Rocks around fires

Submitted: Thursday, Feb 28, 2008 at 07:12
ThreadID: 54998 Views:3448 Replies:16 FollowUps:9
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I am amazed at the many people who place rocks around fires. I have been taught that they are a NO! NO! as many can explode when hot and cause serious injury.

Interested to hear your thoughts and discussion here.

I see it as staking/marking your territory
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Reply By: Ray - Thursday, Feb 28, 2008 at 07:15

Thursday, Feb 28, 2008 at 07:15
I could not agree more. Concrete can do the same
AnswerID: 289758

Reply By: Member - Kiwi Kia - Thursday, Feb 28, 2008 at 07:23

Thursday, Feb 28, 2008 at 07:23
I have never seen it happen myself. Had a few crack but not explode. I would be interested to hear about any 'explosions'.
AnswerID: 289759

Reply By: giffo - Thursday, Feb 28, 2008 at 07:46

Thursday, Feb 28, 2008 at 07:46
I have never seen it happen and I am a Firie.Concrete will loose bits as it gets hot (spalting)Possibly different expansion rates of the material,the rocks might explode if they are the right type and were wet or have water trapped inside,then when that water turns to steam pop ! a can of beans will go bang though !

Cheers
Giffo

AnswerID: 289761

Follow Up By: Camoco - Thursday, Feb 28, 2008 at 10:36

Thursday, Feb 28, 2008 at 10:36
My experience from fire.....

Concrete (the cement dust) explodes like a firecracker (small but volatile) BUT only when directly exposed to very hot flame and through a roughed surface. A smooth surface normally found with concrete does not seem affected due to the chemical coating the water provides through screeding, but a broken piece or slag overburden can 'pop'.
The very hot flame needs to be concentrated like an oxy torch or similar but a 'normal' flame in a camp fire wouldn't be hot enough. Although it could be if another material was there that did get hot enough (like coal) in a concentrated area.
Volcanic rock explodes as stated due to trapped water. This can be quite a large explosion if the pocket is large enough and there is enough water trapped inside. A slowly heated rock would normally allow the water to evaporate naturally before any explosion occurred though, but if you chuck a cold rock in to a well lit fire, then you could have an issue.
Shale is the same due to trapped moisture.

We once had a smelting furnace "go up" quite literally due to water. The furnace had about 2 tonnes of molten steel and the roof was about 15 metres high. Straight through like it wasn't there then back down again.
It was caused by the electrical delivery circuit (water tubes) leaking under the furnace brickwork. The HOT steel made the leak worse then melted out through the crack in the furnace masonry onto a bed of leaked water. I was on top not much before it blew and you could see through the grating the metal leaking out. It was then that we took off and hadn't quite made it down the stairs before she went up. All due to water expanding and the only direction was up and all the steel (molten and otherwise) was lifted very quickly. I have learnt that water is powerful stuff.

One other thing about rocks around fires is they take a lot of time to cool down again causing a potential hazard to the next users and to vegetation that might blow into them. Water used to cool them off just may not be a good idea. Better to not use rocks for a simple camp fire anyway but mounds of dirt if you really need it.

That's my engineering point of view about explosions and fire anyway. My camping opinion is a little different as I use gas mostly.

Cheers Cam
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Reply By: Member - Sam (NSW) - Thursday, Feb 28, 2008 at 07:47

Thursday, Feb 28, 2008 at 07:47
The composition of the rock has a lot to do with it. Some explode more readily than others. Shale is a great one for exploding.

I would have thought though that rocks 'around' a fire are less of an issue compared to rocks 'in' a fire as the heat around the outside isn't anywhere near as great.

