Hi everyone. After a discussion on an earlier thread about a mirror (or mirrrrr as one of our non-American friends says we pronounce the word here) and the possible use of a 5x magnification mirror to aid in starting a fire with a fresnel lens, I did a little experiment today. Here are my (non-scientific) results.

Yes, the 5x magnification will focus the light tighter, going into the lens. However, I found that it was much harder to use 2 hands (one on the fresnel lens, and one holding the mirror), to try and get a fire started. I was using some small dead wood lying around the house. In trying to keep the light tightly focused on a small area, it was much too difficult to try and hold the mirror and the lens and the precise angles needed. Someone more competent than I might be able to do this, I found it too difficult. The good news is that the fresnel lens preformed admirably, and I was able to achieve flames in less than 3 minutes. The wood was dry, and if I had used tinder or perhaps a piece of esbit fuel or the like, I am sure the results would have been much better. This makes me feel much safer knowing the little lens works.

On another note, I picked up a Colibri lighter, model looks exactly like the Windmill SP 1000 http://www.windmill.co.jp/outdoor/sp1.htm , at a garage sale. It was empty, and for $5 I figured why not? So, after making fire with the lens, I did a little experiment with the lighter, and compared it to my Brunton Helios. Again, my results are definitely non-scientific.

Anyway, I filled up the Colibri, and luckily it worked. At least I didn't completely waste my money. I took the lighter outside. The wind was pretty strong today, gusting up to 30 mph and steady at around 10 mph. The Colibri lit, and stayed lit in the constant wind, but went out with every good gust. In addition the cap only opened up 90 degrees, and I feel this would make trying to get up close to something to light it such as tinder on the ground very difficult to light. The Brunton lit, and stayed lit in the steady wind, and the gusts. I then decided to be a little less scientific, and brought the lighters to within about a foot from my mouth, and blew fairly heavily on them to see if they would stay lit. The Brunton stayed lit, and the Colibri went out every time. While this could be a problem with this lighter, or perhaps that it is a used lighter, I am not sure. I did notice that the Colibri's firebox where the ignition coil and flame mix was open, and I can see the coils clearly. The Brunton's firebox, however, is enclosed in what appears to be thin ceramic, and that may be just enough insulation from the wind the lighter needs to say running. Or, perhaps the Colibri didn't like the extra garlic on my breath and just gave up the ghost when I breathed on it. So, I will be sticking with my Brunton, and will keep the Colibri in my Jeep for now as a backup.

Do you think the mirror ALONE would be able to concentrate the sunlight enough to ignite some tinder? It is, after all, a mini parabolic reflector.
The olympic torch was ignited via a parabolic mirror, albeit with more curvature to give a focal point closer to the mirror.

Just a thought..... <img src="images/graemlins/grin.gif" alt="" />

There are solar cigarette lighters around 2x3 inches. There's a holder where you put the cig tip at the focal point and then you point the thing at the sun.

You can make your own solar igniter with a soda/beer can. I used toothpaste and Brasso.

http://www.wmuma.com/tracker/skills/fire/cokeandchocolatebar/index.html

I tried to use the mirror in that manner, but I don't think the magnification is quite strong enough. It may work, and in a moment of desparation, I might sit there long enough to try it, but with the other means of starting a fire at my disposal, using the mirror would be pretty far down the list. I honestly would rather used the good ol' rub 2 sticks together method before trying the mirror.

This was what I was alluding to (I didn't believe it would work on it's own) in the previous thread - at no time did anyone suggest using another lense to help the process !! Maybe my English isn't up(??) to your standards.... Anyway, it's 1am here, and I'll be takin' the DAWGS out in the desert later, so I'll try it for myself just to see....

No, your English is just fine. Better than a lot of people here. Of course, as the Brits would say, English is spoken, American is understood. I just didn't read the thread well enough. So, I have now tried using the mirrrr both ways, and would rather do without having to rely upon it to make fire.

The positive aspect of our field trials is finding out what works, what doesn't and all those variables in between. We all pick our favourite system(s) and rely on their known qualities. It behooves everyone to try everything. We have discussed the scenario of being totally without tools and fabricating them from the environment. It would be very embarressing to dismiss ie magnesium bars only to find ourselves someday with only that very resource and never having practised with one. <img src="images/graemlins/blush.gif" alt="" />

You could always try for sparks off the behooves - that probably WOULD work !!

At one point I did introduce the confusion. I suggested using a flat mirror and a focusing lens to emulate a parabolic dish mirror. This could be used to use a magnifying glass to light the underside of something, but was mainly to show what a dish mirror could do if you did not habve one handy for experimentation. It may have been understood to mean adding the dish mirror plus a magnifying lens.

Frankly I did not think of the fresnel pluss mirror combination. A fresnel lens may not work at all with the light going through it twice because the second pass would involve angles way out of specs towards the edges. It would probably cause great inefficiency or loss of light. Dimming.

The only way I see it working anywhere near well with a fresnel lens is if the light was reflected and the lens placed in the reflected beam, out of the way of shadowing the incoming light. If you are using a dish mirror, the focal length may be too short to have the fresnel lens out of the incoming light and still focusing a considerable amount of the reflected light.