How do I hollow out a rock?

[+DragonsWest]

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???!!!

 

This is why I'm starting out with plaster. Keep the cost down if possible.

[+Chrysalides]

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

Because you needed room for the indoor 25' waterfall, remember?

 

Clay's a great idea, thanks!

[+bittsen]

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

Because you needed room for the indoor 25' waterfall, remember?

 

Clay's a great idea, thanks!

 

WHAT?!

 

How did you know about the waterfall??

[+Chrysalides]

How did you know about the waterfall??

Well, there's that incident with Homeland Security, crop circles, Hugh Hefner and 27 wild geese. I can't say more because of the gag order.

[+JABs]

I have a piece of Granite which I hollowed out using a dimond rock coreing bit.

 

It now has a film containor in it and sit's out in the middle of an open paddock like area.

 

But it helps when part of your work is a hardware store and you can borrow these items.

[+Gitchee-Gummee]

Best idea yet..............................

 

Take a load of beach sand, shape it into what you want, compact it tightly, place in under 20 ton/sq in pressure, let it sit for a short period of time (50,000 yrs or so) and.................... BINGO. There you have it, EXACTLY what you were looking for.

[+Chrysalides]

Best idea yet..............................

 

Take a load of beach sand, shape it into what you want, compact it tightly, place in under 20 ton/sq in pressure, let it sit for a short period of time (50,000 yrs or so) and.................... BINGO. There you have it, EXACTLY what you were looking for.

Some might ask, what if you need to use it today?

 

Why, you use the time machine, of course!

[+bittsen]

Best idea yet..............................

 

Take a load of beach sand, shape it into what you want, compact it tightly, place in under 20 ton/sq in pressure, let it sit for a short period of time (50,000 yrs or so) and.................... BINGO. There you have it, EXACTLY what you were looking for.

Some might ask, what if you need to use it today?

 

Why, you use the time machine, of course!

 

Or...

 

Find an active volcano.....

[+warpling]

I recently made a hole in a brick using just a drill press and a large bit.

[+DragonsWest]

Making a test rock in one of those vending maching bubbles with a bison tube tucked in.

 

I added Rit black liquid dye to the mix for the shade of grey. Rather looks like concrete. Perhaps darker next go.

 

Casting in sand would probably work much better as this plaster mix expanded slightly out the top of the mould. Should dry faster and be easier to extract from mould, too. This may have expanded and require breaking the plastic to remove it.

 

No idea how it will hold up in weather. Guess I'll have to plant it somewhere, after a little carving to make it a bit more uneven in appearnance.

 

Still, it's fun to try new things.

 

[+swizzle]

If you take all the time and effort of carving out a real rock the size of an ammo can then you really need to protect it. I would definately make it premium members only, hide it at least 3 miles back in the woods and make the rock a big one. Say 80lbs after its carved out. Personally I would go with a make your own out of concrete. A buddy of mine did just that with a peanut butter jar in it. The rock is definately showing signs of deteriation though and it was place in 2005 or 6. Can anyone recommend a type of concrete that will hold up better? I was also wondering if rebar or hardware mesh should be used to help strengthen the "rock" I don't think you'd need to much cover if you can get moss to grow on it before you place it. But then again the constant moist enviroment may have been his rocks undoing. Swizzle

[+swizzle]

Making a test rock in one of those vending maching bubbles with a bison tube tucked in.

 

I added Rit black liquid dye to the mix for the shade of grey. Rather looks like concrete. Perhaps darker next go.

 

Casting in sand would probably work much better as this plaster mix expanded slightly out the top of the mould. Should dry faster and be easier to extract from mould, too. This may have expanded and require breaking the plastic to remove it.

 

No idea how it will hold up in weather. Guess I'll have to plant it somewhere, after a little carving to make it a bit more uneven in appearnance.

 

Still, it's fun to try new things.

 

 

I'd say a bit too glossy. That'll stick out like a sore thumb. Maybe try greasing the inside of the bubble and then getting fine sand to stick to the grease. (vaseline, grease, butter, oil, slice of raw bacon?) Anything that'll hold the sand onto the bubble. I'd try a different container for the shape. I started off using those bubbles to try to make fake ant hills. Still working on that one. Just some ideas for you to try. Swizzle

[knowschad]

hide it at least 3 miles back in the woods and make the rock a big one. Say 80lbs after its carved out.

