You are correct, Role. You have to be careful putting things on them as well as how you clean them. I use a microfiber cloth to clean mine. The other thing is they are a dust magnet. I was using lens brush on mine to try and keep the dust off the mirror and still ended up having to do some dust spotting in Photoshop. Because most dust is light colored (I think mine was albino dust on the day I was shooting with the mirror) it shows up really well reflecting light against the black. Mine is a little bigger than that (I think 16x1
that I found on the internet on a site that sold mirrors for making Kaleidoscopes and things like that that use front surface mirrors. For those that google for them, they also go by the name first surface as well as front surface.
Copier glass is also low iron so it doesn't have the green tinge that regular float or plate glass has. I've been saving some so that someday I can make another small tank to hold water to place things in to shoot. I used regular plate glass to make my first tank that I filled up with tonic water and then put flowers and fruit in for the bubble effect. It should be better with the low iron glass.
Thanks for the comment on my picture, Role.
Mike