# Need help on how long to expose a screen



## rockinfunzone (Jul 18, 2009)

I have been using the green speedball stuff from the art store for coating my screen but today I bought some new stuff. It's Murakami Photocure Blue. I need to know the correct exposure time for my set up. The exposure time given for the Murakami stuff says 55 seconds. But that is for a "5Kw metal halide lamp at a distance of 40 inches.". The set up I have been using to expose screens is different, I use a 500w halogen work lamp at a distance of about 12 inches. Are the directions for the Murakami stuff for a real exposure unit or can I really just expose my screen for 55 seconds using a 500W work lamp?


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## out da box (May 1, 2007)

It's probably going to take longer, prob a couple of minutes at the most. The only way you'll know is trial and error or an exposure calculator or step wedge test.


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## rockinfunzone (Jul 18, 2009)

I just exposed the screen for 4 minutes and it came out fantastic! All of my lines came out perfect. I am so glad I got this new stuff instead of the green stuff. I do a lot of fine line work and was a pain to go over and over it to make it as black as i needed it. So I am guessing that this new emulsion will let me keep my energetic, sketch like images intact.

I also have a couple other questions. Why do you coat both sides of the screen? They say its for a "thick stencil". What does that mean? Is it necessary to expose a screen?


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## zea97sk8ter (Dec 8, 2010)

how long do I expose my screen with regular house
hold bulbs


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## PositiveDave (Dec 1, 2008)

http://www.t-shirtforums.com/t-shirt-articles/t106506.html


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## BroJames (Jul 8, 2008)

rockinfunzone said:


> I just exposed the screen for 4 minutes and it came out fantastic! All of my lines came out perfect. I am so glad I got this new stuff instead of the green stuff. I do a lot of fine line work and was a pain to go over and over it to make it as black as i needed it. So I am guessing that this new emulsion will let me keep my energetic, sketch like images intact.
> 
> I also have a couple other questions. Why do you coat both sides of the screen? They say its for a "thick stencil". What does that mean? Is it necessary to expose a screen?



At 12" high, 4 minutes with a 500w halogen worklamp should give a good image although it will also depend on the specific type of emulsion used among others. 7-9 minutes should be more in line with what is referred to in this industry as the proper exposure time with a better durability for your stencil(emulsion). You will actually lose more details though.

A thick stencil is a thick coat of emulsion. It is not necessary but desirable sometimes. For example, if you want a thicker coat of ink on the shirt, an additional coat or two of emulsion (on top of dried emulsion) may be desirable.


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## shirttrader (Dec 27, 2010)

zea97sk8ter said:


> how long do I expose my screen with regular house
> hold bulbs


I haven't tried regular incandescent household bulbs, like what you use throughout the house, but you can get a cheap worklight at Home Depot and use it. Regardless, you'll probably simply need to guess, try different exposure times, and take note of distance and time.

When I first started screen printing I did this and just had to figure out how to mount my lamps (I had some 500w halogen work lights) and I think I had to re-do my screen a few times before I got it exactly right.

That's half the fun, tho...


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## buehrle (Jan 14, 2008)

are you using a home made one or one that is commercially built ? i only use 48-50 seconds with mine and i have never had an issue and have used it for probably 6-7 years this way. i'm not sure of the brand name (can check but it's never let me down).


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## Alan Buffington (Oct 27, 2010)

Are the directions for the Murakami stuff for a real exposure unit or can I really just expose my screen for 55 seconds using a 500W work lamp?[/quote]

I realize this is an older post but here goes since a lot of DIYers use these lamps. Removing the glass will provide more UV light. These lamps contain very little UV light. If it doesn't give you a sunburn its not really a lamp to expose with, just my opinion but you can make them image a screen, the emulsion however will not cross link completely:

Move 500W back to 20-24 inches. otherwise you will overexpose the center and underexpose the edges.

5,000 watt versus 500 watt. That is a ten times difference. So the 5,000 watt is far stronger. A 500 watt lamp may need to expose for 10 minutes or longer to work, or less.

Run a step test to know for sure. Make 11 lines with a magic marker on the print side of a dry coated screen. Tape down really well a detailed positive designed for the mesh you are testing. Block out 9 of the panels with rubylith, amberlith, or a really dark black trash bag. Expose for 2 minutes. Move block out media to next line, expose again for 2 minutes exposing 2 panels. Continue moving blockout media and shooting for 2 minutes. When you have exposed all ten panels you will have exposure times ranging from 20 minutes (first panel) down to 2 minutes on last panel in 2 minute intervals. 

Develop screen. Pick the panel with the best details and NO slime on inside. Wipe with white cloth on inside to verify the panel you have chosen is completely expsoed. More than likely due to the long exposure times needed for a low wattage lamp you will have to chose a panel that has details but is not completely exposed due to undercutting of art by the light. Wash carefully, blow out with air hose and put in sun squeegee side up, or dry horizontally and post expose. Photocure BLU is a good emulsion for these lower wattage lamps.

Al
Murakami Screen USA


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## Alan Buffington (Oct 27, 2010)

ForIsaiah:

Use the sun, I made skimboards one Xmas eve for my sons, took an hour and half to get an image to print a logo on them with a 100 watt bulb and it still was weak.

Send me an email I'll send you a drawing of how to expose with the sun. Best exposure unit ever between 10 and 2 on a sunny day. Try 10-20 seconds depending on mesh using BLU.

Alan Buffington
[email protected]Murakamiscreen.com


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