But I guess the old saying, better to be safe than sorry comes into play.
AnswerID: 289762

Reply By: AaronBarrel - Thursday, Feb 28, 2008 at 07:50

Thursday, Feb 28, 2008 at 07:50
River rocks that are reasonably flat can and DO explode. We used to do this as kids when we were camping and mum and dad were in bed. It would wake them up and then we would be in all sorts of trouble. It was great fun but very dangerous. All of the river rocks found in the victorian high country definately explode
AnswerID: 289764

Reply By: trolute - Thursday, Feb 28, 2008 at 08:22

Thursday, Feb 28, 2008 at 08:22
Better idea is to dig a short trench, put your fire in that. Less chance of the wind sending sparks into the bush, plus you can cover over the fire before you leave to put it out and to return the area to its original state.

I hate pulling up to a nice camp spot, to only find heaps of old fireplaces everywhere.
AnswerID: 289767

Follow Up By: Member - Franga (QLD) - Thursday, Feb 28, 2008 at 08:31

Thursday, Feb 28, 2008 at 08:31
Be carefull when arriving at a place that you can't see a fireplace, it may have been buried and the earth on top will be hot.
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Follow Up By: Member - John and Val W (ACT) - Thursday, Feb 28, 2008 at 11:06

Thursday, Feb 28, 2008 at 11:06
Each year people (mostly children) are burnt by walking over buried fires. Best to extinguish fire first before covering with dirt or sand. Buried fires can stay very hot for many hours. Parking a vehicle on top of a hidden hot fire might cause a few problems too.

Val.
J and V
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Follow Up By: Scubaroo - Thursday, Feb 28, 2008 at 22:49

Thursday, Feb 28, 2008 at 22:49
As the other posters said.

If you're going to fill in a firepit, make sure it's been fully extinguished with water - literally saturated - and cold to the touch.

Burying a fire doesn't put it out.
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Reply By: 93 Navara - Thursday, Feb 28, 2008 at 08:26

Thursday, Feb 28, 2008 at 08:26
Most rocks are fine. River rocks can explode but I've only ever seen it happen to ones we've thrown in the fire as kids. At worst on the dge they'll crack.
AnswerID: 289768

Reply By: Member - Davoe (Yalgoo) - Thursday, Feb 28, 2008 at 10:19

Thursday, Feb 28, 2008 at 10:19
dunno bout exploding but thats how aboriginals make Gnamma holes they light a fire on granite and it would crack and laminate allowing bit by bit a hole n the granite.
I heard this and forgot about it but had a fire on a granite rock once and sure enugh I could hear crack crack crack andi could have chipd away 1/2 cm or so afterwards. - would have taken them a while
AnswerID: 289780

Reply By: Member - Barnesy - Thursday, Feb 28, 2008 at 14:40

Thursday, Feb 28, 2008 at 14:40
I've been making campfires for years and only had one problem using one type of rock. They spat out small bits of stone. Apart from that nothing. Except from the odd crack.

Using rocks protects the fire from wind, they heat up helping to keep feet warm and makes the coals last longer. Rocks make a better fire.

Barnesy
AnswerID: 289813

Reply By: Moose - Thursday, Feb 28, 2008 at 15:21

Thursday, Feb 28, 2008 at 15:21
If the rocks are already around a fireplace then presumably they would have exploded previously (assuming they were going to) so I never worry about it.
For new spots I usually dig a hole (assuming the ground allows it) and use the excavated dirt to create a wind break. Then when finished I douse the fire, spread the coals around, and refill the hole with the dirt.
AnswerID: 289820

Reply By: Member - Alan H (Narangba QLD - Thursday, Feb 28, 2008 at 16:24

Thursday, Feb 28, 2008 at 16:24
I have seen rocks around the edge of a fire explode on several occassions. On one particular occassion it exploded and rock fragments were subdued but the force threw a large amount of hot coals around the area and damaged canvas.

It seems to be some urban myth that to light a fire you need a ring of rocks. It is a danger that can be avoided so why take the risk?
AnswerID: 289833

Reply By: Member - Bucky (VIC) - Thursday, Feb 28, 2008 at 16:39

Thursday, Feb 28, 2008 at 16:39
We like to dig a hole, to contain the fire, and to give it some definition.
Sometimes we can't, but the places we frequent, the hole just gets bigger every time we are there.

