How do I hollow out a rock?

[+Puppy Dawg]

Seriously how.

[+Chrysalides]

Seriously how.

Shaped charges?

 

I guess it depends on the rock and how large a hole.

 

Might be easier just to create a fake shell using concrete.

[knowschad]

Seriously how.

 

Totally depends on what kind of rock. Some types of sandstone might be fairly easy. Gypsum and soapstone can be carved easily with a knife. Granite, take it to a headstone company.

 

I recently drilled a hole in some limestone using a mansonry bit. It wasn't too difficult, but trying to drill a bunch of holes next to eachother and chiseling out the rest (like you might to to hollow out a log) would have been very tough.

[+StarBrand]

To quote from a movie.

 

geologic changes take "time and pressure" - drip sand and water on it (for long enough) and you'll have a hollow.

 

 

 

(bonus points if you can name the movie....)

[+Puppy Dawg]

Or maybe...

[+Kit Fox]

To quote from a movie.

 

geologic changes take "time and pressure" - drip sand and water on it (for long enough) and you'll have a hollow.

 

 

 

(bonus points if you can name the movie....)

 

Shawshank Redemption?

 

 

I did it the "manly way" (only because I didn't have a rotary percussion drill.) I used a 3lb mini-sledgehammer, and a set of 100 year old Star drills. It took me hours and the cache stumped many cachers until I unchecked the "for Premium members" box, and the cache was quickly stolen.

[+wkmccall]

Seriously how.

 

Not sure about the Manly way, but the smart way would be to make something that Looks like a rock......

[+bittsen]

Get a coring drill bit. Use a drill press and go to town. When you have the depth deep enough, drill a hole in the mddle of the core and use explosives to dislodge it all. (You can also fill the center hole with water and run through a few freeze/thaw cycles)

[+Gitchee-Gummee]

Depending on size of the rock, etc., you could take it to a local lapidary (rock shop) and ask.

Be prepared to pay tho, it's their living ya know.

 

It is possible too, that a gravestone (monument) company could help you (don't bet too much on that, they are already plenty busy enuf).

 

Best method is a water cutter using abrasive. Can be adjusted to cut through, or just into, or anything in between.

 

Better yet, buy one and go into business! $2,500 - $10,000 depending on size/features (hence you see why you get to pay for the service, eh?)!

[+Stunod]

I hope you're gonna put an ammo can in that hollowed-out rock. You know...to go along with your sig line and all...

[+mrbort]

Get a coring drill bit. Use a drill press and go to town. When you have the depth deep enough, drill a hole in the mddle of the core and use explosives to dislodge it all. (You can also fill the center hole with water and run through a few freeze/thaw cycles)

 

As a geophysicist specifically trained in geomorphology and continuum mechanics, I seriously doubt that the freeze/thaw method would work. The ice will not create internal pressure but instead will escape upwards through the opening rather than the path of greater resistance of forcing the rock apart. Even the freeze/thaw cycles in normal weathering that were once regarded as a solved problem are now being reexamined as far as the expansive force goes on a macro scale. It seems that the micro-scale freeze/thaw cycle is much more effective.

 

The answer to the original question, as others such as Chad's Pal have noted is dependent on the type of rock. If you have a fairly cohesive yet soft rock like pumice, you should be able to core it out fairly easily using tools you probably have around the house. Other types of rock can be much more difficult. What type of rock are you planning on hollowing out?

[+NYPaddleCacher]

Seriously how.

 

Totally depends on what kind of rock. Some types of sandstone might be fairly easy. Gypsum and soapstone can be carved easily with a knife. Granite, take it to a headstone company.

 

I recently drilled a hole in some limestone using a mansonry bit. It wasn't too difficult, but trying to drill a bunch of holes next to eachother and chiseling out the rest (like you might to to hollow out a log) would have been very tough.

 

I did the same for a puzzle cache I adopted that was based on meteorites. The original container was a waterproof match stick container with some earth magnets attached but it was muggled. I replaced it with a rock that looks a bit like a meteorite and just used a masonry bit to drill a hole large and deep enough to hold an aluminum pill container (like a large bison tube). It probably took 30 minutes or so to complete the container.

[+bittsen]

Get a coring drill bit. Use a drill press and go to town. When you have the depth deep enough, drill a hole in the mddle of the core and use explosives to dislodge it all. (You can also fill the center hole with water and run through a few freeze/thaw cycles)

 

As a geophysicist specifically trained in geomorphology and continuum mechanics, I seriously doubt that the freeze/thaw method would work. The ice will not create internal pressure but instead will escape upwards through the opening rather than the path of greater resistance of forcing the rock apart. Even the freeze/thaw cycles in normal weathering that were once regarded as a solved problem are now being reexamined as far as the expansive force goes on a macro scale. It seems that the micro-scale freeze/thaw cycle is much more effective.

