What caused this?

[dsgobie]

Well I just pulled my light out of storage. (10W HID) I had it packed up for about 4 months.

I decided to do a burn test to check the battery and what not.

Well I put it in the bath tub, turned it on and checked it about every 30 min to start, and then after 2 hours every 15 min.

I lasted for 2 hours 45 min. Which is good to go.

But when I turned my light off and took the light out of the tub, turned the lights off in the bathroom and was about to leave, I noticed two spots in the tub that were glowing a blue/white color.

The main spot was where the beam was focused. The second spot was from the spill right next to the light head. They were there for about 15 minutes.

Does anyone know what caused this?

Has anyone else had this happen?

 

[Conor]

My best guess would be that the surface has a kind of latent phosphorescence, I guess you would only notice it if part of the surface was charged but the rest wasn't so you could see the contrast.

Its not unheard of for ceramics to have phosporescent properties, so if it was a ceramic bath, or it had a ceramic based coating then it was probably just gradually discharging the energy it absorbed from the light.

Does this make sense?

 

[dsgobie]

Yeah it is a ceramic tub. Well that makes more sense to me than nothing.

Thanks....


Anyone else have a different idea?

 

[Charlie99]

dsgobie once bubbled...
Yeah it is a ceramic tub. Well that makes more sense to me than nothing.

Anyone else have a different idea?

Not a different idea, but just the observation that you can see the same phosphorescent effect by holding your light up against some limestone, then either turning it off or holding it against your chest.

 

[dsgobie]

Now can any light do this or only HID's?

 

[Conor]

Depends....if the tub recieved energy faster than it looses it it will still build up the energy for the effect but at a slower rate, so you would most likely see less for the same period of 'charging'

 

[Greg_Manko]

My guess would be a coating on the tub. Often these coatings have "brighteners" which react with UV to make things "gleem". Could also be residue from cleaning agents?

 

[dsgobie]

Alright, thanks everyone.