Chlorate and Perchlorate Explosives

Chlorate and Perchlorate Explosives

by Dennis Fritsinger

revised 7/29/89

*** WARNING ***

The following material is presented here in the interest of technical enlightenment only. This information, at the time of its writing, is as accurate as the author has knowledge of. This material is the result of years of experience and many hours of careful experimenting. The manufacture, transportation and detona- tion of explosives may be in violation of state, federal or local laws. The preparation and handling of potentially unstable explo- sive compounds is by its nature a DANGEROUS ACTIVITY and mishaps could result in injury or death.

The bottom line is: Always exercise CAUTION when preparing or utilizing these explosive compositions.

FLASH COMPOSITIONS

The chlorate/perchlorate flashpowder described here, if prepared and manipulated with moderate caution, is one of the safest explosives I've dealt with and my preferred choice for a variety of applications requiring a flammable powder explosive, such as salutes, aerial displays requiring a loud report, etc. This explosive can be quite effective when detonated in moderate to large quantities and can be initiated directly by ignition. Its brisance is much greater than conventional blackpowder-type explo- sives when confined.

A) OXIDIZERS

Of the chlorates/perchlorates that I've used, the most stable is the perchlorate group. The most active, but harder to get, is ammonium perchlorate. The least active seems to be sodium perchlor- ate. Potassium perchlorate is by far the most commonly available, although on a couple occasions my supplier has substituted chlorate much to my chagrin, and performs just as well as its chlorate relative. The perchlorates are intrinsically more stable and less reactive. In general, perchlorates are much safer in contact with combustible substances and are relatively safe to use with sul- fur/sulfide compounds. The problem with chlorates and sulfur compounds comes from the fact that sulfur/sulfides can react with chlorates and form chloric acid, which is a rather unstable explo- sive.

B) FLAMMABLE SOLIDS

One of the most important components of flashpowder is fuel for the reaction. It is important that this fuel burn rapidly, as the explosive force is derived from the rapid expansion of gasses from this oxidizing/burning fuel when confined. The best fuels suited for this purpose are light combustible metals and the two best metals I've used are magnesium and aluminum. Finely divided magnesium of 100 mesh or finer is the fastest burning but is more expensive. Pyro or German black grades of 400 mesh or so is almost as fast and at about a third the price per pound.

C) COMPOSITION PREPARATION

The beauty of the basic chlorate/perchlorate flashpowder is its simplicity. There are only two components to blend together, which is a relatively safe procedure providing care is taken to eliminate anything that can produce a spark. Using plastic or glass containers and utensils is recommended. Try to avoid any kind of scraping or fricative activities when mixing or manipulating ingredients. Also very important tips to keep in mind are to prepare flashpowder FAR AWAY from ANY flame or heat source and to take steps to eliminate DUST ACCUMULATION period. Excessive dust buildup is probably the major cause of sudden explosions in both commercial and clandestine firework factories. A slightly humid atmosphere is ideal for reducing combustible dust in the air making preparing pyrotechnics safer. I found that a small room humidifier to be very effective for this purpose.

The chlorates/perchlorates are hydroscopic by nature and are usually rather chunky and need to be reduced with a mortar/pestle. I found that AFTER grinding up the chunks that adding a small amount of the aluminum and mixing it in will keep the chlorate from clumping and retain a flour-like consistency, which is ideal.

I found through experimentation that a ratio of 7 to 3 (seven parts oxidizer to three parts fuel) works most efficiently. Keep in mind that when measuring solid chemicals, the proportions are by WEIGHT, not volume. Get a good lab scale. Using a measuring cup won't get the job done!

Most commercial pyrotechnics using chlorate flashpowder use the basic aluminum chlorate combination and it works well, but improvements can be made by the addition of compounds that will change the oxidation or burning rate of the composition.

Replacing one of the three parts of aluminum with magnesium gives both a brighter flash and a louder report. Also, the addition of a small amount of antimony sulfide, (but no more than 10 per- cent; e.g., with 70 grams of chlorate, use no more than 7 grams of antimony sulfide) will speed the reaction by an order of magnitude. But be VERY CAREFUL because the more antimony sulfide added, the MORE UNSTABLE the composition becomes. Use too much and the compo- sition can explode without any initiation. Adding finely powdered polyvinyl chloride or cellulose based plastic will add smoke to the explosion but slows the burning rate. This can be useful for a variety of applications requiring smoke with detonation such as signaling, special effects, etc.

