Light source to screen

why would do you feel that the metal halide can't be that close? it's only 400W and I'm pretty sure that a worklight/halogen light gives off more heat than a metal halide. I might be wrong about that, but I heard that the worklight setup(which I also have) gives off a lot of heat per watt compared to other setups.

I would probably set it further away anyway as you might want to do larger prints, but it will also increase your exposure time.
I am going to be building a Metal Halide unit at some point soon. I have a few free 320 bulbs I got from someone, but after the price of the ballast I could get a 1000W bulb and Ballast for only $100 more so far from doing research.

That do make sense bout what u said on the first half. But I can't no exact distance that people would recogmend or even play with. I'm new to the game. I jumped in The game head first and seems like I'm just doing everything twice. Just like making this exposure unit. If I knew I would of start out with a metal halide. But I guess everything is a learning process that cost$$$$$$$

yeah no matter how much you read up or watch on youtube you still have to do it yourself in the end..
It does seem that the professional made metal halides have the ligth source very far away from the screen/glass, but I think that's because those lights are 2,000W and up and can also be used for larger screens..
I haven't researched this too much, but I if I do or if i find anything I will get back to you. There should be a few DIY threads for metal halide exposure units on here already if you can find them.

Appreciate the help I'm gonna do more search too

Try here:

[media]http://www.youtube.com/watch?v=x9NrndxeCJ4[/media]

thatboiDEE said:

I jumped in The game head first and seems like I'm just doing everything twice... But I guess everything is a learning process that cost$$$$$$$

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I suggest stopping and jumping alllllll the way back to the beginning and either purchasing a comprehensive DVD instruction, go to a class series, a book like "How to print t-shirts for fun and profit" or watch a Youtube series like Roger Jennings. Make sure you have a clear understanding of all the elements of screen printing and how they go together. You'll save money and time and frustration in the long run.

TYGERON said:

I suggest stopping and jumping alllllll the way back to the beginning and either purchasing a comprehensive DVD instruction, go to a class series, a book like "How to print t-shirts for fun and profit" or watch a Youtube series like Roger Jennings. Make sure you have a clear understanding of all the elements of screen printing and how they go together. You'll save money and time and frustration in the long run.

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Awwww Dr. but running full speed into a wall has it's merits too.
Seriously, it does get easier if you can see someone do it right before you start.

cyclesurgeon said:

Awwww Dr. but running full speed into a wall has it's merits too.

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Haa-haaa!!!

And jumping into the deep end of the pool before swim class starts.

"Oh, Lord! Is there a Doctor in the house???"

Nice to see your thieving hands are still attached

I figured what the formula was about. It's 1.5x the diagonal length of screen. So it's 27x1.5=40.5. 40.5 inches don't sound right.

What doesn't sound right about it?

The Sun is 93 million miles away (on average) and can cure emulsion in 20-45 seconds because it's pure UV.

Mh isn't pure UV so it would have to be considerably closer (like 40"...LOL). But the part of the light spectrum that exposes emulsion is more intense with Mh than say a comparable Halogen.

I have a 1000W Halogen (and 2 high actinic tubes) and it's about 36".

Atlas 5-way vac-u-lite, right? (had to guess)

So if I have a 20x24 screen with a 12" square of emulsion, and a 34x34 screen with a 12" square of emulsion I'll need a different light distance?

If you have the bulb next to the screen - the centre gets cooked before the edges are even turning. If you have it too far away, everything cooks at the same rate but very slowly.
The amount of light received is inversely proportional to the square of the distance.
Basically you need a compromise that gets an even burn in a reasonable time. About 1.5x your diagonal is a good rule of thumb but feel free to experiment and see what works for you.

I'm a give 30 inches a shot. I did a diagonal measurement from where the screen coats n that what I got. Gonna be another learning process just like everything else.

thatboiDEE said:

I figured what the formula was about. It's 1.5x the diagonal length of screen. So it's 27x1.5=40.5. 40.5 inches don't sound right.

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I think its 1.5 the diagonal length of the largest image you plan to expose. At that distance the UV at the edges of the image is about 10-15% less(I think) than on the center. You can afford to expose larger spot images though.

TYGERON said:

What doesn't sound right about it?

The Sun is 93 million miles away (on average) and can cure emulsion in 20-45 seconds because it's pure UV.

Mh isn't pure UV so it would have to be considerably closer (like 40"...LOL). But the part of the light spectrum that exposes emulsion is more intense with Mh than say a comparable Halogen.

I have a 1000W Halogen (and 2 high actinic tubes) and it's about 36".

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2 UV fluorescent lamps? Where exactly to you position them?

ScreenFoo said:

Atlas 5-way vac-u-lite, right? (had to guess)

So if I have a 20x24 screen with a 12" square of emulsion, and a 34x34 screen with a 12" square of emulsion I'll need a different light distance?

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Fooooo!!

Good guess. Exactly right. (You been peekin'? )

And you'd probably use a bigger piece of film too right?

I'm so confused. Then again, that may have nothing to do with this topic...

BroJames said:

2 UV fluorescent lamps? Where exactly to you position them?

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The main bulb is in the middle at the bottom and the two tubes are on either side closer to the top. They're a "bump" exposure but they expose very well alone.

cyclesurgeon said:

I'm so confused. Then again, that may have nothing to do with this topic...

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You been huffin' spraytack again???