# 500 Watt Halogen Light Exposure Time?



## ajesamann (Apr 8, 2017)

I've tried so many times to expose my screen and I've gotten the same result. The image keeps "blowing out" but just around the design nothing else. Like the edges aren't straight in the design, they look like someone has been picking at them. I am using photopolymer emulsion and I've tried anything from 3-20 minutes and I just cant get it. I let the screens dry for about an hour with a fan on them and I make sure 100% no light is touching them. The screen is 158 mesh. The light is about 13-15 inches away from the screen and i use a piece of glass on top of the transparency. And yes my transparency is dark enough, I've even tried doubling up to make sure. I don't use too much pressure when washing out i just soak it. It's very frustrating and it's wasting my emulsion! Lol any help would be greatly appreciated. I am also curious as to how long you let the screens dry after washing the design out before using. Thanks!


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## splathead (Dec 4, 2005)

There is a formula for distance to light based on image size (not screen size). Generally your light source should be 1.5 times the distance of the diagonal of the art. If your art is 10 inches wide diagonally, your light source should be 15 inches away.

Also, here is an easy way to determine your optimal exposure time wasting just one coating of a screen: http://www.t-shirtforums.com/t-shirt-articles/t106506.html


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## herokid (Jul 22, 2016)

ajesamann said:


> I've tried so many times to expose my screen and I've gotten the same result. The image keeps "blowing out" but just around the design nothing else. Like the edges aren't straight in the design, they look like someone has been picking at them. I am using photopolymer emulsion and I've tried anything from 3-20 minutes and I just cant get it. I let the screens dry for about an hour with a fan on them and I make sure 100% no light is touching them. The screen is 158 mesh. The light is about 13-15 inches away from the screen and i use a piece of glass on top of the transparency. And yes my transparency is dark enough, I've even tried doubling up to make sure. I don't use too much pressure when washing out i just soak it. It's very frustrating and it's wasting my emulsion! Lol any help would be greatly appreciated. I am also curious as to how long you let the screens dry after washing the design out before using. Thanks!


I think everyone goes through it that self learns how to screen print.
What brand emulsion are you using? Also I would think your light is too close, but shoot me a pm and I wouldn't mind helping you get it right.


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## PatWibble (Mar 7, 2014)

Can you post a picture?
You have tried a wide range of exposure times, so under exposure is probably not a factor - at least not in all cases.
That leaves one of two 'most likely' scenarios.

Firstly, the screens might not be as dry as you think they are, and could need longer. If you are using a fan to dry them you need some ventilation in the cabinet or room to control humidity and temperature. Some emulsion doesn't react well to very high temperature when drying.

Secondly you might be experiencing some 'undercutting' during exposure. This can happen around the edges of the design if you do not maintain intimate contact between the film and emulsion. Try putting some foam or a piece of board inside the screen to apply upward pressure to the mesh, keeping it tight on the glass.

A less likely cause is that the emulsion is coming toward the end of its useful life.


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## RedClothing (Nov 14, 2016)

A 500w halogen light (such as a Home Depot work light) is a terrible exposure light. There's almost no UV coming from the bulb. You have a million watt UV bulb over your head every day. It sounds like you have glass and good positives, just walk outside and hold it up to the sun for 30 -60 seconds. Do a few tests and see what happens. UV is what cures/hardens emulsion. Having run a large multi-auto shop for years, you learn to make do when an exposure table quits and you have screens that need made.


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## alrozac (Dec 20, 2012)

Talk to your emulsion supplier and get some test strips. These are reusable and will tell you what is going on with your exposure. Every emulsion burns differently and every unit will give off different amounts of proper light. You just need to test, test, test. Those strips will save you a lot of time and most suppliers will give them to you for free as long as you but their products.


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## Viper Graphics (Mar 28, 2009)

RedClothing said:


> A 500w halogen light (such as a Home Depot work light) is a terrible exposure light. There's almost no UV coming from the bulb. You have a million watt UV bulb over your head every day. It sounds like you have glass and good positives, just walk outside and hold it up to the sun for 30 -60 seconds. Do a few tests and see what happens. UV is what cures/hardens emulsion. Having run a large multi-auto shop for years, you learn to make do when an exposure table quits and you have screens that need made.


I respectfully disagree. I have been using one (from home depot ironically) for over 12 years with no issues. My exposure time is 5 - 6 minutes. Keep in mind to remove the glass from the light housing as that will restrict the UV rays, otherwise they are fine. Your idea of holding up to the sun is...uh...comical. What do you do at night, evening, cloud covered days or when it's raining? Tell the customer you will have to reschedule till the sun comes out?


