How to test exposure time... in the sun

Here you can discuss issues related to exposing screens for screen printing. This includes determining the exposure, light sources and washing out the stencil in the washout booth. Emulsion issues may also be addressed here.

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nexal
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How to test exposure time... in the sun

Postby nexal » Fri Apr 21, 2017 2:27 am

Hello and thank you so much for all the great knowledge you have put out there.
We've been printing on fabric for a year or so using the stencil and dabbing technique, which is cool for simple designs (can actually make gradients once you get the hang of it) but now we want to graduate to screen printing. Thing is we live in a very sunny place and we actually love the idea of exposing our emulsion in the sun (there is the issue that we can't afford to buy professional equipment at this time, but hey, we're romantics). The company making the emulsion (jacquard) states that sun exposure is possible, so that's covered but the question is: how to test for proper exposure time (ET)? The manufacturer states 10 to 45 sec ET. Assuming sunrise at 7:00 and sunset at 20:00, we've tried several exposures between 12:00 and 13:30 for 40 seconds.
We are not getting consistent results. Would you have any suggestion(s) for an experimental setup to test the emulsion more consistently?

Thank you in advance for your time.


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Catspit Productions
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Re: How to test exposure time... in the sun

Postby Catspit Productions » Tue Apr 25, 2017 1:38 pm

You're very welcome. I'm glad I can help out from afar through my video and online work.

Using the sun is inconsistent and it takes some getting used to in order to be able to wing it as needed. I would pick the same time of day and only use a 30 minute window perhaps where you do a series of tests using the step wedge method as in photography. You should be able to look that up online but basically you use an opaque piece of paper to block off the emulsion coated screen and use increments of time for each exposure while pulling the paper back each time slightly. You can pull it back in as many increments as needed to determine the exposure time. I'll probably make a video about it soon.

It probably sounds more complicated than it actually is. But the sun is the real issue here since its UV intensity can vary day to day and hour to hour.
Jonathan Monaco
Catspit Productions, LLC
Learn how to screen print tee shirts!

http://catspitscreenprintsupply.com/
http://www.youtube.com/user/CatspitProductions

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nexal
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Joined: Fri Apr 21, 2017 1:48 am

Re: How to test exposure time... in the sun

Postby nexal » Thu Apr 27, 2017 2:48 am

That is brilliant!
Will look it up but your explanation makes sense as is.
Thank you so much!

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Catspit Productions
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Re: How to test exposure time... in the sun

Postby Catspit Productions » Thu Apr 27, 2017 12:21 pm

You're very welcome. Good luck!
Jonathan Monaco
Catspit Productions, LLC
Learn how to screen print tee shirts!

http://catspitscreenprintsupply.com/
http://www.youtube.com/user/CatspitProductions


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