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Splitting rocks with black powder?

RobHayden's picture

This is a strange one but some of you may know something about it. 

I've got a bunch of large rocks to split.  They are granite boulders in the 500-2500lb range.  So far I've been drilling a series of holes in a straight line, fairly quickly, with a Hilti rotary hammer (very sweet tool), then fitting feathers and wedges in each hole, and tapping each wedge with a drilling hammer until the rock splits, very slowly.  I've been repeating this with each rock until I get manageable pieces then using these to build a dry stone wall.  It's working but very tedious. 

Yesterday someone told me just to use black powder in each hole and set the thing off electrically.  He didn't elaborate on the specifics but I guess you can buy the black powder anywhere.

#1 Does this sound reasonable?

#2 Can it be done without blowing myself or the neighborhood up?  (ie will I have to change my nickname on BT to Missing Fingers)

#3 What's used as the electric spark to ignite the powder?

Any help or advice would be appreciated. Thanks


(post #61090, reply #1 of 24)

>> #1 Does this sound reasonable?


Black powder doesn't have enough oomph to break granite effectively. The construction of the transcontinental railway through the Sierra Nevada in California was delayed for many months by this mismatch. Dynamite is much more effective, but correspondingly more difficult to purchase and use legally.

Black powder is fairly widely available for use in muzzle loading guns, but you'd probably gag on the price of quantities you would need. If you can even buy large quantities in today's security environment.

If you're at all close to the neighbors' property lines, you would need to take steps to reduce noise and flying rock. Even if you did everything right, there's a good chance that at least one neighbor would accuse you of breaking things.

There's a good chance you would need a license to do blasting, which would require time and money for training. Also a good chance that you couldn't buy blasting caps without the license.

>> #2 Can it be done without blowing myself or the neighborhood up?


>> #3 What's used as the electric spark to ignite the powder?

Electrical blasting caps.

My advice would be to rent a tractor mounted demolition hammer.

Edited 5/4/2004 10:05 am ET by Uncle Dunc

(post #61090, reply #2 of 24)

I see that you're trying to re-use the rock, but . . . . I've had pretty good luck in the past with building a fire on top of rocks - it usually splits them.  Not much control on where the split occurs, but the expansion alone is enough to encourage a break. 

You might try a couple of bags of charcoal - it it works, look around for what else might burn !


(post #61090, reply #3 of 24)

You can set off black powder with a hot wire. A few dry cell batteries, an old lawn mower coil and some fine wire.

I wouldn't, though.

(post #61090, reply #4 of 24)

In addition to Uncle Dunc...

Black powder is static sensitive... It could flash in yur face and yur 5th degree burns will be everywhere.

Use the loader mounted breaker hammer and then you have the loader to move the bigger rocks as a plus...

Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming....

                                                                   WOW!!!   What a Ride!

"Some days it's just not worth chewing through the restraints"

(post #61090, reply #6 of 24)


See the following regarding your statement about black powder being static sensitive:


(post #61090, reply #10 of 24)

Now that was worth reading... Thanks....

All I knew about it was from the manufactuer warnings, demo school and working in a munitions R&D facility.... At the R&D facility all but one mishap was attributed to static discharges. Controlling static electricity reduced the number of mishaps there... 

That's what I learned...

Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming....

                                                                   WOW!!!   What a Ride!

"Some days it's just not worth chewing through the restraints"

(post #61090, reply #5 of 24)

Anyone heard of a substance referred to as "liquid dynamite"?

Apparently, you drill holes, put this stuff in, add water, and it splits the rock.

Not sure what chemical reaction is involved.

Anyways, a tool rental store owner was once trying to sell me on it over feather & wedges, but I see nothing related on the web.

(post #61090, reply #7 of 24)

The stuff you are referring to is called betonomite. I've used it on concrete chunks pretty successfully. There is at least one other brand out there whose name presently escapes me.


(post #61090, reply #9 of 24)

Cool.  Thanks.

1 hit on "betonomite".  Think it would work on granite boulders?

Oh, got it- "Betonamit"= 52 hits.

Edited 5/4/2004 4:05 pm ET by csnow

(post #61090, reply #18 of 24)

don't know what it is... but someone is sell'n it on ebay (liquid rock splitter)

(post #61090, reply #8 of 24)

Go ahead try it.

but first change your sceen name to Nofingers!!


Mr T

Happiness is a cold wet nose

Life is is never to busy to stop and pet the Doggies!!

. .

(post #61090, reply #11 of 24)

Don't break them!!!! Move them!!!

I moved this rock last weekend. took me an hour and a half to get it up on rollers then two hours with the family to move it to the front of the house. My guess is that it's 1500 to 2000 lbs.

