Removing Outer Glass Envelope From Metal Halide Bulbs?

Jimster · Aug 4, 2019

Before everyone gets their panties tied into a knot, I know that the glass keeps things safe and the issues about the UV and high voltage. I'm over 60 and don't need mothered! My question is more out of curiousity, but does anyone have any experience with the metal halide bulbs that have their outer glass shell removed or broken? I know the glass filters out most of the UV light, but I'm curious what frequencies and how powerful the blocked UV is. Is it mostly UVC, A, B? I used to mess around with the old school sun lamps that used the quartz arc tubes, and have seen it burn the shit out of plants in short order, but I was curious just how much of the differing UV bands are being affected.
Any armchair scientists out there?

MIMedGrower · Aug 4, 2019

Most metal halide bulbs have no outer jacket. Thats why they are meant for enclosed fixtures. Hps and conversion bulbs have outer jackets.

Its a dangerous risk but i think many growers have been using single jacketed mh bulbs in open fixtures for best results for years. But its not the uv we are being protected from but explosion.

Jimster · Aug 5, 2019

Every bulb that I have used for the last 35 years has had the arc tube inside a glass enclosure. There are also special bulbs that are designed to prevent this from happening, but if you look up any 1000w MH bulb, I only see the ones that look like ordinary light bulbs with the glass bulb. CMH might be different, but I'm just talking about MS-1000 bulbs. HPS is a little different, but constructed the same for the most part.
1000 Watt - BT37 - Metal Halide - Grow Light
4200K - 120,000 Lumens - ANSI M47 - Plantmax PX-MS1000

$23.28 ea.

as opposed to the protected bulbs:

Lighting can be confusing! Expert Help - Call Now
1-972-954-4302

SYLVANIA 64714 - 1000 Watt - BT56 - Metal Halide
Protected Arc Tube - 4200K - ANSI M47/O - Mogul Base (EX39) - Base Up Burn - MP1000/BU-ONLY

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OldSSSCGuy · Aug 5, 2019

Sorry, but ALL metal HID bulbs come in a glass enclosure. Its required by the CPSC and other agencies for safety reasons. I'm sure MIMedgrower misunderstood the question...

Its for UV filtering, and to stop burn potential, and protect from the 'dripping' of halide from the element. You can see often those balls of halide rolling around inside the glass - and they (I think) usually vaporize again when the bulb gets up to temp. I trust EYE Lighting and I think they have a full tech explanation on their site.

But don't do it buddy... ain't prudent at this juncture... heh...

Jimster · Aug 5, 2019

OldSSSCGuy said:
Sorry, but ALL metal HID bulbs come in a glass enclosure. Its required by the CPSC and other agencies for safety reasons. I'm sure MIMedgrower misunderstood the question...

Its for UV filtering, and to stop burn potential, and protect from the 'dripping' of halide from the element. You can see often those balls of halide rolling around inside the glass - and they (I think) usually vaporize again when the bulb gets up to temp. I trust EYE Lighting and I think they have a full tech explanation on their site.

But don't do it buddy... ain't prudent at this juncture... heh...

I understand the risks. I know how halide and HPS work and the theory behind them, and I know the glass is on there for UV filtering. You can see when the different compounds inside the arc tube get vaporized, often with a red or yellow flash, depending on the mix inside the tube. Often, the metal balls are mercury, while the halide materials are the yellowish deposits inside the arc tube. There are 3 varieties of UV, as I'm sure that you know. Different formulas of glass allow different frequencies of UV to pass, or not pass. UVC is filtered almost totally by the glass, UVB mostly filtered, and UVA isn't usually filtered too much, like car windows. Your side and back window allow a ton of UVA, but your windshield stops most of it. I'm curious as to the amount of the different UV permeability depending on the glass being removed or left on, as well as the composition of the glass. More Iron = less UV transmissions, but it varies between UV-A, B, and C.
The old arc tubes inside the old school sun lamps are what brings this all to mind. I'm just wondering what, if any, fill gas was used or if it was just a straight arc.

MIMedGrower · Aug 5, 2019

There are single and double jacketed bulbs. That is what determines if they can be used in an open fixture. Even though growers use mh in open reflectors most warn enclosed fixture only.

Hps use double jackets and thats one of the reasons mh gives more uv.

Jimster · Aug 5, 2019

MIMedGrower said:
There are single and double jacketed bulbs. That is what determines if they can be used in an open fixture. Even though growers use mh in open reflectors most warn enclosed fixture only.

Hps use double jackets and thats one of the reasons mh gives more uv.

