# Exposure time



## MANNYMARISCAL (Dec 5, 2006)

I am using 500 watts halogen lamp to expose my screens. The screens are 19x22 110 mesh. What’s a good time to expose my images?


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## Fluid (Jun 20, 2005)

your going to need to do some tests. Its best to get yourself an exposure calculator. Your screen print supply vendor should have them.

You also need to specify the type of emulsion your using as they all have varying exposure times.


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## MANNYMARISCAL (Dec 5, 2006)

I am using ULANO QTX


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## RichardGreaves (Nov 7, 2006)

MANNYMARISCAL said:


> I am using 500 watts halogen lamp to expose my screens. The screens are 19x22 110 mesh. What’s a good time to expose my images?


There is no magic time for exposure. You have lots of variables and you have to make an actual test with your conditions. No one can tell you the correct exposure.

*Variables*

*Output of UV*
This lamp is not made for screen making. Hundreds of companies make J style 500w lamps. They are not designed to output UV light, but some do. You are using Ulano QTX which is sensitized at the factory with SBQ. Diazo, Dual-Cure and SBQ are all sensitive to different spectrums of light.

*Age of the lamp*
As the lamp ages, it changes in power and UV output.

*Did you keep the glass in front of the lamp? *
It increases the time 20%

*Distance from the lamp to stencil*
The wider the image, the farther from the stencil you have to be so the light rays will go straight and minimize undercutting. 

*Thickness of the stencil.* 
110 is thicker than 200 and needs longer and it is harder to penetrate with a 500w lamp.

Don't be discouraged, you just have to make an actual test.
Go to http://www.lawsonsp.com/exposuretest.php
and study how to make an exposure test.


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## Fluid (Jun 20, 2005)

Straight form the Ulano Product Manager. Doesnt get any better than that 
we use Ulano RLX. Its been good to us for the past 10 years so why fix it if it aint broke  Plus I like the way it holds halftones.


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## RichardGreaves (Nov 7, 2006)

Fluid said:


> We use Ulano RLX.


Think about trying TLX. It's the same emulsion with a different dye. It has a lighter color so it exposes 20% faster. The lighter color is easier to register, BUT, some people like the darker color because it is easier to spot pinholes.

Think about trying QX1. Same speed and dual cure resolution qualities as RLX & TLX, but, it is pre-sensitized at the factory and has a least a 1 year shelf life. No more mixing diazo. Buy in 5G to save money.


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## MANNYMARISCAL (Dec 5, 2006)

I've done the test before. I would expose my screens for 7 min with my halogen lamps and it would be perfect. But recently 7 min stoped working.


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## Fluid (Jun 20, 2005)

Sounds like the bulb is weakening and you need to expose longer. A true exposure calculator will get you where you need to be.


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## RichardGreaves (Nov 7, 2006)

MANNYMARISCAL said:


> I've done the test before. I would expose my screens for 7 min with my halogen lamps and it would be perfect. But recently 7 min stoped working.


If you expose your stencil to an amount of UV light and the stencil doesn't crosslink and resist water as you wash it out, means there was not enough exposure to UV light. 

Imagine I sat out all last night under the spot lights in my living room and still didn't get a tan......... 

Prove it to yourself. Take a coated screen and tape at positive to it. 

Tape 10 pennies over the image, but only on one side of the coin.

Prepare a flat surface outside near a door.

Take this screen outside and pull a coin off every ten seconds, then wash it out as usual. With Ulano QTX, you might not get that much time because it is very fast.


You need to at least get a replacement lamp and see if that fixes the problem.

A 500 watt fused quartz glass, halogen gas, tungsten filament lamp is about 1/12th the power of the sun at BEST. Quartz glass is used for lamps because it can withstand high temperatures and lucky for us, UV is not blocked. Beware, some manufacturers add a coating of UV inhibitors on the quartz glass that effectively filters UV radiation for household use.


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## jlcanterbury (Jul 26, 2007)

MANNYMARISCAL said:


> I am using 500 watts halogen lamp to expose my screens. The screens are 19x22 110 mesh. What’s a good time to expose my images?



I have used a 500 Watt halogen lamp as well, and I found my best results were 13 minutes, with the lamp positioned 16 inches above the screen. Seems to work very well with 110 mesh.


