layer of prime, then green mix alone for the outer layer of prime. My green mix is made with nothing more than commercial airfloat.

 

I also don't use much at all, just enough to coat each layer thouroughly, but not to really build up a thick layer.

 

You ask me all that extra work is totally unecessary, or at least it's not with all the common star formulations I've been using.

 

JMS,

 

You are correct, your version of the hot star prime is an old and well known prime but there are several comps that need even more heat which the DE provides.

[Mumbles]

Silicon doesn't actually melt, it burns forming molten sand. I still question the DE a bit. Some seem to think that it just roughens up the surface for better ignition, where as some seem to think that the micro-pores suck in the molten silica via capilary action to the star surface.

[dagabu]

Mum, I actually use the glass spheres that Tom and I went round and round over last year, they provide the heat I need on a green star and a heavy Aluminum (Lees flitters) star I am working on and while I am no chemist and have no idea what is going on in there, Tom told me that they provide channels for fire and become molten, giving heat to the surface.

 

I have no idea what little dead sea creatures do for prime but Lloyd seems to think they are the cats pajamas and its hard to fight the result.

[Algenco]

Mumbles is correct, the primary purpose of the DE is to provide a rougher surface for taking fire, it will also melt, it's made of silica