Bulb Frosting?

[Alex K.]

Hi everyone,

I have seen people with their ROP's bulbs frosted, and it seems to produce a better beam, but when I try it, it has adverse affects. The beam is very weak, and it has a weird shape. Can anyone tell me how to properly frost a bulb?

 

[ma_sha1]

I just use fine sand paper

 

[Alex K.]

Thanks, I gotta go to Home Depot anyway,so I'll pick some up. I was using the only sandpaper I could find, which was from my garage, coarse, and 50 years old.

 

[AlexGT]

This might help

http://www.candlepowerforums.com/vb/showthread.php?t=120285

AlexGT

 

[Lumencraft (Matt)]

+1 for using the Armour etch glass etching. That is what I have always used. You do need to be very careful with it, because it can be dangerous. I have even hear it can cause nerve/bone damage.

With WA1185 Osram 64623, and similar type bulbs it took a bit longer for the bulb to frost for some reason, but the amount of light lost is minimal. I have found with that putting some masking tape over the top 1/3 of the bulb and only frosting the bottom 2/3 is plenty to give a nice soft beam (especially if used in combination with a MOP reflector) without diminishing the out put too much.

 

[Kestrel]

+2 on the Armor-etch. I have mixed feelings about doing what really is damage to high-pressure, high-output bulbs, particularly with sandpaper. I have frosted relatively low-output bulbs (up to the 3754-L) with the Armor-etch but understand that there is the possiblity of heat becoming an issue - a completely frosted bulb should heat up more, creating excess gas pressure in the bulb envelope, which is now not in 100% condition.

And please be careful with that HF etching cream. I wear a lot of PPE when handling that stuff - I've been trained in HF acid handling and have a lot of respect for it. For goodness sake for anyone using this, wear rubber gloves and safety glasses at an absolute minimum and if at all possible, a face shield (protecting the face & neck). The idea of a high-pressure bulb envelope exploding while coated with HF gives me the willies.

Edit: BTW here's another good link on this, with 4 pages of reading:
http://www.candlepowerforums.com/vb/showthread.php?t=99398

 

[Alex K.]

Thanks! Went to Michael's, but they were all out. Thanks for the heat tip, I frosted a 6D bulb and it got REAL hot in the Mag. It also seems that frosted bulbs break or burn out easier.

 

[Al Combs]

And please be careful with that HF etching cream. I wear a lot of PPE when handling that stuff - I've been trained in HF acid handling and have a lot of respect for it. For goodness sake for anyone using this, wear rubber gloves and safety glasses at an absolute minimum and if at all possible, a face shield (protecting the face & neck). The idea of a high-pressure bulb envelope exploding while coated with HF gives me the willies.

Good safety tip. I did some searching on ARMOUR ETCH and ammonium bifluoride. It turns out hydrofluoric acid is a bi-product of this substance being mixed with water. I guess this is one of those times when they say gloves and glasses, they really mean it. Also surprised to learn the goop they spray on your wheels before you go through a car wash contains this compound in many cases.

Maybe a find grade of ≈400-600 wet/dry sandpaper used with water is not so bad after all.

 

[Alex K.]

Thanks about the PPE tip. I'll probably wear an MSA full-face respirator, and thick nitrile gloves.

 

[Kestrel]

BTW I have been impressed with the more uniform hotspot resulting from this technique, the result isn't perfect but well worth it IMO. I generally mask the top half of the bulb and frost the lower half (which is what the reflector is seeing, resulting in the focused hotspot). I figured that there wasn't any point in frosting the top half, and that would also lessen any overheating concerns.

I never posted beamshots of my results (the lights were going to friends and I didn't have the time), if anyone does, it would be nice to see.

 

[Alex K.]

Thanks Everyone for the tips! My Bianchi B-Lite has never had such a smooth beam!