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## mizi117 (Mar 12, 2007)

jlcanterbury said:


> I have used a 500 Watt halogen lamp as well, and I found my best results were 13 minutes, with the lamp positioned 16 inches above the screen. Seems to work very well with 110 mesh.


mine is similar as you. sometime i just only need about 10 minutes to expose; just make sure the emulsion is not too thick


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## macmiller (Jul 23, 2007)

opacity of the positve and humidity vary exposure times, too.

how are y'all getting 1yr out of qx1? i only seem to get 6-8 mos, but i probably need to put the top on tighter!!


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## RichardGreaves (Nov 7, 2006)

macmiller said:


> how are y'all getting 1yr out of qx1? i only seem to get 6-8 mos, but i probably need to put the top on tighter!!


There is no diazo to mix in, so there is no degrading of the sensitizer.

Pre-Sensitized emulsions aren't effected by water, and actually get a little faster as they age.

Yes, if you let it get crusty or dried out, that's neglect.

What happened to you that you know your QX-1 went bad?


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## gakleinjr (Apr 28, 2008)

does water stop cross linking while you wash out the stencil? it seems i may be exposing my screens too long and can't wash them out. could the reason be that the light in my wash out area is to bright and is overexposing my screen?


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## RichardGreaves (Nov 7, 2006)

*Positive, failure*



gakleinjr said:


> does water stop cross linking while you wash out the stencil? it seems i may be exposing my screens too long and can't wash them out. could the reason be that the light in my wash out area is to bright and is overexposing my screen?


*Stencils are easy.*
Stencil doesn't stay in the mesh - it wasn't exposed with enough UV-A energy, so it dissolves with water and rinses down the drain; just like it is supposed to.

*Image area doesn't wash out*
If the image area it doesn't wash out, it was somehow cross-linked with heat or UV-A energy, this usually means your positive failed to stop UV energy from reaching the stencil.

*Dime Complete Opacity Test*
To judge if your positive completely stops UV energy, tape a dime or a piece of aluminum foil to the stencil to see if the dark areas of your positive are failing you and letting UV-A energy through to the stencil. If the area covered by the dime doesn't wash out, you have exposed the stencil to UV energy or heat energy when you dried & stored it and the stencil resists dissolving with water and going down the drain.

Sounds like the emulsion is performing well, but, *your positive has failed you*, and UV energy moved through it. 

It is very unlikely that any room light, (if your wash out area is not safe), exposed your stencil in the 2-3 minutes it takes to develop it. Test this by coating a small amount of emulsion on a screen and when it is dry, take it to the sink and time it as it dissolves.


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## SarahConnor (Mar 22, 2015)

My exposure unit is halogen bulbs in a light tight box. The screen sits directly onto the glass. 
If you've got experience with this setup, how much time did you expose your screens? Thanks!


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## RichardGreaves (Nov 7, 2006)

SarahConnor said:


> My exposure unit is halogen bulbs in a light tight box.
> 
> The screen sits directly onto the glass.
> 
> If you've got experience with this setup, how much time did you expose your screens? Thanks!


I encourage you to re-read the earlier posts for guidance except my link to the exposure lesson I made when I worked for Lawson Screen Products. It doesn't work anymore.

You mention bulbs. How many and in what layout? How far are the lamps from the glass? 

Did you use work lamp housings? If so, did you remove the UV filtration safety glass? 

Multiple lamps means undercutting of the image, BUT that's not a concern if you only print bold designs.

What of hundreds of different speed emulsions did you use? What mesh and how thick is the coating?

A "light tight" "box" won't have any effect on your stencil curing time.

If you're printing water-based ink it's critical you completely cure the stencil. Water can break down or dissolve raw stencil on the ink side of the screen. Plastisol is like salad dressing and won't harm poorly cured stencil.

Harsh cleanup solvents can lock raw stencil into the mesh though. Under cured stencils can also be harder remove when you want to reclaim mesh.

Search this forum and read entries about "manual step test" and the US$10 "21 Step" for how to test and stencil cure. http://www.t-shirtforums.com/search.php?searchid=13368697









When I last checked, I have more than 130 posts on the Stouffer 21 Step Gray Scale that simulates 21 exposures every time you make a screen. Monitor stencil cure by put it on every screen you make for the rest of your life.


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