Short note on magnifying glass fire

[Ascobis]

Greetings,
I owe someone here from the Midlands an autumn magnifying glass fire. I learned something and want to pass it on. I use three and five strand jute gardening twine for my primitive fire starting. I am accustomed to separating the fibers to make a nest for a coal. I found that a tight double figure-8 knot in three strand jute twine collected enough energy from the magnifying glass to form a coal. A single knot cooled too rapidly and charred away. A loose knot did not work. After the coal formed in the larger tight knot, the other end of the bit of jute, untwisted but not frayed fully, caught flame from the coal.

There hasn't been anything new in bushcraft since the pleistocene yet I haven't come across a description of this use of twine in recent reading.

 

[Broch]

Unfortunately, to try out your method, we'd need some sun!!

 

[Paul_B]

Fire by magnifying glass? There's one thing that I wonder about. Is it really possible to make a lens from ice that works?

Sorry about off topic.

 

[Erbswurst]

Should anybody know it, you have to ask somebody from Iceland!

.

 

[nitrambur]

from Mythbusters episode 45

Fire from ice
Myth: You can start a fire by rubbing a block of ice into a shape of a lens and using it to focus a beam of light.

They found some good, high-quality clear ice to use from an industrial ice maker.Kari sculpted a lens shape out of the ice using a knife while Grant made his using a rock. They got smoke from Grant's lens but they couldn't get fire. As the lenses melted, the hot spot dissipated.

Tory and Grant decided to create a lens mold to cast the ice in. Industrial ice makers use pressurized air to agitate the ice to get out the bubbles. Tory and Grant used an electric massager inside a regular kitchen freezer. Their lens came out completely fogged.

Kari decided to make a large sphere of ice. As the sphere melted, it would be able to hold it lens shape longer. Kari got smoke from here sphere. They put up the confirmed sign but they never showed actual ignition.

confirmed

 

[Tony]

Thanks for sharing that Ascobis, I use jute sometimes with flint and steel and combined with other tinder but I've not tried it as you've described, I'll give it a go, there's bound to be some winter sun coming up!

As for the lens from Ice, yeah it's doable, patience in forming it (use the house freezer or it needs to be really cold out) and then some sun, which of course wants to melt your ice Doable though...

 

[Tengu]

Just who invented this?

The Egyptians had lenses, -but we dont know what for. Aristophanes mentions a burning glass in a play...thogh its obvious he has never actually seen one.

 

[Joe tahkahikew]

1st you have to find a glass lens. Then you have to wait till the sun rise. And a little bit up north you may be waiting most of the winter for that.

 

[Bishop]

STREPSIADES: Have you ever seen a beautiful, transparent stone at the druggists', with which you may kindle fire?
SOCRATES: You mean a crystal lens.

Aristophanes in The clouds (420 BC)

The British Museum does have a piece of polished quartz known as the Nimrud Lens that's supposed to date back further. So the encounter could of been possible though it would of been a serious piece of high tech kit for the period.

 

[Paul_B]

Was it pythagoras who supposedly when in service with a king or warlord got them to polish their shields and supposedly used them to set fire to their enemy's sails when the island was under attack? One of a range of technogical advances from the man that includes a great arm supposedly able to pick whole ships up and drop them.

I believe the shields were designed to create a highly polished parabolic curve that with coordination could direct solar energy to a point.

I only mention this because there was a lot of technology in ancient Greece that took until the renaissance to be rediscovered. I don't doubt lens technology was good enough for firestarting back then. But why bother? Like now it would have been little more than an enjoyable test to start a fire that way but if you really needed a fire there's definitely better ways IMHO.

However use of jute thread is a good idea and the knot bit too.

 

[Robson Valley]

A local photographer has been making and using ice lenses for decades.
He has a black styrofoam meat tray as a lens board. He waits for hot sunny weather.
He casts the lenses in the concavity in the bottoms of upside-down beer cans.
Final shapings are done with his bare hands. Kind of drippy but the images are respectable.
Digital camera body with no lens and you're good to go.

I will try the Ascobis experiment when it warms up here a little. Brilliant concept.

 

[Fadcode]

i am sure that lenses have been in use for millenia, It would have been noticed that a raindrop on a leaf would magnify the leaf, and necessity being the mother of inventions, I am sure it would not have taken long to make some sort of magnifying device, and those with eyesight deficiencies would have found some way to enhance and improve their eyesight capability. The one drawback of using a magnifying device to light a fire,as Joe points out, you would need a strong sun, and most travellers, armies etc, would make camp late in the afternoon when the sun would be going down.

 

[Janne]

You need to either be able to shape and polish natural clear uncoloured crystal type quartz, or be able to make perfectly clear glass, and polish it.
I think the last two millenia maybe?
Our own Archeologist Toddy can maybe answer that.

There are easier ways to create fire.

 

[woodspirits]

Reminds me of a post I put up a few years ago, 'Starting a fire with water', it is of course sun dependant

“hiya folks learnt a new skill today, well for me anyway, it was something i came across on the tube a couple of days back.

real easy and it works! you need a small piece of clingfilm, fill it with water and tighten into a ball, just move it around untill you get a fine (hot) focus, just like a magnifying glass and train it onto your tinder.

i had a cramp ball in my bag and i tell you what within a couple of minutes it was going great guns a bit of film weighs nothing, and everything else is to hand, sorted"

#1Aug 9, 2010