Magnifier for fire question

[jw2n]

When evaluating a magnifier for starting fires, what should be the priority? Is it the overall size, or is it magnification? I have not played with these for over 40 years.

 

[Spark]

Fresnels typically work the best, but the problem with magnifiers is that they require sunny days, something not typically in supply when you need a fire.

 

[s_f]

The diameter of the magnifier should be more important.

In theory every light that shines through the lense is collected in the focus of the lense. So the more light you get, the higher the intensity.

There could be the issue that you get a blurring of the focus - which means the light is not focused at a distance of... e.g. 25 cm but 25 +/- 0.1 cm (lets call these 2x 0.1cm the error of the focus length which is 25 cm).
I assume this could be caused by a low quality of the lense and the absolute error of the focus length should be greater for lenses with a greater focus length (those have less magnification).

IIRC this does not apply to very thick lenses - there you should get a blurring just because they're too thick.

So usual magnifications/focus lengths (i guess they're between 10 and 50 cm) and a great diameter (10 cm should be nice) should be best.


I already used some glasses of someone with hyperopia for lighting a piece of paper in summer at midday.

In case you're interested: the optical power of glasses is measured in dioptre (at least in europe ) - which is the inverse of the focus length of the lenses of the glasses in meters.
So glasses with -5 dioptre have a focus length of -0.2 meters. Makes sense - these are dispersing lenses.
Glasses with + 2 diotre have a focus length of 0.5 meters - sun light is focused at a distance of 50 cm behind the lense and that's where you should be looking for the focus.

s_f

//edit & PS.: In the book "Lord of the flies" (we had to read it in school a few yrs ago) they make a fire with the glasses of someone with myopia... kinda funny

@ spark: i think that stuff makes fun. Sure, there are much easier and more independent ways to light a fire and i wont get a magnifier and have it on me but it could be interesting for people that already have a pair of glasses for hyperopia on them anyways.

 

[jw2n]

I have a plastic fresnel which I have not used yet. I have nearly every other option of creating fire covered and learned. I am looking at learning another method. While looking at binos, zeiss magnifiers came up which is why I am asking.

 

[newknife]

I've started serveral fires with this:

http://goinggear.com/index.php?main_page=product_info&cPath=5&products_id=170

fits in your wallet.

 

[Rick Marchand]

I use a Hudson Bay Tobacco Box in my kits. It has a lens in the lid. Great on those sunny days. I like to get a coal in punkwood then blow it to flame. It is possible to get to flames with a lens, but conditions need to be just right. My thoughts are that tinder is more important than size or magnification.

Rick

 

[storl]

I've started serveral fires with this:

http://goinggear.com/index.php?main_page=product_info&cPath=5&products_id=170

fits in your wallet.

Seriously? If so, that's pretty cool. I have one that I got from the supplier that is about 8 x 10 and I can make concrete smoke with it. It lights ANY decent tinder into a full flame in a matter of seconds with good sunlight.

 

[PayetteRucker]

I find a flashlight reflector and cigarette to be much easier. A flashlight reflector will produce a very thin, intense focusing point that can be placed right at the tip of a cigarette. On the intense high desert sunny days we have around here, it takes negligible time before the cigarette is lit.Should give you about a 10 minute ember to produce a flame from your tinder...

 

[Spark]

Seriously? If so, that's pretty cool. I have one that I got from the supplier that is about 8 x 10 and I can make concrete smoke with it. It lights ANY decent tinder into a full flame in a matter of seconds with good sunlight.

Hells yes, I picked up one of those at Wal-Mart... I cracked it, but if you are hauling something to keep one from breaking it's like having a laser for starting fires with.

 

[Guyon]

I've started serveral fires with this:

http://goinggear.com/index.php?main_page=product_info&cPath=5&products_id=170

fits in your wallet.

I've got a couple of those I bought at Ben's Backwoods. This thread makes me want to go out and try them. It's certainly hot enough out.

 

[DOC-CANADA]

Doc

 

[newknife]

Hells yes, I picked up one of those at Wal-Mart... I cracked it, but if you are hauling something to keep one from breaking it's like having a laser for starting fires with.

The one I got from goinggear are flexible plastic. They fit in your wallet and won't crack or break.

 

[Spark]

The 8x10's are a bit larger and thicker, check them out and you'll see what I mean. The wallet sized ones are fantastic to have though, but like I said, the 8x10 is like a laser.

 

[newknife]

The 8x10's are a bit larger and thicker, check them out and you'll see what I mean. The wallet sized ones are fantastic to have though, but like I said, the 8x10 is like a laser.

Do you have a link for one of these? I looking for them on goinggear but couldn't find them.

 

[Angus McGunnigl]

I'll second the 8 x 10 being a laser. My 8 year old was starting fires within minutes.

 

[newknife]

I'll second the 8 x 10 being a laser. My 8 year old was starting fires within minutes.

Can you post a pic or a link to the 8x10 magnifier?

 

[MrPan]

Can you post a pic or a link to the 8x10 magnifier?

Go to your local OFFICE MAX and buy one. They carry the 8.25'' x 11'' for around $8.

 

[storl]

Do you have a link for one of these? I looking for them on goinggear but couldn't find them.

I don't have them on the site. I do have a bunch of them though, so I should probably add them...

EDIT: OK, here they are.

 

[Angus McGunnigl]

I got my 8 x 10 at Walgreens a couple years ago.

 

[kozak6]

I once purchased an 8x10 at a dollar store.

My hand lens, a junky GemOro 10x 21mm Hastings triplet, is entirely useless for firestarting. If I remember correctly, I couldn't even feel a warm spot if I focus it on my hand. If I remember, I'll see if it does any better with the summer sun.