AFAIK, anything higher than 6000k is painted/coated.
Thanks..
i found some good info about HID. here
http://www.intellexual.net/hid.html
Quoted:
Color in light is caused by the absence of other primary colors; therefore a blue bulb is a bulb that lacks red and green hues. This also means that a white light is the presence of all primary colors of light. White light is more intense than any single color by itself. Why do you think those novelty black lights are so dim compared to regular incandescent bulbs? In fact a 5800K bulb is 800 lumens dimmer than a 4100K bulb made by the same manufacturer. It is also useful to know that 6000K is the highest marketed color temperature produced by the top lighting manufacturers in the world. Most bulbs marketed at 6000K are actually producing color slightly lower than 6000K. The reason 6000K is the plateau isn't because they physically can't make an 8000K bulb. It is because anything above 6000K is not effective as a lighting instrument. So don't believe those ebay auctions boasting "Revolutionary 12000K HID bulbs from Germany". That is just BS marketing gimmick at work.