(post #61090, reply #13 of 24)

Nice boulder, I've got my excavator on the lookout for one like it. One of these days he'll dig one up and then drop it right in the way of my front steps while I'm not home.

(post #61090, reply #12 of 24)

Forget the black powder. It's not a good idea.

The expansive agents work great, and will save you a visit from another kind of agent. <G>

As I recall, the Betonammit is from Spofford, New Hampshire

Here are two more to go with the Betonamit;

Depending on where you live, this might save on shipping costs.

Dexpan from Santa Theresa NM

Bristar, Greenville AL

I've used the Dexpan, it works great.


(post #61090, reply #14 of 24)

Thanks for the info.  I guess I'll stick with the slow but relatively safe way.  This is at a vacation place and I need a project that will take up my time.  It is amazing the knowledge that's out there.  Thanks again.

                                               still got all of my  Fingers

(post #61090, reply #15 of 24)

This is a strange one but some of you may know something about it.  This is a strange one but some of you may know something about it. 

Very interesting thread so far.  I know bentonite as an expansive clay that I use for waterproofing.  Works great.

An acquaintance did successfully use black powder for blasting a lot of rock.  He found a bulk supplier.  Far as I remember, he used the same fuses I used to use as a dumb kid making pipe bombs (10 digits still here!).  His approach was to rest a loader bucket over the explosion to limit the rock shower.  No attempt at cutting or reuse of the stone.

When I looked into a need similar to yours several years ago for a client, my recommendation was an air-powered rock splitter.  Air drill the holes, insert the splitter, pop.  Wish I could tell you it worked great.  Unfortunately, the project never materialized.  That mountain of hand quarried 1'x3'x7' stone is still stacked.

PAHS Designer/Builder- Bury it!

PAHS works.  Bury it.

(post #61090, reply #16 of 24)

Before Nobel, the old Norwegians would drill holes in the cliff sides in the summer, fill the holes with water, and the first hard freeze the rock face would crack off. Patience. Next winter, if you get sub zero F at you vacation spot, drill your holes and fill before you leave, maybe nice split rock next time you return.

When a kid, used flashbulbs or even lightbulbs as ignitors - bust off the glass and a good ignitor results - can one still buy flash bulbs even?  Usually used powdered zinc and sulpher as it was a relatively safe fool proof mix it yurself boom.  Prolly get arrested now.

Once even used a paperclip as an ignitor.  Put a film canister of ZnS in a 5 gal bucket with the paperclip thru it, put it all in a 55 gal barrel, hooked the paperclip across an extension cord, went behind a wall and plugged it in.  About a 1/2 sec delay till the clip got hot and simutaneously tripped the breaker and blew the barrel.  Mom saw the lights all dim, go out, all the same time as a big boom, thought maybe her kid had done something again.

BTW, the Central Pacific did not use dynamite, they had a special chemist on site (forget his name) that mixed up nitro as need for the first long Sierra tunnel - mighty good time made with the nitro vs BP. Hired the chemist after a few shipments of nitro blew up in transit.

(post #61090, reply #19 of 24)

Vietnam story, which aways begins with, " No Sierra, there I was." I graduated from Army Engineer OCS in 1969, where we learned not only how to build war theater buildings and bridges but also how to destroy them with explosives. Det cord, plastiques, poppers, etc. we learned about. As a prelude to this war story, det cord is TNT on a rope that burns at about a mile a second. Wrap it around a tree or bridge support, and it'll cut it cleanly, but you must use a blasting cap (not a fuse) to start it. I was in an air cavalry unit in Vietnam, and the crew chiefs sometimes got bored with our air recon missions, so they would build what they called "super bombs" to drop on our enemy.  Helicopter hydraulic fluid at that time was very volatile, as much as our fuel, so these chiefs might get a gallon can of the stuff, wrap it in C4, put a cap in it with a fuse and throw it overboard on missions. Mostly fireworks, since we were rarely directly over the enemy. But they were amused.

Prior to one mission, on my preflight inspection of the helicopter, I found a "super bomb" behind my intended seat. It was a gallon of hydraulic fluid enwrapped with C4 as usual, but "fused" with det cord, not regular fuse, with a popper on the end. A popper is for fuse, not det cord, but it was scary enough that the chief didn't know the difference between fuse and det cord. Had the crew chief somehow activated the bomb on our mission, it would have immediately blown up, killing all of us aboard. He was punished and relegated from helicopter crew chief to perimeter guard, which somehow didn't make me feel any safer, since he also had a drug problem.


