# Quick fix for emulsion not washing out?



## web707 (Feb 2, 2009)

I coated both sides with Speedball Diazo coating the squeegee side last. Exposed onto the print side with a piece of glass on top. I exposed my vellum at 18" for 14 minutes. This was after I did a test exposure for different times. 14 minutes seemed to work the best. While washing out with a garden hose, I noticed I couldn't get all the image out. (spent about 20 minutes trying to get it out) Well, it won't wash out entirely. I thought, maybe it's ok and i tried it with ink, nope. The ink would not pass through all the areas. So, I was wondering if there was some kind of chemical (photo emulsion remover, or Acetone) or something I could use with a q-tip to clear out those areas? (quick fix) Just don't want to have to reclaim and expose again. I've attached pics for people to give suggestions on my question and on general setup. Thanks.


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## LaTonya (Sep 1, 2008)

Hi , I use 500w halogen lights,I do not use the speedball emulison, but to me you have over exposed the screen to long try exposing for lest time. I use Nazdar emulison and I burn my screens for 3 to 5 mins, and I uses a water hose to wash it out. I hope this will help.
LaTonya


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## web707 (Feb 2, 2009)

Thanks, just curious, if you expose for only 3 to 5 minutes, what height are you exposing at?


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## LaTonya (Sep 1, 2008)

I stand my screens up not on the floor, it is about 20 inches away, so 18inch should
be okay, but try 5mins and no more.
LaTonya


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## chuckh (Mar 22, 2008)

I' going to guess that you are over exposing your screen and/or your positive (vellum) is not dense enough. Sometimes if your image does not involve a lot of fine detail, you can rub the image area clean by using you fingers and warm water without destroying the stencil .


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## web707 (Feb 2, 2009)

I may be over exposing. I'm going to try again with 5-7 minutes. The vellum prints very dense. I was worried about it at first, but spent plenty of time figuring out how to print dense on vellum. So, it's not that.


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## RichardGreaves (Nov 7, 2006)

*Positive is failing to stop UV energy*

If the stencil doesn't wash out, it was crosslinked somehow - either UV light, stray light in your shop or too much heat (110F+) for several days.

Your positive probably failed you and UV energy got through it.

Next time you expose, tape a *dime *to an unused area of the stencil as a proof. No UV energy will penetrate the dime and it should dissolve like a dream. If your image area doesn't wash out the same way, your velum positive is weak.


In the middle of you setup, your lamps overlap, doubling the exposure - in the middle.

Remember to remove the protective glass. It's there to stop UV energy from damaging your eyes and filters it.

Learn to make a step test to determine exposure time.
http://www.ulano.com/video/UlanoExposureTest.256k.wmv

Exposure FAQ Screen Making Products how to measure exposure

Use a fast exposing SBQ emulsion to compensate for your low UV light source.

It is common to learn how to run the same vellum through the manual feed of your laser printer twice for enough density.


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## web707 (Feb 2, 2009)

*Re: Positive is failing to stop UV energy*

Thanks Richard. I will try the dime test. I am exposing without the protective glass. Someone earlier told me to try no more than five minutes, but I didn't chose to believe it and exposed for 6.5 minutes and got the same results(not washing out) On the positive side, most of the stencil washed out fine, so I know I'm on the right track. Gonna try a wedge test also before I waste any more emulsion. I only have enough for one more screen(if that). Think I'll make 5 minutes my max. (Thanks, LaTonya) I've also read that many people here like Ulano QTX- I'll look into it for the next batch.


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## RichardGreaves (Nov 7, 2006)

*Re: Positive is failing to stop UV energy*

You have no fine details. Don't worry about overexposure.

I wrote 2 posts in this thread yesterday:
http://www.t-shirtforums.com/screen-printing/t75851-2.html#post455791

this one is about overexposure which is usually confused with undercutting or light scatter.


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## Greatzky (Jan 28, 2009)

don't mean to threadjack, but i feel like i'm getting symptoms of a few things with my screens.
I think it might be the non dense transparencies that i'm using(i am just printing transparency setting with a lexmark 1300 for now).
I exposed for 13 full minutes with a standard exposure unit(500watt light (kit from silk screening supplies) and even took the glass off. I didn't know you were supposed to take the glass off until I read up on here and saw that it said UV protective glass.
When I wash out The screen gets some suds and also I see the yellow diazo drip a bit. The Image took a while to blow out and I had to use the jet setting on my garden hose attachment. The screen actually looked burnt this time(I guess becuase of the lack of UV glass). I even put foam underneath the setup to try and push the screen into the transparency and glass for positive contact. I put a dark sheet between the foam and screen to prevent any light from bouncing back.
The washout took a while and towards the end I almost lost a part of the design. The design didn't bubble up like the last 2 times that I exposed screens, but It just isn't the same as it used to be.

I just bought new emulsion and I made these screens only about a week ago. They were dried completely and stored away in a lightsafe and room temperature area.

I'm just not sure what exactly is the problem as I feel like i'm getting underexposure symptoms as well as over/light scatter. 
I'll have to post some pics soon and start my own thread perhaps...
Sorry for the threadjack.

-Scott Lewis


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## RichardGreaves (Nov 7, 2006)

*Most printer positives are not very opaque to UV energy*

After washing out the image area, feel the screen on both sides with your fingers. If the texture of the stencil is different on the inside, compared to the bottom, UV energy didn't penetrate and the inside is underexposed. Imagine only cooking a hamburger on one side.
*
Dime Complete Opacity Test*
To judge if your positive completely stops UV energy, tape a dime 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 or piece of aluminum foil doesn't wash out, you have exposed the stencil to UV energy or heat energy and the stencil resists dissolving with water and going down the drain.

Cut a simple random pattern out of aluminum foil and use it to compare to your positive. It will have razor sharp edges and will stop all UV energy.

For fine lines, test this by taping different thicknesses of wire to an unused part of your stencil. The metal wire will not allow UV energy to transfer through it like a poor stencil.

*21 Step Transmission Test Positive*
The best exposure test is a Stouffer 21 Step Transmission Gray Scale. A transmission gray scale is a small film positive with darker and darker filters next to each other in steps. When you have one on the stencil as you expose you will get a simulation of 21 different exposures to the stencil and you get visual feedback that shows you how well your stencil is exposed.
Printer Information and Training for Screen Printers
Exposure FAQ Screen Making Products how to measure exposure

When you wash out the stencil, areas that didn’t get enough exposure will dissolve with water and go down the drain. You want a minimum of a Solid Step 7 that doesn't dissolve and go down the drain. More exposure will make your stencil more durable and less will make the stencil less durable.

When you put a gray scale on every screen, you will get *visual feedback* of the invisible action or cross linking and you will notice when it washes out differently and you will know your lamp or stencil is different and you have to change your exposure.


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## mrvixx (Jan 13, 2009)

remove the glass from the worklights and lower exposure time to like 5 mins


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