# 23W UV Light or 125W fluorescent bulb



## bicho (Nov 19, 2015)

Hello everyone!

I am new here so I hope this is the right place to ask. I am new to screen printing too.

The thing is I have an UV light tubes from an insect killer i had, the specifications are power: 23W / Input: 220V/240V - 50hz/60Hz. I am using Diazo emulsion. 

I also have a fluorescent bulb of 125W and 230V. I know fluorescent does not emit much UV and halogen is better but I do not have halogen bulb at the moment.(It is from a photography light with a reflective cover around it).

The mesh is A3 size.

I do not have much emulsion left and I really need to get this right :/

What time exposure would you recommend me with any of this bulbs??

Thank you!


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## Screen Medics (Feb 23, 2015)

This issue is one of comparing apples and oranges. Halogen light is considered visible light where as UV (Ultra Violet light is not considered visible light. Different emulsions are designed to be cured within specific light spectrum sometimes referred to as temperatures or kelvin. For example 6500 Kelvin is the color temperature of clear sunlight. Ultra Violet is at one end of that spectrum and infrared is at the other spectrum. The kelvin number for Ultra Violet is much lower than Halogen or sunlight.
The important point is that your emulsion must be able to cure at the same kelvin number as your light source (light table) to insure a thorough cure.
To do otherwise is like trying to mix water base and oil base paint and hoping for a good result.
Screen Medics


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## sben763 (May 17, 2009)

Screen Medics said:


> This issue is one of comparing apples and oranges. Halogen light is considered visible light where as UV (Ultra Violet light is not considered visible light. Different emulsions are designed to be cured within specific light spectrum sometimes referred to as temperatures or kelvin. For example 6500 Kelvin is the color temperature of clear sunlight. Ultra Violet is at one end of that spectrum and infrared is at the other spectrum. The kelvin number for Ultra Violet is much lower than Halogen or sunlight.
> The important point is that your emulsion must be able to cure at the same kelvin number as your light source (light table) to insure a thorough cure.
> To do otherwise is like trying to mix water base and oil base paint and hoping for a good result.
> Screen Medics



What huh!!! First uv is measured in nanometers of wavelength, Kelvin is color temp. Although there can be some correlation but not always. UV 0-420nm are invisible. Anything above 400-420nm are visible. UVC 200-275 and UVB 275-325 are used for gemacidal, mold and can be very damaging to the eyes and skin. UVA is 325- 400(425) and the spectrum used to cure emulsion and other UV curing. Diffrent brands of emulsion have diffrent sensitzers so will require diffrent spectrums to cure properly. Most diazo emulsions are dual cure meaning the have a photopolymer base. Depending on the sensitizers used here will determine the final spectrum needed when the diazo is added. Most diazo emulsion perfer the higher end of spectrum of the UVA. Pure photopolymers can run 365-410nm a manufacture will advise their peak spectrum. 

Flourescents actually put out a lot of UV but bulb manufacturers put filters, the white potion to reduce its output. That's why in fluorescent the unfiltered bulbs are use. Daylight bulbs have less filter and can be used but not as good. 


Halogen lights put out little uv and compared to commercial units with 6-8 unfiltered is less then 1/4 of this fluorescent units. The halogen can give better results due to a single point vs a multipoint. 

Kelvin in most UV lights are around 10,000k and drop as you head torward the higher spectrums. A yellow light 600nm will only be 3000 on the Kelvin scale. 


To the op. There will be no way anyone can give you that would be anything but a guess. The bug light will put out some UV as will the other light. Bulb age will also make the output vary.


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