 

The answer to the original question, as others such as Chad's Pal have noted is dependent on the type of rock. If you have a fairly cohesive yet soft rock like pumice, you should be able to core it out fairly easily using tools you probably have around the house. Other types of rock can be much more difficult. What type of rock are you planning on hollowing out?

 

It "could" work....~LOL~

 

Personally, I would stick with explosive force.

[+mrbort]

I hope you're gonna put an ammo can in that hollowed-out rock. You know...to go along with your sig line and all...

 

Where I live we have a lot of pumice that is quite soft and also not brittle and have been planning to hollow out an ammo can sized hole in one. This is almost the ideal rock for it! Then I'm going to hide it in a pile of rocks.

Edited July 29, 2009 by mrbort

[+Casting Crowns]

You'd be surprised what you can accomplish, with much enthusiasm, with a cordless deill with a hammerdrill feature. I use them for work so I made my own hollowed out rock to hide a film can in. It was limestone so it was fairly easy. Then I used a chisel to smooth it out a bit. Worked great. A hole the size of an ammo can??? That's going to take a LOT of patience! Good luck!

[+Team Veverca]

Then I'm going to hide it in a pile of rocks.

Just make sure that you write a hint for it. Something in the lines of "under a rock".

[+mrbort]

Then I'm going to hide it in a pile of rocks.

Just make sure that you write a hint for it. Something in the lines of "under a rock".

 

To make it clear: I don't plan on making it a needle in a haystack hide but it should be fairly challenging especially since I'm planning on putting it in the middle of a cliff giving it a pretty tough terrain rating. There should be plenty of crevices etc to look in before someone checks out the random rock Hoping to do it in such a way that it's not a frustrating find but instead quite rewarding.

 

Hopefully the hollowing out won't be too bad... this type of rock is soft enough to hollow out with a stick. We'll see how it goes

[+Chrysalides]

Hopefully the hollowing out won't be too bad... this type of rock is soft enough to hollow out with a stick. We'll see how it goes

Use a rock hammer. Hide it in a hayfield (I guess you're too far from Maine though). Remember to leave some money there.

[+J-Way]

You'd be surprised what you can accomplish, with much enthusiasm, with a cordless deill with a hammerdrill feature. I use them for work so I made my own hollowed out rock to hide a film can in. It was limestone so it was fairly easy. Then I used a chisel to smooth it out a bit. Worked great. A hole the size of an ammo can??? That's going to take a LOT of patience! Good luck!

This is the best answer in the thread. A hammerdrill with a sharp bit will work with almost any rock, given enough time.

 

Soft sandstone, chalk, soapstone, or pumice? You can hide an ammo can in a few hours.

Hard sandstone, hard limestone, or granite? A film can will take a half hour to a few hours.

Obsidian or chert? Go find another rock.

[+J-Way]

Hopefully the hollowing out won't be too bad... this type of rock is soft enough to hollow out with a stick. We'll see how it goes

Use a rock hammer. Hide it in a hayfield (I guess you're too far from Maine though). Remember to leave some money there.

No, hide it in a rock fence near a hayfield under a big tree. And the rock shouldn't be there.

[+StarBrand]

Hopefully the hollowing out won't be too bad... this type of rock is soft enough to hollow out with a stick. We'll see how it goes

Use a rock hammer. Hide it in a hayfield (I guess you're too far from Maine though). Remember to leave some money there.

No, hide it in a rock fence near a hayfield under a big tree. And the rock shouldn't be there.

Black obsidian as I recall......

[+renruts]

For the stuff I have done I have used diamond impregnated bits as well as a masonry bit.

 

For ammo can sized you may want to check with a lapidary supply house and see if you can acquire a smaller diamond impregnated saw blade.

[+mrbort]

Hopefully the hollowing out won't be too bad... this type of rock is soft enough to hollow out with a stick. We'll see how it goes

Use a rock hammer. Hide it in a hayfield (I guess you're too far from Maine though). Remember to leave some money there.

No, hide it in a rock fence near a hayfield under a big tree. And the rock shouldn't be there.

Black obsidian as I recall......

 

Yeah definitely not drilling into obsidian and we don't really have any hayfields very close to us Especially of the Maine variety! Maybe I'll just go for a different homage and hollow out a bible for the cache container and hide it in a safe.

