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Best additive for BP


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#1 dannytsg

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Posted 05 May 2013 - 05:39 PM

I am just after some advice from the experienced members about what is the best additive to go in a typical 75:15:10 BP mix.

I have read that dextrin as a binder helps and I have read many different things on whether water/alcohol should be added.

Please can I ask for some comments or tips as to what works best for you. My aim being to increase the burn rate of a standard dry 75:15:10 mix.

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#2 barnsley-mark

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Posted 05 May 2013 - 08:00 PM

The dextrin, water and alcohol if used are for Corning, or granulating the finished BP.
Granulating (Corning or ricing) increases burn speed due to surface area and air gaps etc.
Depending on use, you don't always want very fast BP
Added alcohol or water etc. is fully evaporated during drying so does not add anything to burn.

Edited by barnsley-mark, 05 May 2013 - 08:02 PM.


#3 felixthecat

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Posted 05 May 2013 - 08:09 PM

hi danny....ive had great sucess with 10% dextrin and 1-4 isopropyl alchohol/water mix,added a a few ml at a time to

50g batches mixed in the ziplock bags my chems are supplied in,u need to take your time kneading the water in untill u have a dough that can be spread on a sheet of tinfoil roughly 5mm thick,,,after this dries for a few days u can easily break it into granules with a plastic spoon under your thumb..i dont bother to screen different sizes this works in my 3`` mortar and mines a treat,,,take care dan



#4 dannytsg

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Posted 05 May 2013 - 08:30 PM

Thanks for the replies.

@Mark - could you please explain the difference in slow-fast burn and what applications a slow burn or fast burn may be used in?

Thanks in advance

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#5 barnsley-mark

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Posted 05 May 2013 - 09:10 PM

There are huge topics on here specifically on BP. I don't add alcohol, just dextrin and water to make a dough and then pushed through a kitchen grater and left to dry on news paper.
Fast BP is required for rapports (noise) and break charges in shells.
Lift charge can be fairly poor or slow burning and still make lots of gas and therefore good for lift in a mortar.
In special effects I often use commercial BP (for cannon and muzzle loading guns) and this can be surprisingly slow burning.
Break open a shotgun cartridge and test burn the charge from that - very slow but makes fantastic lift.

#6 dr thrust

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Posted 05 May 2013 - 10:10 PM

Fast bp for nozzle-less rocket motors, the best additives being the choice of charcoal, ( willow for example) the other additive being time,milling time that is, the more you mill the faster it gets

#7 digger

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Posted 05 May 2013 - 10:17 PM

Fast bp for nozzle-less rocket motors, the best additives being the choice of charcoal, ( willow for example) the other additive being time,milling time that is, the more you mill the faster it gets

 

Yep as above. Commercial black powder is just variants on KNO3, S and C, no binder is used as it is the processing technique that produces the appropriate grains. For motors as the Dr suggests no binder is required.

 

If making BP using a wet corning technique then 1% -  2% dextrin may be added during the milling process, any more has an effect on the oxygen balance and hence slows the powder down.


Edited by digger, 06 May 2013 - 07:23 AM.

Phew that was close.

#8 dannytsg

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Posted 06 May 2013 - 07:08 AM

Interesting. I appreciate the replies.

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#9 digger

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Posted 06 May 2013 - 07:22 AM

P.S. With the alcohol water mix. The alcohol is only there to break the surface tension and help the wetting. It has no other purpose, in fact it does not activate dextrin in any way, it is the water that makes the dextrin bind.


Phew that was close.

#10 dr thrust

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Posted 06 May 2013 - 11:00 PM

Now then Corning , one method is pressing your bp and a little moisture in a die to produce a "puck" which Is then Broken up in different sized grains depending on what your doing.
The idea is to aid flame propagation , quote" The spread of a flame in a combustible environment outward from the point at which the combustion started."

the flame can get around the gaps in between the grains much faster than a pile of bp burning downwards.
Interesting enough the fast bp needed for nozzle- less motors has to be a controlled but fast burn rate ,too fast and the rocket explodes, so mineral oil is added to get a constant- ish lol burn rate.
The same principle applies to magnesium and aluminium fuelled flares without the desensitiser and burn rate control of the oil,paraffin wax, etc you'd basically have a flash mix in a tube

Edited by dr thrust, 07 May 2013 - 05:45 PM.


#11 dannytsg

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Posted 07 May 2013 - 08:30 AM

So ideally based on what's been posted thus far, wetting the powder, letting it dry and then putting it through a strainer/mesh is the most efficient way to get a faster burn out of the standard green mill BP made for experimentation. The composition of the wetting I.E water or water&alcohol is really down to personal preference as opposed to it being a necessity for a faster burn?


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#12 digger

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Posted 07 May 2013 - 10:51 AM

OK as the Dr says. The proper method of corning is pressing the mix in a die with less than 6% water in the mix. This produces a rock hard puck that can be dried, smashed and then sieved to get the appropriate grain sizes. Commercially this may then be polished with graphite (but not always).

 

The other method often employed by amatures is to dampen the milled ingredients (which includes a small amount of dextrin in this case) with water (alcohol in the water helps wetting initially but does not add to the final strength of the grains so in fact there is no need to use it) with water and then push it through a sieve to create grains which are then dried.

 

However this topic has been well covered on the forums before, so I suggest that you do a bit of a search and you will dig out  a great deal of information.

 

D


Edited by digger, 07 May 2013 - 10:54 AM.

Phew that was close.

#13 cooperman435

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Posted 07 May 2013 - 11:05 AM

To add a little theory of mine...............

 

Reliability is the main aim, for pyrotechnic use a very powerful BP can help but a slightly slower one is 100% fine as long as its the same every time.

 

For this I personally advise a routine and this one worked for me in the past very well:

 

75:15:10:2 ratios weighed out in the same total weight every time and with roughly the same grade product (for me this was crystals of Nit, willow charcoal that passed 4#, powdered sulfur and powdered dextrin, the total weights will depend on your mill capacity)

 

Mill it properly, in a correctly charged jar for the same time duration, (jar 1/2 full of lead media, composition filling the spaces between the media, and the same length of milling time every time)

 

I then sieved out the mill powder, and wet it with 2/3 water and 1/3 meths mixed together until it JUST starts to clump into a dough ball (I recommend the mix of water and meths as you need more water than is good for the mix to make it clump, too much water dissolves the nitrate and can (in my opinion) undo some of the milling when it recrystallizes)

 

I then grate it through a cheese grater, allow it to dry, crush it a bit by hand to break up any stringy bits and grade it with sieves.

 

A very fast product and very easy to process.

 

 

BUT nothing you do will replace the proper milling process to gain proper burn speeds.

 

2% dextrin is more than enough to harden the grains too



#14 dannytsg

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Posted 07 May 2013 - 12:17 PM

Thanks for all the replies. I will try to incorporate this with my next lot of testing


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#15 dr thrust

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Posted 07 May 2013 - 05:55 PM

Talking about black powder die's is there a optimum size or does it depend on how big your press is, I want to turn one as I have some 101 mm dia 10 mm thick walled tube with a internal dai of 82 mm, to much?
A few I've seen are around 75 mm plungers and downwards would it be unreasonable to have a plunger size of 60mm diameter ?

Edited by dr thrust, 07 May 2013 - 05:56 PM.





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