# Emulsion



## Byeline666 (Oct 21, 2006)

i have been using *CCI DXP Diazo-Photopolymer Dual Cure Direct Emulsion* and my supplier just recently recomended me *SaatiChem PS2 Blue* emulsion. 

he said its blue and it doesn't need to be sensitized. also that its unlimited shelf life and exposes twice as fast. 

first of all i have always thought that blue emulsion was for graphic printing. just wanted to know if anyone has any experience using this type of emulsion and if its really as good as it sounds.

thanks.


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## RichardGreaves (Nov 7, 2006)

Byeline666 said:


> i have been using *CCI DXP Diazo-Photopolymer Dual Cure Direct Emulsion* and my supplier just recently recomended me *SaatiChem PS2 Blue* emulsion.
> 
> he said its blue and it doesn't need to be sensitized.
> 
> ...


There is some basis for saying that red colored emulsions resolve an image better, but only under the best exposure and coating conditions. Check any listing from any emulsion company (including Saati) and you will see a range of colors from blue to red and others in between. Blue emulsion is not for graphic printing.

Pre-sensitized emulsion DOES NOT have an unlimited shelf life. 18 months to 3 years in controlled storage, but not unlimited.

Pre-sensitized emulsion are usually fast exposing and a favorite for beginning textile printers with inferior exposure lamps. Because of the long shelf life you can also save money buying in 5 gallon pails, not gallons.


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## sethm (Jan 17, 2008)

Hello Mr. Greaves, I've been using *CCI DXP Diazo-Photopolymer Dual Cure Direct Emulsion for a year and a half(since I started printing more). Its been fine. I like the stuff, but decided give some ulano QX-1 a shot. I need to know how to expose my screen with this stuff. I own a simple 500watt halogen light that sits 12" above my screen. The tech sheet with the QX-1 doesn't even include info on a 5OO watt bulb. I'm a novice at this stuff and find the tech sheet pretty intimidating....I guess I don't know the language. Please help me. Thanks!*


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## RichardGreaves (Nov 7, 2006)

sethm said:


> I've been using CCI DXP Diazo-Photopolymer Dual Cure Direct Emulsion for a year and a half (since I started printing more). Its been fine. I like the stuff, but decided give some ulano QX-1 a shot.
> 
> I need to know how to expose my screen with this stuff. I own a simple 500 watt halogen light that sits 12" above my screen.
> 
> The tech sheet with the QX-1 doesn't even include info on a 5OO watt bulb.


QX-1 emulsion is no faster than other dual-cure emulsions.

Alas, nobody can help you make an exposure test in a forum or over the telephone. If I was magically transported to your shop, I would still have to make an exposure test because stencil coating thickness, mesh count, mesh color, dryness of the stencil, electrical power, the lamp type, the lamp power, the age of the lamp, the UV light range, the lamp distance, the glass type in your vacuum, the color of the vacuum blanket - all influence the exposure 'TIME'. 

The reason there is no 500 watt halogen lamp on the data sheet is because there are no industrial standard for the hundreds of lamps you could but. Many are coated with a UV filtering coating. 

A simple test with a 21 step gray scale or ANY stencil manufacturer's Exposure Calculator that will bracket your best exposure with 2 steps of UNDER exposure and 2 steps of OVER exposure so you can choose your favorite.

Biggest of these is the power of the lamp and how well the UV light penetrates the stencil. This is why more powerful is usually better. 

I have a video clip of an elementary exposure test on the Ulano web site:
Exposure FAQ of Screen Making Products It's about 4Mb. Judging exposure is the most elemental skill of a screen maker. 

Not all of the 500 watts that goes into your lamp, comes out as UV light. I'll bet your 500 watt lamp is very bright, (as are most lamps designed for use in living rooms). If they were good for UV exposure use in screen printing, I'm sure they would be illegal for use in living rooms. 

All that white light and infra-red heat are wasted when exposing UV sensitive stencils and much of the 500 watts of expensive electricity, is used to heat up the lamp to its super hot operating temperature. 


Exposure is not only 'time', it is a volume measurement. ??How long does it take to fill up a 1 gallon bucket with water?? Without knowing how big the hose is, *nobody *can calculate the 'time' it takes - but I can measure it in the 15 minutes it takes to make an exposure test.

QX-1 emulsion is no faster than other dual-cure emulsions, but it is pre-sensitized at the factory and has a shelf life of 18 months compared to 6 weeks.

Threads discussing exposure calculators and the 21 step transmission gray scale:

This post has an actual picture of exposed gray scales although the discussion is about exposing with the sun. All the posts add to the principles of measuring exposure and how to measure.
Exposure using the sun!??!

Exposure test with the Stouffer Scale? Lawson SBQ 510?

