is there a way to tell the age of a Radium halide bulb?
 

I recently went back to my halide setup. I have two radium bulbs, one purchased in 2013 and used over a year and another purchased in March of 2015 and used a few months. The problem is I forgot to mark them when I took the new one out and now I have no clue which is which. Is there any way to tell? The only difference I see is one is marked v9 after the made in germany, and the other is marked z8. I assumed the z8 one was the newer one, but I honestly have no idea. The only other difference is the v9 one the bulb part inside is hazy on the ends, where on the z8 one it's totally clear.

Just buy new if your in doubt.

Do you have access to a PAR meter? The one purchased in 2013 and used over a year should be putting out much less.

Without a par meter i dont think you can tell just by looking at them

Do the bulbs yellow/warm as time goes on?

Without access to a PAR/Spectral meter what if you fired one bulb and let it warm up than snapped a photo with all the house lights off, then swapped them and did the same. While you would not be able to tell by just looking at them running perhaps you would with side by side pictures on a computer screen.

Just an idea, no idea if it would work.

Maybe, but it would be subjective. Radium has an English website. Maybe you can email them the codes on lamps and ask which is the newer lamp? Just an idea as well. You could explain your situation.

Yea no par meter. I'll just have to buy a new one and keep these as backups. Teach me to not mark things

The bulb arc actually turns clear as it ages. When they're brand new the bulb arc will be black from the phosphor coating

Hmmm that could be it then. I remember when I got my last builb noticing the haze on the inside. One of them still has quite a bit, the other is totally clear. I guess the hazy one must be the newer one. Thanks.