If you look closely, the "protected" ones actually have a small metal cage built around the arc tube, as the outer glass shell wouldn't provide much protection in the event that the arc tube went tits up. You are correct in the double jacketed ones are meant for open fixtures, but one jacket is glass (outer shell) and the other is metal. The arc tube itself is quartz, which lets all the UV get thru. I always assumed that the enclosed light reflector units were mainly for keeping things cool and easy to tie into the vent system
But, then again, I'm a daredevil! I even use a bulb that says horiz Burn Only, in a vertical position! Wild, I'm telling you! I once found a damaged leaf on one of my plants... and did nothing about it!!
Totally wild, I tell you!! :cool::cool::cool:

MIMedGrower · Aug 5, 2019

Jimster said:
If you look closely, the "protected" ones actually have a small metal cage built around the arc tube, as the outer glass shell wouldn't provide much protection in the event that the arc tube went tits up. You are correct in the double jacketed ones are meant for open fixtures, but one jacket is glass (outer shell) and the other is metal. The arc tube itself is quartz, which lets all the UV get thru. I always assumed that the enclosed light reflector units were mainly for keeping things cool and easy to tie into the vent system
But, then again, I'm a daredevil! I even use a bulb that says horiz Burn Only, in a vertical position! Wild, I'm telling you! I once found a damaged leaf on one of my plants... and did nothing about it!!
Totally wild, I tell you!! :cool::cool::cool:

Thank you for straightening me out on that.

cemchris · Aug 5, 2019

Yeah Explosions. HPS are under vacuum so when they pop they just kind of implode into pieces. MH are under pressure so when they pop they throw glass everywhere including the quartz tube in the middle. Why you see the shielding on that. To keep if from shattering the glass on a hood. Double jacketed ones are made to use in non glass enclosed hoods/ bare. Basically you can't pass commercial inspections with non double jacketed MH in a open hood. Sometimes depending on the inspector and if you have a suppression system they might not even pass you with MH and open hoods period. For example with the Nanolux Maxpar DE MH's

cemchris · Aug 5, 2019

Basically It's just a safety thing

Jimster · Aug 6, 2019

cemchris said:
Yeah Explosions. HPS are under vacuum so when they pop they just kind of implode into pieces.

The HPS arc tubes actually have a lot of pressure in them when they are burning. The arc tube structurally is much stronger than the ones in the MH bulbs, but the area os pretty small compared to MH. There are also the Low Pressure Sodium bulbs that are much yellower in color and, like you said, have low pressure in them, sort of like a neon bulb. The HPS need to heat up high enough to vaporize the sodium inside, which raises the pressure much more than MH. Don't get me wrong... MH also generate pressure, but it isn't quite as high as a HPS. I think the difference is the way the sodium reacts VS the halide, which doesn't have such a pressure increase. For whatever reason, the sodium lamps require a much more confined are space and higher pressures to work properly... the tubes inside are pretty tough!

cemchris · Aug 6, 2019

Jimster said:
The HPS arc tubes actually have a lot of pressure in them when they are burning. The arc tube structurally is much stronger than the ones in the MH bulbs, but the area os pretty small compared to MH. There are also the Low Pressure Sodium bulbs that are much yellower in color and, like you said, have low pressure in them, sort of like a neon bulb. The HPS need to heat up high enough to vaporize the sodium inside, which raises the pressure much more than MH. Don't get me wrong... MH also generate pressure, but it isn't quite as high as a HPS. I think the difference is the way the sodium reacts VS the halide, which doesn't have such a pressure increase. For whatever reason, the sodium lamps require a much more confined are space and higher pressures to work properly... the tubes inside are pretty tough!

It might be the quartz in the MH vs the HPS. I'm not 100% sure why cause I'm with you on the logic but I do know fire marshal threatened to shut us down for the open hood MH's and didn't give 2 shits about the HPS's. He came in saying "I need to see all of your MH fixtures if you have any." So with that I'm going to say maybe its a fire issue vs a safety issue. He never explained it even tho I asked. Just said code.

cemchris · Aug 6, 2019

Meant to add we had those Maxpars in 2 rooms and he was ok with those. The other place he shit a brick about the 30+ open hood SE MH's in the veg room.

Jimster · Aug 6, 2019

cemchris said:
Meant to add we had those Maxpars in 2 rooms and he was ok with those. The other place he shit a brick about the 30+ open hood SE MH's in the veg room.

The industry is still young... sooner than later there will be new laws and ordinances that make it a pain in the ass to do anything. Mandatory eye protection, respirator masks, someone will sue the industry after eating 5 lbs of buds and having a bad trip... it only takes 1 lawyer to screw it up for everyone. Never underestimate authority, it creeps into every crook and cranny in society, like a beer fart.

Removing Outer Glass Envelope From Metal Halide Bulbs?

Removing Outer Glass Envelope From Metal Halide Bulbs?

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