[aniyn]

I vote for a hammer drill and a chisel. It'll be tough though.

[+RS67Man]

I gave some thought on how I would make a fair sized rock hide for a 1 quart L&L. I would start with a aluminum box with a hinged door and magnetic catch. The door would be on the bottom of the "rock" and the aluminum box would hold the L&L container. The rock would be built up around the aluminum box with mortar/cement, chicken wire, and fiberglass fibers. The finish would be a careful layering of flat enamel paints that have been thinned down to achieve a washed look so the rock looks as natural as possible. The finder would have to roll the rock over to actually find it. It would make a good urban cache in a lower traffic area.

[knowschad]

I hope you're gonna put an ammo can in that hollowed-out rock. You know...to go along with your sig line and all...

 

Where I live we have a lot of pumice that is quite soft and also not brittle and have been planning to hollow out an ammo can sized hole in one. This is almost the ideal rock for it! Then I'm going to hide it in a pile of rocks.

 

You also have alabaster. Years ago, somewhere between Cuba and Albuquerque I found a hill that was full of it. You can whittle that stuff with a pocket knife!

[+Unkle Fester]

 

You also have alabaster. Years ago, somewhere between Cuba and Albuquerque I found a hill that was full of it. You can whittle that stuff with a pocket knife!

Watch your language, this is a family forum.

 

I also heard once that someone made a wrong turn at Albuquerque...

 

Some really good ideas, another thought is a grinding stone for a dremil type tool, for softer rocks would work real well.

[AZcachemeister]

DREMEL

[Chumpo]

It all depends on how big of a rock you're talking about. Your local brick mason might be a big help.

http://img195.imageshack.us/img195/7397/masonrysaw.jpg

Edited July 30, 2009 by Chumpo

[+Chrysalides]

For some reason I can't get the image of a laser in the kilowatt range firing micro bursts to vaporize bits of rock to hollow it out.

 

I tried to look for a video, but the closest I could find is this one :

 

 

Skip to 2:15 for some laser action.

 

It's in WSMR - maybe mrbort can get his hands on one

[+bittsen]

I just remembered something from almost 30 years ago.

A neighbor was adding a rock facade to their house and was using "cultured rock" which was basically formed rock. It is still on the front of their house so it is definately durable but it was a lot softer and lighter than actual rock.

You might check with a masonry supply company to see if they have any cultured rock. You could probably use pretty simple tools to carve out a hole.

I also know, lately, constuction companies have been using a similar product that looks like river rocks.

 

Thanks to the Chumpo for jogging my memory

[knowschad]

DREMEL

 

Dremel

[knowschad]

I just remembered something from almost 30 years ago.

A neighbor was adding a rock facade to their house and was using "cultured rock" which was basically formed rock. It is still on the front of their house so it is definately durable but it was a lot softer and lighter than actual rock.

 

Are you thinking of that stuff that looks like very rough lava rock? If so, that may be what's called "hypertuffa", made from concrete, perlite, vermiculite, and peat moss.

 

Here's an "Instructable" on making fake rocks from the stuff:

[+TheAlabamaRambler]

 

You also have alabaster. Years ago, somewhere between Cuba and Albuquerque I found a hill that was full of it. You can whittle that stuff with a pocket knife!

Watch your language, this is a family forum.

 

I also heard once that someone made a wrong turn at Albuquerque...

 

Some really good ideas, another thought is a grinding stone for a dremil type tool, for softer rocks would work real well.

Back in the '60s, true story, the nearby towns of Siluria and Alabaster considered merging. The plan was abandoned at a joint town council meeting when someone pointed out that no matter what the new town name the folks who lived there would always be known as Silibastards.

 

On topic - old motor oil poured on for bit cooling and a paddle-style drill bit will drill a hole in most rock big enough for a film can.

 

 

OK, an FYI moment: Did you know that if you attach a handle to a drill at the bit end and crank it backwards you can charge cell phones and other batteries with the power cord? Yup, a drill cranked backwards is a generator!

Edited July 30, 2009 by TheAlabamaRambler

[+Chewy_06]

Ive got two inside rock hides:

 

One is a 12" long piece of granite that my old man drilled a hole in with a carbide bit & hammer drill. A bison tube fits in the underside held in with a plug. It's evil, weighs in about 20 pounds & it blends in very well.

