Hi!

I'd love to know all about HPS lamp design. I own two HPS wall packs, a 35W and 70W, and I have some spare lamps for both.

I have the original bulb from my 35W wall pack, made in 1996. It's a GE LU35. I have a spare OEM Philips bulb, which has a more narrow arc tube compared to the LU35 and feels cheaper.

The LU35 has silver ends on the arc tube, and the arc tube is quite thick.

I have a nice Sylvania 70W lamp, which feels very robust and doesn't have the silver ends on the arc tube. I also have two coated GE 70W lamps.

I recently bought three NOS GE Lucalox 35W lamps, which appear to be pretty vintage. The box has a description about an external amalgam reservoir, which none of my other lamps have.

What are some of the differences between lamps with an external amalgam reservoir, and those with the amalgam within the arc tube? Are lamps with an external reservoir usually older lamps?

Finally, what are some operating characteristics and expected life between brands of these older lamps and newer lamps, and lamps with an external amalgam reservoir? Do certain lamps warm up with different colors on startup, and do lamps with the external reservoir warm up any slower or faster, or behave any different? It's all interesting to me and how each manufacturer designed their lamps and arc tubes, and what designs became the most reliable. It's also interesting to me how different lamps might be slightly different in the colors they produce while striking and warming up.