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## PatWibble (Mar 7, 2014)

Got to agree with Larry. Unless you are burning a lot of screens, Halogen is perfectly usable.

£5.65 for a 500w Halogen and fitting - £250 for a low grade fluorescent unit without vacuum - £4000+ for an LED unit. On the quantity of screens I burn I can afford to wait a few extra minutes.

I started with a 500w Halogen ( like most of us), and graduated to a 6' x6' exposure frame and remote light source when started burning 54" screens for sign printing. I am currently using a 1000w halogen ( and flirting with a UV Led floodlight).

One thing I will say about Halogen lights is watch out what bulb you use. I have noticed recently the units come with 2700k 'warm yellow' bulbs, instead of the 3200k bulbs they used to come with. considering the lower levels of UV that halogen lights produce the difference is massive.
The diagram below shows the output spectrum of the various temperature of bulbs - I put the vertical red line on at about 400nm to highlight the difference.


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## rouge un (May 4, 2019)

PatWibble said:


> One thing I will say about Halogen lights is watch out what bulb you use. I have noticed recently the units come with 2700k 'warm yellow' bulbs, instead of the 3200k bulbs they used to come with. considering the lower levels of UV that halogen lights produce the difference is massive.
> 
> The diagram below shows the output spectrum of the various temperature of bulbs - I put the vertical red line on at about 400nm to highlight the difference.


I've had the same problem as OP using a 500w halogen lamp. Tried several times burning my design onto the screen but they all washed out. My first attempt was for 30 secs at 21" height, then I increased the time to a full minute, then 1.5 mins, and finally 2 mins -- all underexposed. Could the yellow bulb be the culprit for my light exposure failure?

Hope you can point me to the right direction. Thank you!


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## rouge un (May 4, 2019)

PatWibble said:


> One thing I will say about Halogen lights is watch out what bulb you use. I have noticed recently the units come with 2700k 'warm yellow' bulbs, instead of the 3200k bulbs they used to come with. considering the lower levels of UV that halogen lights produce the difference is massive.
> 
> The diagram below shows the output spectrum of the various temperature of bulbs - I put the vertical red line on at about 400nm to highlight the difference.


I am also running into exposure problem with my 500w halogen. Have tried four times burning my design onto the screen, initially at less than a minute, then at 30-second increments on the re-attempts -- all underexposed and washed off after flushing with water. My light source distance was 21".

Could the yellow light be one of the culprits for my negative results? Kindly point me to the right direction; need to know where/what I am doing wrong. Thank you!


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## PatWibble (Mar 7, 2014)

rouge un said:


> I am also running into exposure problem with my 500w halogen. Have tried four times burning my design onto the screen, initially at less than a minute, then at 30-second increments on the re-attempts -- all underexposed and washed off after flushing with water. My light source distance was 21".
> 
> Could the yellow light be one of the culprits for my negative results? Kindly point me to the right direction; need to know where/what I am doing wrong. Thank you!



Like I said in my post, most of the halogen lamps being sold now only come with a 2700/2800k bulb. These emit virtualy no usable UV light.
A few dollars will get you a 3200k bulb that emits more UV.


Your time is very low, and ( depending on the size of your image) your distance is too far. 500w halogens are only really suitable for screens smaller than about 20x24".


Once you have a 3200k bulb, drop down to 15 - 18" and start experimenting with times staring at about 7 mins and upward.


Also make sure you take the glass out of the halogen fitting - this will contain a UV filter and make the lamp next to useless.


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## Chewie12 (Oct 24, 2019)

Thank you for this post. I cam across it today trying to research 500w work lights as exposure devices. 

I recently bought one and have been having long exposure times. 1st screen was at 9 minutes and 21 step strip was around a 12 if I remember correctly and part of my screen would not wash out. 

I started from scratch and increased my time by double and had a worse time getting it to wash out and 21 step was around 10-9. 

Getting ready to do my 3rd screen, but this time I printed another layer on transparency to make more opaque and cross finger increase time to 25 minutes.

I believe I had 3 problems

Transparency not opaque enough
Exposure time not long enough
Bulb is 2900K

Purchased the 3200K bulb tonight but thinking of going back to my 60W UV bulb until new bulbs come in.


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## PatWibble (Mar 7, 2014)

Chewie12 said:


> Thank you for this post. I cam across it today trying to research 500w work lights as exposure devices.
> 
> I recently bought one and have been having long exposure times. 1st screen was at 9 minutes and 21 step strip was around a 12 if I remember correctly and part of my screen would not wash out.
> 
> ...


The 3200k bulb will make a lot of difference.


How far is the light fom the screen?


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## Chewie12 (Oct 24, 2019)

PatWibble said:


> How far is the light fom the screen?