 

Oh, my aching back!!

[+bflentje]

Seriously how.

 

I've done it a few times. The hardness of the rock does matter in how easy/difficult it is. I have a Hilte hammerdrill that goes through stone like a hot knife through butter. Of course having the correct equipment really helps.

[+bflentje]

hide it at least 3 miles back in the woods and make the rock a big one. Say 80lbs after its carved out.

 

Oh, my aching back!!

 

I recently pulled the 120 pound faux tombstone I used for a cache container out of the woods. Talk about aching backs. Now that's one where I really could have used the help of the sheriff's department.

[knowschad]

hide it at least 3 miles back in the woods and make the rock a big one. Say 80lbs after its carved out.

 

Oh, my aching back!!

 

I recently pulled the 120 pound faux tombstone I used for a cache container out of the woods. Talk about aching backs. Now that's one where I really could have used the help of the sheriff's department.

 

You should have let me know! I would have been glad to report it to the sheriff for you!

[+DragonsWest]

Update on Plaster.

 

It's rubbish. OK, next I'll see what I can do with cement mix. Fortunately sand will not be a problem.

[+swizzle]

Update on Plaster.

 

It's rubbish. OK, next I'll see what I can do with cement mix. Fortunately sand will not be a problem.

 

I love experiments like this. I'm wondering if you used a slightly larger container and glued in some cloth bunching it up a bit here and there and then added your cement. Once its hardened pop the whole thing out and you'll probably have to burn the cloth off. I'm thnking it might create the creases that you see in other types of rock. A bit less obvious then a perfect form. Just an idea. Swizzle

[+DragonsWest]

Update on Plaster.

 

It's rubbish. OK, next I'll see what I can do with cement mix. Fortunately sand will not be a problem.

 

I love experiments like this. I'm wondering if you used a slightly larger container and glued in some cloth bunching it up a bit here and there and then added your cement. Once its hardened pop the whole thing out and you'll probably have to burn the cloth off. I'm thnking it might create the creases that you see in other types of rock. A bit less obvious then a perfect form. Just an idea. Swizzle

 

OK, the plaster object has indeed turned very hard, but it chips easily. Looks unsuitable.

 

However (!) I found a bag of concrete, 10 lbs for 2$ at the hardware store. Being the experimenter I am I bought one. I also filched a pail of sand from the beach.

 

Creating moulds in wet sand is a breeze. Add just enough water so you can shape the sand, make sure the insert container fits well inside then mix up some concrete, right in the kitchen sink (good thing I don't have a wife yet, this could have been a fatal error), pour some into the bottom of the mould, insert container, then fill in around it and sculpt with an old knife. Make sure edges of bottle I'm using are free of the concrete so fingers can twist it out. It's set now, but I'll probably wait until morning to pull it out and have a look at the finished product.

 

Make 'em Ugly

 

This will be such a homely cache container, not to mention heavy and rough, I don't see it being stolen, though who knows what logic exists in the alleged minds of cache thieves? This is intended to replace a missing cache at a state beach down the coast. Pictures to follow.

[+Steve&GeoCarolyn]

 

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

 

Very cool! Have you tried doing this? Or something similar?

 

Carolyn

[+DragonsWest]

Last night's experiment worked pretty well, though i had a rather lumpy form. This morning I mixed a couple small batches of concrete and pulled out my 1" trowel and went to work on it, adding a little here and there to give it a more defined look and drifted completely away from ordinary rockness to an old style mile stone. Interesting. Throw some plaster on this and let it sit in the sun for a few days and I may have somethng which would have an aged look to it as the elements work on it, to my advantage. Neat.

 

Looked through the instructible (what a load of annoying ads!) and think there's some potential there, but harkening back to when I was a wee lad, we made some papier mache pinatas. I think that technique would work better for a hollow form.

 

Mix wheat paste (usually flour, sugar and water) and cut newspaper into strips.

Inflate a balloon to desired size and knot end.

Dip paper in wheat paste (make sure it's well coated with the stuff) and apply around the balloon.

Let dry overnight.

Insert pin to pop balloon, paint as desired.

 

I'd diverge from this by cutting away what I don't want of the paper ball and adding chicken wire or some mesh bag I get potatoes and oranges in. Apply layers of concrete and other compounds as described in the instructible and I have a hollow rock which the container isn't an integral part of. Could probably take this a bit further and make a skull, just in time for Halloween.