# Exposing on a cloudy day



## tdh646 (Jan 28, 2009)

I've had great success exposing my screens using the sun. I expose them for about 70-80 seconds with no problem on sunny afternoons. However, the past couple of weeks have been terribly cloudy here in the SF bay area and I need to expose some screens urgently. Is it possible to expose on a cloudy day and if so for how long? I don't have any exposure unit except a halogen light that I have used but it took way too long (about 30 min and even then the face side wasn't fully cured).

Thanks again,

T


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## TshirtGuru (Jul 9, 2008)

tdh646 said:


> I've had great success exposing my screens using the sun. I expose them for about 70-80 seconds with no problem on sunny afternoons. However, the past couple of weeks have been terribly cloudy here in the SF bay area and I need to expose some screens urgently. Is it possible to expose on a cloudy day and if so for how long? I don't have any exposure unit except a halogen light that I have used but it took way too long (about 30 min and even then the face side wasn't fully cured).
> 
> Thanks again,
> 
> T


That's difficult to answer. I would try double time and see where you are at with a test screen. And go from there.


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## pukingdeserthobo (Jun 3, 2008)

like Henry said the only way to fine out is to test


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## out da box (May 1, 2007)

Been there, done that. It wasn't until I figured out how to build a decent exposure unit that I had success screen printing. It's all in the screens. There are a lot of posts about building exposure units. I'm sure you could build one that will work, rain snow sleet or shine. And probably for less than 150 bucks. Good luck.


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## out da box (May 1, 2007)

Sometimes you can see a lighter shade in the emulsion where the image is burned in. If you can see the image, it's probably pretty well exposed.


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## InkedApparel (Mar 18, 2009)

I built an exposure unit for under 100 bucks....but it is made out of old pallets that I got for free...the only thing I bought was the light fixtures and bulbs.....now I need a thicker piece of glass...the one I use is bending from the weight I use to hold the film tight to the screen....I use a 500 watt halogen for now....30 minute burn time are killing me.... 5 minutes to burn a screen with the unit below.

[media]http://www.t-shirtforums.com/members/inkedapparel-albums-forum-pictures-picture919-homemade-exposure-unit.jpg[/media]

Inked


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## Zardiw (Aug 13, 2017)

As long as your stencil is dark enough, I'd go for a few minutes....maybe 4 or 5 depending on how cloudy it is.....also depends on what type of emulsion....mixed kind or ready to go kind.

Full bright sun for me is about 70 seconds using Textil PV which supposedly exposes a lot faster than the mixed kind. Now this is for a fairly thick stencil, so it takes more time to penetrate. A thin stencil would probably expose in 20 - 30 seconds or so.

But here's the deal. It doesn't hurt to over expose....as long as your stencil is dark enough so it can take the time needed to penetrate through the stencil.

But here's another consideration......in full bright sun, you have a 'point' source for the UV rays....which means they will hit your screen and penetrate in a straight line.

When it's cloudy, you got UV rays coming from all angles......I THINK.....lol....seems like the rays would bounce around the clouds b4 hitting the earth anyway.....maybe they burn straight through though.

And UV rays coming from all directions will penetrate somewhat UNDER your stencil from the sides.....so there is that.

Test it out is probably the best solution.....or gamble......lol.....

You could make several test areas on one screen...and expose for different times by covering them with some tin foil........

z


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## dwhite53 (Apr 28, 2017)

You can buy a 250 or 500 watt work light at Home Depot or Lowes for $15 or less. I paid less than $10 for my 250 watt. REMEMBER TO TAKE THE UV filtering lens OFF.

The money spent will probably save you a LOT of time and aggravation down the road.

Expose when time is convenient. Know your parameters are repeatable.

All the Best,
D. White


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## Ricks2524 (Mar 20, 2019)

Will the outside temperature have any effect on exposing with sunlight other than freezing temps


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