How do I operate any mercury vapor bulb and/or a metal halide without a ballast?

I have seen some YouTube videos of some folks operating mercury vapor, metal halide and high pressure sodium bulbs on a incandescent bulb to limit current, but they never explain how.

I can't find anything about how this is done. What's the secret? For clarity: secret = what wattage incandescent bulb with for what hid wattage?

• Just buy a self-ballasted mercury-argon vapor lamp. They include the tungsten, all nicely built in and designed for each other.
– jonk
Mar 5, 2020 at 7:34
• thank you for your time to answer my question but my goal is to operate any hid bulb, i should of been more specific, my bad.
– jwr
Mar 6, 2020 at 0:39
• No problem. Then you need to know this: tungsten increases its resistance by a factor of 10 when going from room temp to about $3500\:\text{K}$. Conversely, mercury-vapor lamps have a glow-phase and a glow-to-arc phase transition which has a very high "negative resistance" response. Tungsten (except for its long time constant) is a good fit for these applications. But it has to be designed, too. You can't just slap a random incandescent together with a random mercury-argon bulb.
– jonk
Mar 6, 2020 at 1:54