My general rules when preparing this and the following compo- sitions are to make only small amounts at a time and never keep more than a very small amount on hand. My reasoning is to reduce the chance of an accidental ignition causing a chain reaction type of explosion. The accidental detonation of large amounts of these flash compositions can reduce the average suburban house to splin- ters in a matter of seconds. Minimizing friction, heat or static electricity is imperative!

OTHER FLASH COMPOSITIONS

Here are some alternative formulas that work equally well, but employ some different combinations of fuel/oxidizers. They all share similarities in velocity of detonation, burning rate (bris- ance), sensitivity, etc. Again, proportions are by weight.

COMPOSITION #2

1 to 3 parts --- POTASSIUM PERCHLORATE<br> 1 part --------- SODIUM SALICYLATE, USP, fine powder

COMPOSITION #3

3 parts -------- POTASSIUM PERCHLORATE<br> 1 part --------- ANTIMONY TRISULFIDE<br> 1 part --------- LAMPBLACK<br> 1 part --------- ALUMINUM, DARK PYRO, 400 mesh<br> 1/10 part ------ BARIUM CARBONATE

COMPOSITION #4

3 parts -------- POTASSIUM PERCHLORATE<br> 3 parts -------- BARIUM NITRATE<br> 4 parts -------- ALUMINUM, DARK PYRO, 400 mesh

COMPOSITION #5

60 parts ------- POTASSIUM CHLORATE<br> 23 parts ------- WASHED (NOT FLOWERS) SULFUR<br> 5 parts ------- ANTIMONY SULFIDE<br> 12 parts ------- POTASSIUM NITRATE

COMPOSITION #6

6 parts -------- POTASSIUM CHLORATE<br> 3 parts -------- WASHED (NOT FLOWERS) SULFUR<br> 1 part --------- POWDERED CHARCOAL or SUGAR (my idea)

COMPOSITION #7

6 parts -------- POTASSIUM CHLORATE<br> 2 parts -------- WASHED (NOT FLOWERS) SULFUR<br> 1 part --------- METALLIC ANTIMONY, FINELY POWDERED

NOTE: Compositions 5, 6, & 7 use potassium chlorate in combination with sulfur. These formulas came from an old textbook and are a bit trickier to work with. Use washed or lab grade sulfur, NOT FLOWERS OF SULFUR. Flowers of sulfur is too acidic and extreme- ly dangerous to combine with chlorates. Remember about chloric acid? Blend powders carefully and use immediately. It is probably not a good idea to store these for any length of time.

HIGH EXPLOSIVES USING CHLORATES/PERCHLORATES

An improvised "plastic explosive" can be made from potassium chlorate and, of all things, petroleum jelly. This requires that 90 parts of finely powdered potassium chlorate are blended with 3 parts Vaseline or other petroleum jelly and then mixed with 7 parts of semi-melted paraffin. I found this stuff to be insensitive to heat or shock. If ignited, it burns with a yellowish flame. Howev- er, this mixture is quite effective when initiated with a number 6 or 8 blasting cap. When blasting caps are not available, the mixture will detonate when initiated with a moderate amount of picric acid or mercury fulminate primer exploded by ignition or concussive means. Lead azide or lead picrate can also be used but, in my opinion, they are too damn sensitive. Using this mixture, when confined to a medium density, the velocity of detonation can be expected to fall between 2,925 and 3,180 feet per second, which, in my opinion, classifies it as a high explosive suitable for demolition work. It is a good idea to store it in a airtight/water- proof container.

Here are other mixtures which exhibit similar characteristics. These compositions were successfully initiated using a picric acid detonator electrically fired and using a 10 inch long, 1 inch diameter copper tube for confinement.

COMPOSITION #1A

90 parts ------- POTASSIUM CHLORATE<br> 3 parts ------- HEAVY PETROLEUM OIL (#2 DIESEL)<br> 7 parts ------- PARAFFIN

Packing Density = light to medium<br> Velocity of Detonation is approximately 2,150 and 2,750 FPS

COMPOSITION #2A

89 parts ------- SODIUM CHLORATE<br> 11 parts ------- PARAFFIN

Packing Density = light to medium<br> Velocity of Detonation is approximately 2,480 to over 2,600 FPS

COMPOSITION #3A

90 parts ------- POTASSIUM CHLORATE<br> 10 parts ------- PARAFFIN

Packing Density = light to heavy

Velocity of Detonation is approximately 2,137 to over 3,560 FPS