Can HID bulbs be pluged in forwards and backwards?

Just got my 10watt Solarc ballast today from Welch Allyn and was experimenting with it. I noticed that if the bi pin HID bulb were pluged in the socket one direction that it would flicker more than if plugged in the opposite direction. Is there any danger/bennefit in plugging a HID bulb one way or another?

On a side note I noticed when I got the bulb it had yellow slag inside the arc tube & after lighting it up for 10 minutes the yellow crud was vaporized and the arc tube became clear as glass. Perhaps this is what ppl mean when they say you have to break in a HID tube.

Just got my 10watt Solarc ballast today from Welch Allyn and was experimenting with it. I noticed that if the bi pin HID bulb were pluged in the socket one direction that it would flicker more than if plugged in the opposite direction. Is there any danger/bennefit in plugging a HID bulb one way or another?

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All HID's are not the same!! Yes, very much so on DC type arc tubes like the W.A., your bulb life will be greatly diminished if you don't connect it properly. Also W.A cannot be hot restriked. In a DC (current flowing only one direction) arc tube, one electrode is a Cathode the other an Anode. Mostly one electrode, the anode is eroded (looses thoriated tungsten material). In DC powered HID's the anode is a much thicker electrode than the cathode. Electric current passes from the cathode to the anode, producing. much higher rates of electrode erosion on the anode than cathode. Anode (+) and Cathode (-).
Counterintuitive to what we have mostly been taught, electrons actually flow from neg to pos. College Physics.
Automotive type of HID's being an AC rather than a DC system at 300-400 Hz typically, both electrodes share the duty of being cathode and anode this change occurs at the same rate of 300 to 400 times per second. In AC powered HID's both electrodes erode at the same rate. since both share equal time as anode and cathode.

Polarity is critically important in a WA setup. It is a DC type as XeVision stated. BTW, thanks XeVision I learned from that, did not know the anode material and the nature of the erosion. My WA 10W ballast has a tiny embossing to indicate the positive (+) terminals location and there should be a tiny indexing pin on the bulb itself. The asian copycat bulbs do not have this and can easily be plugged in "backwards". Also be super cautious about correct DC input polarity. A reverse polarity or short there will cause serious damage to the ballast in <1 sec, right from the WA Solarc spec sheet. If you dont already have it go to www.walamp.com and look for Solarc datasheets. Hope this helps.

If you purchased your Ballast from WA directly there should be no way you could plug the lamp in backwards as the socket is keyed at least the last 20 I have purchased from them where?

Mac