Hello again,
I'm in the process of building my 1000w metal halide exposure unit and recently read that the ballasts for the bulbs are very delicate and cannot be turned on and off as easily as a normal exposure unit. Does anyone have any ideas to prevent this from happening?
Thanks
My bulbs last for years. You cannot instant start the ballast, you have to wait a few minutes for it to power up. You have to build some kind of shutter system or I use a wood plate to act as a shutter to "turn" the light off and on.
My bulbs last for years. You cannot instant start the ballast, you have to wait a few minutes for it to power up. You have to build some kind of shutter system or I use a wood plate to act as a shutter to "turn" the light off and on.
I recently created a 500 watt halogen exposure unit. I have a metal halide light but never thought of putting it in the exposure unit. Seems to be way too bright of a light and the start up factor is annoying and time consuming.
Is that an ideal exposure unit? more light the better?
I'll look into trying it out. I have trouble with light passing through my transparencies with the with the 500watt and I have to double up on the transparencies. Metal halide would destroy those.
What do you recommend with light passing through designs on transparencies? I'm using a generic laser printer. Still researching for a good large format printer.
i don't remember where i read it but, halogen is on the other end of the light spectrum than a halide bulb; it's closer to infrared. uv light cures emulsion.
if you use a laser, get some toner-aide to spray on after you print the film, it makes a huge difference. also don't use clear transparencies, use vellum or laser film, they will have much better opacity
The spectrum has nothing to do with exposing screens, it's all about the UV. Halogens (although I use one, while building a MH unit) put out comparatively little UV, they will work fine, it just takes quite a bit longer to expose (18mins vs <1min with MH).
Not sure if it's going to work out that well however, as a MH takes somewhere in the area of 10mins to fully warm up, although I'd still be cutting my exposure time almost in half.
The spectrum has nothing to do with exposing screens, it's all about the UV.
... UV is defined by its place on the spectrum. It's light; invisible to the human eye, visible to some other species. The entire goal of exposing a screen through non-natural means (like a lamp) is to make sure you use something that includes the part of the spectrum you need - i.e. UV (Ultraviolet).
... UV is defined by its place on the spectrum. It's light; invisible to the human eye, visible to some other species. The entire goal of exposing a screen through non-natural means (like a lamp) is to make sure you use something that includes the part of the spectrum you need - i.e. UV (Ultraviolet).
My mistake, I thought Macmiller was talking about color temperature of the lights.
Wavelengths of UV light:
UVA - 315-400nm
UVB - 280-315nm
UVC - 100-280nm
Below are a few illustrations of average wavelength distributions by each type of light:
Halogen:
Average Fluorescent:
Metal Halide:
The spike at 365nm on the metal halide illustrates why they work so well for exposure units. However, I would like to know how the color temperature affects this, I couldnt find much googling that.
However, I would like to know how the color temperature affects this, I couldnt find much googling that.
expanding on your research and Solmu
UV light sits on shorter wavelength than visible light and cooler color temperatures seem to have shorter wavelength so cooler the color temperature better the results in the exposure.
halogen bulb produces good results for me
results: my designs burn into screen the way I made it. Will try halide and see the difference.
I would like to know how the color temperature affects this, I couldnt find much googling that.
Color temperature is a measure of visible light. An incandescent lamp filament glows when electricity runs through it. This is one reason there is so little UV and so much Infra Red energy emitted. Metal halide lamps do have filaments, but the inert gasses in the lamp are tuned (doped), to emit the output desired by the manufacturer. Fluorescent lamps don't have a filament, but rely on the coating inside the lamp to emit UV energy.
The color of the glowing filament is compared to an industry standard metal and measured with the fancy scientific Kelvin scale we learned in school.
The 'color' of a candle flame might be 1800 Kelvin and has no comparison to the actual Celsius/Fahrenheit/Kelvin temperature of the flame that would burn your hand.
UV-A energy is invisible, so color temperature is of no value.
__________________
How are you measuring? former Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
Metal Halide exposure unit 