 

The other is a "featherlite" rock I picked up at Home Depot for about $7 CAD. The rock is about 18" high, 18" wide & about 12" deep and weighs about 5 pounds. I wasnt able to find out much about them, but I suspect that they're cultured (i'm referring to man-made here). It's extremely light for it's size & is very soft and is coloured that makes it a relatively close match to the large rocks around these parts. I hollowed it out with a 1" spade bit initially & then cleaned up the hole with a chisel. The spade bit did the job, but didnt survive, when it was done, it had a distinct curve, was about 1/4" shorter and the cutting edge was completely rounded off. I've tucked a 500ml lock and lock into the cavity on the bottom.

[TRBof4]

Hollowing a rock, now thats dedication!! I would just opt for the fake variety! Maybe a container shaped like a rock coated in that rock like spray paint....

[+Renegade Knight]

To quote from a movie.

 

geologic changes take "time and pressure" - drip sand and water on it (for long enough) and you'll have a hollow.

 

 

 

(bonus points if you can name the movie....)

 

Shawshank Redemption?

 

 

I did it the "manly way" (only because I didn't have a rotary percussion drill.) I used a 3lb mini-sledgehammer, and a set of 100 year old Star drills. It took me hours and the cache stumped many cachers until I unchecked the "for Premium members" box, and the cache was quickly stolen.

 

I'd go for a softer rock. Pummice you can carve out with your knive. Soapstone would be easy enough to drill out. Chewy looks like he's got a plan b, but given the stealable nature of the finished product I'd go cheap.

[Quentonious]

You can actually buy fake rocks designed for geo catching!!! go to: Shop Groundspeak

[+geodarts]

Dynamite works well. But it also tends to hollow out my house and that of my neighbors so my wife has discouraged me from doing it myself. So fakerock.com does a good job -- the owner told me that one of the pictures they use on their site was sent to them by a cacher.

 

http://www.fakerock.com/whererock.htm

Edited July 30, 2009 by Erickson

[knowschad]

You can actually buy fake rocks designed for geo catching!!! go to: Shop Groundspeak

 

Gag me.

[knowschad]

Dynamite works well. But it also tends to hollow out my house and that of my neighbors so my wife has discouraged me from doing it myself. So fakerock.com does a good job -- the owner told me that one of the pictures they use on their site was sent to them by a cacher.

 

http://www.fakerock.com/whererock.htm

 

Now, THOSE at least look like a challenge, although you can't enlarge the pictures enough to really see what they look like. But most of these fake rocks work only once. They all not only look alike, but most have a semi-famous logo embedded in them that did NOT come from the Jurassic period.

[+snake428]

I have done this with a hammer drill and chisel not to bad

[+Harry Dolphin]

Dynamite. The only way.

[+DragonsWest]

I have a different approach to hollowing a rock.

 

But first...

 

Dark Zen, if you are reading, stop NOW!

 

OK, onward. I've visited the local hardware store and wandered the aisles looking at things for ideas. Great places hardware and garden shops can be. I was looking for one thing and noticed something else I thought could be far more fun for a future cache - plaster. I picked up a large bucket for a mere $5. I figure I'll pay a visit to one of the local beaches for to borrow a pail of sand, then acquire some food colouring from one of the grocers. Last, pick out some nice small plastic bottles from the collection I haven't recycled yet (large-mouthed, stubby) and set to work.

 

1. Dampen the sand in the pail and shape to fit the plastic bottle with a little room to spare.

2. Mix some plaster, using food colourings to get the right shade (try small samplings first!)

3. Pour a bit of the plaster into the mould, place plastic bottle with lid on into it then top off.

4. After plaster has begun to harden, clear around the cap a bit with a dowel or such so the cap can be easily removed. It's essential the cap be flush with the base of the casting for placement and keeping water out.

 

I figure this way I can make my own fake rocks to fit what settings I find.

[+bittsen]

I have a different approach to hollowing a rock.

 

But first...

 

Dark Zen, if you are reading, stop NOW!

 

OK, onward. I've visited the local hardware store and wandered the aisles looking at things for ideas. Great places hardware and garden shops can be. I was looking for one thing and noticed something else I thought could be far more fun for a future cache - plaster. I picked up a large bucket for a mere $5. I figure I'll pay a visit to one of the local beaches for to borrow a pail of sand, then acquire some food colouring from one of the grocers. Last, pick out some nice small plastic bottles from the collection I haven't recycled yet (large-mouthed, stubby) and set to work.

 

1. Dampen the sand in the pail and shape to fit the plastic bottle with a little room to spare.

2. Mix some plaster, using food colourings to get the right shade (try small samplings first!)

3. Pour a bit of the plaster into the mould, place plastic bottle with lid on into it then top off.

4. After plaster has begun to harden, clear around the cap a bit with a dowel or such so the cap can be easily removed. It's essential the cap be flush with the base of the casting for placement and keeping water out.