The longer the exposure time the better?
What Emulsion To Buy

Available at:
21 Step Sensitivity Guide - 301-905-1-EA
21 Step Stouffer Scale - SG21
Blue Hills Printing Ink and Litho Supply Corp.
21-Step Sensitivity Guide - HTC134


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## sethm (Jan 17, 2008)

Thanks! I appreciate the help. I'll do the step wedge test. I'm just being lazy. I think i'll start the first step at 6 minutes, half of what I did with my previous emulsion and then go from there.

thanks again-seth


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## jayjude (Jan 20, 2008)

hi! im just a beginner and want to know about emulsions exposure. if i'm using four florescent light with 20 watts each, how long do i have to expose the image? and why does the emulsion spreads after washing it with water after the exposure from light and image?


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## RichardGreaves (Nov 7, 2006)

jayjude said:


> I'm using four florescent light with 20 watts each, how long do i have to expose the image?
> 
> 
> and why does the emulsion spreads after washing it with water after the exposure from light and image?


There are dozens of different fluorescent lamps and emulsions, so nobody can tell you how long your exposure should be - you have to do an exposure test. Lamps have different UV energy output and emulsions have different sensitivity to UV energy.

UV energy cross links the sensitizer in the emulsion and it doesn't dissolve with water and rinse down the drain. If it washes out, it didn't get enough exposure.

Post #4 explains this in part, and there are many links for study included in that post.


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## jjjohnso1 (Mar 3, 2008)

Does anyone have a recomendation on where to buy ink and emulsion?


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## alan802 (Mar 24, 2008)

jjj, where are you located at? I am in Texas and have Graphic Solutions Group, River City Graphic Supply and McBee to chose from. All have great products and people. River City is in San Antonio and Austin, McBee is in Houston and GSG is based out of Dallas I believe but has a few locations in the southern states.

We use ChromaBlue and like it. Also, used KIWO dual cure for a while with good results also.

P.S. I just joined this site and everyone that doesn't know this already, listen to richard. He might be the smartest guy I've ever talked to over the phone. He knows his stuff better than anybody in the business.


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## TMOGUL (Jun 15, 2007)

RichardGreaves said:


> There are dozens of different fluorescent lamps and emulsions, so nobody can tell you how long your exposure should be - you have to do an exposure test. Lamps have different UV energy output and emulsions have different sensitivity to UV energy.
> 
> UV energy cross links the sensitizer in the emulsion and it doesn't dissolve with water and rinse down the drain. If it washes out, it didn't get enough exposure.
> 
> Post #4 explains this in part, and there are many links for study included in that post.


 Hello Richard i have a question. you said if the image washes out it is under exposed so is it safe to say that if the image doesn't wash out completely it is over exposed?


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## RichardGreaves (Nov 7, 2006)

*Where to buy screen printing supplies?*



jjjohnso1 said:


> Does anyone have a recomendation on where to buy ink and emulsion?


Where are you?

It is senseless to suggest a great distributor in Australia or Germany if that's not were you live or work.


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## RichardGreaves (Nov 7, 2006)

*Exposure question*



TMOGUL said:


> you said if the image washes out it is under exposed so is it safe to say that if the image doesn't wash out completely it is over exposed?


Did I write "under exposed", or "over exposed"? I strongly doubt it.

I described the chemical reaction that makes sensitizer cross-link and hold the stencil in the mesh. _
UV energy cross links the sensitizer in the emulsion and it doesn't dissolve with water and rinse down the drain. 

If it washes out, it didn't get enough exposure.

_You *want *image areas to dissolve with water and rinse down the drain, so ink can transfer through the mesh when you print. You cover the stencil with something that will block UV energy so that area is protected. 

Areas that are exposed to UV energy will cross link and if they get enough exposure, they will resist dissolving and rinsing down the drain.

The more exposure to UV energy, the more durable the stencil.

If the stencil breaks down during washout, it didn't even get the MINIMUM exposure required for the durability to stay in the mesh, much less hold up to the tortures of the squeegee blade, off-contact distance and ink. 

If the image area is hard to washout, I usually find the positive failed to keep the UV energy away from the photosensitive stencil. I use a dime to compare washout in a suspect positive, because a dime will stop all UV energy. Comparison is the source of all quality control.

Most people asking about initial exposure usually have not invested in the minimum tools necessary for feedback after exposure, the Stouffer 21 Step Sensitivity Guide, (US$7-15) and an exposure calculator to make simulated, bracketed exposures above and below you chosen OPTIMUM exposure to determine what is the fines line or dot your stencil material, mesh, lamp, mesh color, etc. can achieve.
http://www.t-shirtforums.com/screen-printing/t24239.html#post143704

Too many people under expose (which means a weaker stencil), so they can get finer lines or dots to render. Then they are disturbed when the stencil fails on the press or even in the sink.

Undercutting is what they are fighting. UV light can curve around the positive or bounce around in the mesh and stencil, "choking" fine lines and dots. 

This is Mother Nature and the lines or dots you make in a computer may not be able to be reproduced perfectly with your system - or any system.

Most fine lines or dots below .030" have to be thickened so they can survive the choking that 'naturally' happens during exposure.

If you want a .010" line, you may have to start with a .020" line first. Then you can fully cure and cross-link your stencil AND print a .010" line.


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