17.5 inches.

It took me a while to find the 3200K bulbs. Either they didn't mention the temp or they were 2900K. They are supposed to arrive tomorrow. Will test it out then.

Last night I exposed my 3rd screen with my old setup of a 60 watt UV bulb, but added a vacuum bag, and printed on the original transparency a second time to make more opaque. 

All this solved my problem and I also used a 1600 PSI pressure washer which made a world of difference.

So glad I found this post.


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## PatWibble (Mar 7, 2014)

have you removed the glas from the halogen lamp - if not most of the uv will be filtered out.


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## Chewie12 (Oct 24, 2019)

PatWibble said:


> have you removed the glas from the halogen lamp - if not most of the uv will be filtered out.


Yes. 

I did use the work light for post hardening though to help dry screen and frame.


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## Chewie12 (Oct 24, 2019)

Got the 3200K bulb in this past week. I was able to try it out on a screen. Drastic difference!!!

Old bulb I exposed for 25 minutes but according to 21 step wedge I should have exposed for 50 minutes.

New bulb I reduced to 15 minutes and 21 step wedge says I should reduce down to 12 minutes and 15 seconds. 

Love the new bulb, but in the middle of building a LED exposure unit so may not use work light much longer.


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## rence12 (Sep 26, 2008)

Ok so I've been using a 500 watt but using Saati Pv 1 on 1 coat , 18 inches , in not sure about the bulb it was just the 500 watt bulb from Home Depot, and have never had any problems , ( I did remove the glass and height 16" and it takes 3 1/2 mins, I've been using this method for about 5 years now , I've burned halftones as well.
Ive thought of switching light sources , after reading how others are burins screens at way less times , but what's 3 1/2 mins , plus it takes so little space. Im happy


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## decca591 (Apr 16, 2013)

I know this is an old(ish) post but would just like to add a note:
I used a screen to find my optimum exposures by using a black card to black out all but the last 2 inches of the screen, expose for 6mins, then pull card back 2 inches, expose for 1 min, repeat across screen and then you have a range of exposure times - wash out and select the best one, then you have something to tweak !!
Hope this helps someone.




Chewie12 said:


> Thank you for this post. I cam across it today trying to research 500w work lights as exposure devices.
> 
> I recently bought one and have been having long exposure times. 1st screen was at 9 minutes and 21 step strip was around a 12 if I remember correctly and part of my screen would not wash out.
> 
> ...


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## dkt (Feb 23, 2008)

Chewie12 said:


> 17.5 inches.
> 
> It took me a while to find the 3200K bulbs.


Chewie12, I am also trying to find the 3200k bulbs, with no luck. Could you please share your source? Thank you!


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## Frankg1718 (Aug 11, 2011)

https://www.amazon.com/dp/B06XJZL97N/ref=cm_sw_r_cp_apa_i_BVCkFbRRHR7PX check this light and the video about on https://youtu.be/bCYr-KNRjBs
https://youtu.be/q8d8aGbttBs
Also check ASPA they have a how to build a exposure unit and light source already being test for it.


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## Chewie12 (Oct 24, 2019)

Frankg1718 said:


> https://www.amazon.com/dp/B06XJZL97N/ref=cm_sw_r_cp_apa_i_BVCkFbRRHR7PX check this light and the video about on https://youtu.be/bCYr-KNRjBs
> https://youtu.be/q8d8aGbttBs
> Also check ASPA they have a how to build a exposure unit and light source already being test for it.


That is awesome!!


I ended up making a DIY exposure unit out a wooden crate I found on craigslist. Half exposure unit and other half a drying cabinet.


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## Camalgo (7 mo ago)

rence12 said:


> Ok so I've been using a 500 watt but using Saati Pv 1 on 1 coat , 18 inches , in not sure about the bulb it was just the 500 watt bulb from Home Depot, and have never had any problems , ( I did remove the glass and height 16" and it takes 3 1/2 mins, I've been using this method for about 5 years now , I've burned halftones as well.
> Ive thought of switching light sources , after reading how others are burins screens at way less times , but what's 3 1/2 mins , plus it takes so little space. Im happy


I am very agree with you. I use he same emulsion, but 15 inches distance of the lamp and 3 minutes. I also use SQB emulsion from SCreen Print DIrect and Orange from Ulano. Have no problems. I need to try with halftones.


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## sbremner (Oct 24, 2007)

If you can, move up to a better light source and a vacuum frame. LED is the way to go, and as I just opined in another thread, get a COB to use as close to a point source as you can. How much time has been lost trying to save some money on equipment? Yes, there are a lot of ways to go cheap, but they end up being costly. Best of luck.

Steve


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