About a month ago, I bought a ten pack of Philips Alto F40 T12 CWS. The package said "these lamps are better for the environment because of the reduced mercury content." Then I got to thinking, isn't that what they do with 34 watt lamps? I have also noticed that old 70's ballasts are just a little bit louder when running 40 watt Philips Altos. What do you all think?

I'm surprised your ballast sounds louder with F40 Altos. As far as I know they're electrically equivalent to any other F40.

Maybe it's just my imagination. I just wanted to make sure I was not unbeknowingly cooking my ballasts. I installed 60 F40 Altos in fixtures that all had 1976 Universal Therm-O-Matic ballasts. Speaking of which, I have said ballast running said lamps above my head right now!

Or the ballasts just get louder over time...

One thing I noticed for sure is that my 1976 Universal gets extremely hot when running Philips Alto F40's. I have never seen any magnetic ballast get so hot running 40 watt lamps. I almost got burned when I checked on it today.

Try that same ballast with a pair of older F40's, does it really stay that much cooler? (I'd be surprised as my understanding was the same as what nicksfans said - that is once the lamps have warmed up, not when there cold/flickery)

I've had 2xF40T12 ballasts that got so hot that you could probably cook dinner on them (infact I discontinued using a couple because they got so hot)

The F34 lamps weren't low mercury like an Alto, there was some difference in the fill gas, and I believe some sorta coating on the glass. I had seen it posted as to exactly what the differences were, but now I don't remember...

The green ends on those lamps are a sign they will poison the cathodes and severely degrade the ballasts.

Just kidding, but I just won't use Altos...have seen many (mostly T8) go mercury-starved (dim, or even pink). I don't like the green ends either. I am partial to GE or Sylvania, or older (full-mercury) Philips lamps. The Altos have the lowest mercury content of all brands, and have thinner glass. Therefore, I would recommend Altos in any location where the lamps are likely to get broken.