# Setting up a light box for exposing



## ramesh.vinay (Mar 5, 2010)

Hi,

I am planning to make my own light box for exposing screen. I use SR exposing emulsion. My instructor said it will take 3 minutes if i use 120 watt bulb. Can i use cfl bulbs. I am from india, bangalore. Thanks..


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## RichardGreaves (Nov 7, 2006)

Your instructor promised a 3 minute exposure with a 120 watt compact fluorescent lamp, but lamps used for visible light are very poor emitters of invisible UV-A energy. UV light can be harmful to eyesight & home furnishings. 

Lets get him to explain his outrageous suggestion.

A CFL lamp is "compact" and it will be hard to get even distribution of UV energy.

If you want to expose with fluorescent lamps shop for* BL*, "blacklight" lamps.

Also popular for the hobbyist are 500 watt quartz halogen work lights with the UV safety glass removed. They are very hot and only generate about 3% UV energy, but they are a single point light source.


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## BroJames (Jul 8, 2008)

I think his instructor advised 3 minutes using a 120w incandescent bulb(a guess) and the TS is asking if he can used CFLs. 

I read somewhere that a 25w or so CFL, hung 12-18" above the film positive, can be used for photographic emulsion but it takes 45 minutes or so. I have tried using a 55w CFL (about 20" high) but a 10 minute exposure resulted in an almost complete wash-out.

A Hong Kong Company claimed that the 23w CFLs that *they sell* can expose emulsions in 15-20 minutes.








source: http://www.wai-hang.com.hk/e_screen_printing.html


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## Violent_J (Mar 8, 2010)

500 watt halogen should take seconds to minutes


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## BroJames (Jul 8, 2008)

Violent_J said:


> 500 watt halogen should take seconds to minutes


A 500w halogen set 12" above the screen should expose the same in about 3 minutes. At 18 inches about 4 minutes. At 24 inches, which is what I used to do, 5 minutes or thereabouts. Give or take about 30 seconds


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## scottyjr (Sep 12, 2009)

BroJames said:


> A 500w halogen set 12" above the screen should expose the same in about 3 minutes. At 18 inches about 4 minutes. At 24 inches, which is what I used to do, 5 minutes or thereabouts. Give or take about 30 seconds


I agree. These times are in the range of what to expect from a 500w halogen. - Scotty


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