Using a magnifying glass to start a fire

[Arizroughrider]

My wife carries a small glass one in her first aid kit and it has been awhile since I have practiced this method. It had rained the day before and the tinder was damp, too. It was about 1550 in the afternoon. The small tinder bundle is made from Shaggy Juniper.

 

[ged]

Hehe, Arizona, that's easy. Come and try it in England!

 

[maddave]

Good effort there. I too carry a small magnifyer and it works... However I have tried the same technique with a Freznel lens and was dissapointed with the result. Doesn't seem to focus the beam quite as precisely as glass.

 

[andyc54]

just been given one (bcb make i think ?) off my step son whos a squadie as a present when he came back from his nco carder in cyprus its a great present but its hard work in england and never actauly tried a proper fire just burnt paper and wood will have to try it if we get some sunshine this summer

 

[maddave]

just been given one (bcb make i think ?) off my step son whos a squadie as a present when he came back from his nco carder in cyprus its a great present but its hard work in england and never actauly tried a proper fire just burnt paper and wood will have to try it if we get some sunshine this summer

Try with a bit of amadou, cattail fluff or charcloth. I had the best results with these. Paper can be a pain and so can birch bark for some reason?

 

[JohnC]

Ive tried it with lenses and found if I darken the tinder in any way it works better, gets glowing and can be added to a tinder bundle

 

[Shewie]

Not tried this since I was a kid but I ordered a couple of jewellers loupes off the web the other night to have another crack.

 

[stovie]

Did it quite successfully with a reversed binocular the other day...just a little more tricky keeping the beam focussed...

 

[ged]

... I have tried the same technique with a Freznel lens and was dissapointed with the result. Doesn't seem to focus the beam quite as precisely as glass.

Most Fresnel lenses are floppy plastic and optically poor. At the best of times the focus isn't so good as even a modest quality glass lens, but when they flex, the focus goes all over the place. If you can mount the lens on something that will keep it flat that will help a lot. The nice thing about them is that you can get very big ones quite cheaply, and the large size can more than make up for the slightly dodgy focus. I have one about 8" x 10" (cost a couple of pounds) and in strong sunlight, even in England, it will light a crumpled cardboard box in five seconds flat.

It's worth preparing the area where you will focus the beam. Something like some dark tinder nestling in the inside corner of a cut-open cardboard box is good. The sides of the box heat up and so reflect heat back to the tinder in the hot spot that you're making. That can improve the energy density no end. Even if the tinder is damp you can dry it out very quickly using the lens, and then it will light easily. Dark surfaces absorb the sunlight better than light ones, so if you have for example paper which has been printed with black ink that's usually better than white paper. The tinder material should ideally be fibrous to allow oxygen to get at it better when it starts to burn.

 

[MartinK9]

Arizroughrider

Nice one.

Dave and Neil had sucess at Northwood in April with a Fresnel Lens:

Wallet sized and a great emergency item.