(post #61090, reply #20 of 24)

Right you be:

"Faced with slow tunneling progress, the Central Pacific turned to a controversial and deadly substance: nitroglycerin. Invented in Italy in 1847 and refined in the 1860s by Swedish inventor Alfred Nobel, it was more potent than black powder -- and much more volatile. To eliminate the dangers of transporting it, British chemist James Howden was brought into the Sierras to concoct the explosive substance on site."

"Eventually, the Chinese began to work on blasting the tunnels and the cliff face known as "Cape Horn". As gunpowder was a Chinese invention, little instruction was necessary. "Every boy set off firecrackers on New Year's and feast days and knew the latent dangers that could transform a handful of the gritty gray dust into a lightning bolt" [Howard 230]. They built waist-high baskets out of reeds that would be lowered down the cliff face so that they could slowly chip away at it to make holes for the gunpowder. Each basket had a hauling crew on top of the cliff [Howard 230].

In the tunnels, particularly the 1659 foot Summit Tunnel, it was Chinese work crews who were responsible for the blasting. The rock was so hard that only about seven to eight inches of progress were made in a day. That is, until they began to use nitroglycerin in 1866. With the nitroglycerin, progress was made much faster, but at a greater expense of life. Between the blasting on the cliff face and the blasting in the tunnels, numerous Chinese workers perished. The "Central Pacific did not keep record of coolie casualties" [Howard 230]."

(post #61090, reply #17 of 24)

A few friends of mine have, perhaps had as this has been many years ago, a deep and abiding dislike of a particular structure. A particularly obnoxious and hazardous structure. As a thought project we brain stormed a methodology of damaging the structure without attracting attention.

The solution proposed was to use a cordless drill to drill holes. These would be cleaned and then oven dried wood plugs driven firmly into place. These would then be wet with water with just a touch of soap to aid penetration. Water would be added regularly to maximize saturation.

This alone might be enough to crack the structure but the plan was to work on night well below freezing the idea being that the water freezing would increase expansion and pressure on the surrounding material. If the temperature was not predicted to be low enough dry ice would be employed to freeze the water and increase expansion of the wedges within the hole.

When spalling occurred any cracks or indentations would be exploited in another round until time ran short, to be resumed another night, or the desired effect achieved.

As it turned out these designs came to nothing and the structure was sold and destroyed a year or so later. No structures were destroyed, damaged or otherwise harmed by either myself or any others connected with this brainstorming session. And no this had nothing to do with any anti-development groups such as ELF or any similar agenda.

Another thought would be to employ power actuated pins driven in a line or mechanical expansion anchors, the ones that are inserted into a hole and cranked tight with a wrench. Designed to anchor steel in concrete I have seen them split the concrete quite effectively when overtightened or too close to an edge.

Some though might be given to obtaining a high pressure power washer. The industrial version equipped with a tight nozzle can cut grooves into 60 year old concrete. A groove would further concentrate the stress of any other efforts.

(post #61090, reply #21 of 24)

Use the wire out of a twist tie ,strip off the paper  from the ends and use heavier gauge wire hooked to a car battery or a riding lawnmower battery and it will glow red and ignite the powder. I use to use that method to light my model rocket engines . and since i used to reload my own shotgun shells i know it will light smokeless powder to.


(post #61090, reply #22 of 24)

Or, I wasn't going to bring this up but seeing as that we are into det cord and nitro what the hell, you could do what one guy did. Drill a quarter inch hole. Insert a 25 caliber shell and give it a whack with a ball peen hammer. Can't say he cracked many rocks but it looked like he was having fun. Big SEG.

 A little 'off the hook' for my tastes but no worse than car surfing I guess. The things people do for excitement.

Safety glasses, welders gloves and perhaps body armor and a helmet would be my minimum level of protection. This is assuming the hired help is swinging the hammer some distance away.

(post #61090, reply #23 of 24)

The article on blasting in The Last Whole Earth Catalog featured blasting manuals from the two big explosives manufacturers, Du Pont and Hercules I believe it was at that time. One thing they noted was that both manuals were really remarkably vague about how far one should back off before triggering the shot. So they asked their in house heavy hardware guy and he recommended half a mile as a nice round figure to start with.

(post #61090, reply #24 of 24)


your current method is oner of the best.  You could cut out some of the work by driving a dry wood stake into each hole and then adding water and letting nature (wood expansion) take its course.  It worked for the Romans. 

Assuming you can access the other side of your rock, if you cut a slot the full width of the rock and directly opposite your line of hilti holes, the splitting process will go much faster.  Cut the slot about 1 to 1-1/2 in deep using an angle grinder and diamond blade.  The slot acts to concentrate the splitting force along the desired split line.

Edit:  As I hit POST it occured to me that if it will not disrupt the look you are after, you could split the boulders into really big chuncks the width of your wall and place them directly into the wall.


Edited 5/5/2004 9:26 am ET by ian