I have some rectangular blank CD-Rs the same size as business cards. When used as CD-Rs they hold about 120MB. They're mirror-shiny (with a prism rainbow across it) and have a small spindle hole in the center. They came in a plastic slipcover.

Can anyone see any drawback to using these as signal mirrors, ones that can also hold a data backup? Would the spindle hole be good enough as a sight hole? What obvious problem makes them a poor choice for including in an EDC kit that I'm missing?

Please read Doug's article of signalling devices and the data on CDs. In a word, buy a dedicated signal mirror.

A signal mirror with targetting aid is very cheap and much more adequate for this emergency task. If you're really stranded and need to signal, for example, an aircraft passing over your head, you will be happy you have something more adequate than a small CD-ROM.

My 2 cents.

A guy I used to know compared a several kinds of reflective things over distance with the help of a friend, and a CD was among them. He said the CD looked okay fairly close, but didn't do much over distance.

He was a tiny bit annoyed to find that the item that made the brightest flash was his wife's pink-plastic-framed hand mirror from the bathroom, that she used to make sure the back of her hair looked right.

Sue

That "safety-pink" plastic-framed hand mirror may have been made of real glass - thus the high quality reflection.

I've purchased several of the plastic signal mirrors, but after seeing the high reflective quality of a good glass mirror I've switched to the small glass signal mirrors sold at countycom.com. It is heavier than its plastic counterpart, but it really reflects nicely.

Short answer; CD's break.

A real signal mirror is cheap and vey effective.

tro

I see no problem with your idea.

Homeless people also hang regular CD's around their camps to keep bugs away.

My EDC is a large metal signal mirror. It is best to have the right tool for the job!

OK, that's kind of what I thought. The idea came to me when I saw a CD I left on the front seat of my SUV (bad disk, was going to throw it away later, not worried about heat death!) and it flashed in the sun. Thanks for the replies, especially Susan -- it's the clearest of many good reasons not to.

Although the bus-card CD-Rs would probably make a good way to back
up important documents to be kept in a PSK. Just not as a good signal mirror. -Gary

EDIT: I followed Chris's advice and read DR's page on signal mirrors. And wouldn't you know, right there in the equivalent of bold type: why a CD-R isn't a great idea. My apologies, I read the forums everyday, and got caught forgetting there is more to this website than just the forums.

Ditto!

The Ritter PSP mirror is good but most of the plastic mirrors do not work anywhere near as good as a glass mirror. You can't beat a real glass signal mirror with the bright spot, sighting system.

Just shine them on the side of your building at work and they speak for themselves. Plastic is just a blur and glass projects a bright spot.

The Boy Scout Store has them for about seven dollars.