 

I figure this way I can make my own fake rocks to fit what settings I find.

 

Food coloring won't work for a long term. It's water soluble and will wash out really fast.

A better solution would be Rit dye found in the fabric section of department stores.

[knowschad]

I have a different approach to hollowing a rock.

 

But first...

 

Dark Zen, if you are reading, stop NOW!

 

OK, onward. I've visited the local hardware store and wandered the aisles looking at things for ideas. Great places hardware and garden shops can be. I was looking for one thing and noticed something else I thought could be far more fun for a future cache - plaster. I picked up a large bucket for a mere $5. I figure I'll pay a visit to one of the local beaches for to borrow a pail of sand, then acquire some food colouring from one of the grocers. Last, pick out some nice small plastic bottles from the collection I haven't recycled yet (large-mouthed, stubby) and set to work.

 

1. Dampen the sand in the pail and shape to fit the plastic bottle with a little room to spare.

2. Mix some plaster, using food colourings to get the right shade (try small samplings first!)

3. Pour a bit of the plaster into the mould, place plastic bottle with lid on into it then top off.

4. After plaster has begun to harden, clear around the cap a bit with a dowel or such so the cap can be easily removed. It's essential the cap be flush with the base of the casting for placement and keeping water out.

 

I figure this way I can make my own fake rocks to fit what settings I find.

 

Have you tried this while exposed to real weather? In my midwest experience, plaster will not hold up. I'd advise you to test it before placing it.

[+DragonsWest]

Well, there's always concrete or adobe.

 

I live in California where it only rains a bit of the year. But have had plaster sculptures, you know the kind you make in art classes, hold up rather well in the elements. The Rit dye, which I've used for tie-dye shirts may be the ticket, though weathered is the look I'm going for, so again sample and experiment before placing.

 

I expect an exposed cache where there's considerable ice and snow would require something more durable than plaster, but the idea of creating your own 'rock' seems preferable to changing an existing rock, particularly if it's harder than coal.

Edited July 31, 2009 by DragonsWest

[+bittsen]

Well, there's always concrete or adobe.

 

I live in California where it only rains a bit of the year. But have had plaster sculptures, you know the kind you make in art classes, hold up rather well in the elements. The Rit dye, which I've used for tie-dye shirts may be the ticket, though weathered is the look I'm going for, so again sample and experiment before placing.

 

I expect an exposed cache where there's considerable ice and snow would require something more durable than plaster, but the idea of creating your own 'rock' seems preferable to changing an existing rock, particularly if it's harder than coal.

 

You could always make a rock out of clay and take it to any number of ceramics shops to have it fired. You would have to ask how to get a rock-like finish instead of a shiny one but I know it can be done.

[+DragonsWest]

Well, there's always concrete or adobe.

 

I live in California where it only rains a bit of the year. But have had plaster sculptures, you know the kind you make in art classes, hold up rather well in the elements. The Rit dye, which I've used for tie-dye shirts may be the ticket, though weathered is the look I'm going for, so again sample and experiment before placing.

 

I expect an exposed cache where there's considerable ice and snow would require something more durable than plaster, but the idea of creating your own 'rock' seems preferable to changing an existing rock, particularly if it's harder than coal.

 

You could always make a rock out of clay and take it to any number of ceramics shops to have it fired. You would have to ask how to get a rock-like finish instead of a shiny one but I know it can be done.

 

Then you'd have to glue your container inside whatever cavity.. could do. There's no shortage of glazes which could appear rock-like, in the proper setting.

[+bittsen]

Well, there's always concrete or adobe.

 

I live in California where it only rains a bit of the year. But have had plaster sculptures, you know the kind you make in art classes, hold up rather well in the elements. The Rit dye, which I've used for tie-dye shirts may be the ticket, though weathered is the look I'm going for, so again sample and experiment before placing.

 

I expect an exposed cache where there's considerable ice and snow would require something more durable than plaster, but the idea of creating your own 'rock' seems preferable to changing an existing rock, particularly if it's harder than coal.

 

You could always make a rock out of clay and take it to any number of ceramics shops to have it fired. You would have to ask how to get a rock-like finish instead of a shiny one but I know it can be done.

 

Then you'd have to glue your container inside whatever cavity.. could do. There's no shortage of glazes which could appear rock-like, in the proper setting.

Yup. I honestly think this would be the best method. Could get spendy though, depending on the size of the "rock".

Oh why did I get rid of my kiln???!!!