When we leave, there are only footprints, and wheel marks left, and the pit is doused.


Cheers
Bucky

AnswerID: 289837

Reply By: Member - Min (NSW) - Thursday, Feb 28, 2008 at 18:04

Thursday, Feb 28, 2008 at 18:04
Back in the 60's when we were young and very inexperienced we built a fire back from the beach. In no time rocks were exploding. My skirt, made of the very new fangled Terylene, melted where a piece of rock landed and and I still have a scar on my arm where another flake of landed.
John 'n' Min

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Reply By: Wayne (NSW) - Thursday, Feb 28, 2008 at 19:13

Thursday, Feb 28, 2008 at 19:13
didiaust,

Rocks and rubbish in fire places is a pet hate of mine.

Rocks only add to amount of stuff that has to be removed to dig a pit. The dirt, with out the rocks, can then be replaced to extinguish the fire.

Two things about some one getting burnt feet while stepping on a old fire place.
1. It is an fire place don't step on it
2. You should aways wear shoes or boots while out camping.

Also billies balanced in a fire place waiting to tip all over the fire or worst still over someones legs.

I like to dig a pit for the fire and place the billy on "fire irons" that I have. Chains allow the height of the billy above the fire to be adjusted and very little chance of boiling water being split. Boiling billies can also be removed from the fire safely.

Image Could Not Be Found

Wayne
AnswerID: 289862

Follow Up By: equinox - Thursday, Feb 28, 2008 at 21:14

Thursday, Feb 28, 2008 at 21:14
Hi Wayne,

Nice set-up.

Tell me? You have 3 aerials. I'm guessing UHF and HF. What is the third one for??

Cheers

Alan
Looking for adventure.
In whatever comes our way.

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Follow Up By: Wayne (NSW) - Thursday, Feb 28, 2008 at 22:13

Thursday, Feb 28, 2008 at 22:13
Alan,

At the time the photo was taken I had the two UHF aerials on the bull bar.

This photo shows how the set up is now with one UHF on the rear wheel carrier and one on the bull bar.

I have two UHF radios, one I use to talk to the convey and the other is on scan all the time to listen for other vehicles using UHF.

There is also another GPS aerial on the roof of the vehicle just in front of the wind deflector.

Image Could Not Be Found

Wayne

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Follow Up By: equinox - Thursday, Feb 28, 2008 at 22:35

Thursday, Feb 28, 2008 at 22:35
Ahh it all makes sense now.

Once again nice set-up

Regards
Looking for adventure.
In whatever comes our way.

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Follow Up By: Hairy (NT) - Friday, Feb 29, 2008 at 01:08

Friday, Feb 29, 2008 at 01:08
Sounds like a bit of a Furphy?Image Could Not Be Found
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Follow Up By: Wayne (NSW) - Friday, Feb 29, 2008 at 01:14

Friday, Feb 29, 2008 at 01:14
Hairy,

I was wondering how long it would take before someone worked out where it came from.

Wayne
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Reply By: GerryP - Thursday, Feb 28, 2008 at 22:31

Thursday, Feb 28, 2008 at 22:31
River rocks definitely are a candidate for exploding. Have seen it a couple of times and the explosion can be quite dramatic. Saw one explode, fly up into the air, then one of the larger pieces exploded again about 4 feet above the ground. Definitely would not do it again!
Gerry
AnswerID: 289913

Reply By: Member - Vic S (VIC) - Monday, Mar 24, 2008 at 02:16

Monday, Mar 24, 2008 at 02:16
Just had three nights at Woods Point Victoria camped next to to Goulburn River ,round river rocks and flat shale rocks do explode and melt holes in tents six meters away !!! Also gas lighters that are empty make a big bang when burnt with other rubbish by mistake.
Vic
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