# emulsion + exposure newbie help



## Six (Oct 10, 2007)

Hey guys,

I’m new, so first off... Sorry 

Now that's out of the way hopefully someone can help.


I have attempted a few emulsion jobs over the last 3 days and I'm still having some issues.

I'm using Ulano 925WR Emulsion.

Heres the go so far

Attempt #1 

1 thick coat of emulsion, about 3 hrs to dry 35 second exposure to sun.

Outcome:

Sadly, I'd say this has been the best result so far, seemed to work but lettering was not sharp and I lost some of the inside of an 'e'



Attempt #2 

1 single coat of emulsion, left overnight to dry 50 mins exposure with 200 watt light bulb.

Outcome:

Worked hard to scrub out but rest of emulsion started to come off also.



Attempt #3

1 single coat of emulsion, about 2 hrs drying time, 20mins with halogen light (the ones on stands you can get from bunnings for about $30).

Outcome:

Worked hard to scrub out but rest of emulsion started to come off also.


Attempt #4,

1 single coat of emulsion, about 3 hrs drying time, 35 second exposure to sun.

Outcome:

Seemed ok, but pressure blurred text and washed of some emulsion.



Before I start attempt 5...


Here is my theory, (oh the different light sources was to try some alternate methods if it’s raining etc and more for my own trial and error).

I am thinking towards the end I have not been letting my coasted screens dry long enough with the emulsion before exposing, that’s easy fixed.

My main concern is that I want the text to be strong and I need definite lines in the artwork so there is no blur, strong, sharp etc.


I have been doing the emulsion slightly blind in a dark room and that’s where I let it dry. I read on the forum a light bulb with yellow coating will be safe to use, might help me see what I'm doing too.)

What would you guys suggest?

Thankyou all for the help

Cheers
6


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## Solmu (Aug 15, 2005)

Sounds like you're not exposing for long enough (hence the emulsion that should be exposed washing off). Alternatively you're exposing for too long (the unexposed emulsion shouldn't be that hard to wash off) and managing to scrub off exposed emulsion along with less exposed emulsion.


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## Six (Oct 10, 2007)

thankyou,

what whould you suggest is a good exposure time for direct sunlight?

is there a link somewhere showing different times etc for diferent light sources?


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## Solmu (Aug 15, 2005)

Six said:


> what whould you suggest is a good exposure time for direct sunlight?


I've never done it, so I don't know. If you have a look at some of Richard Greaves' posts about exposure in the screenprinting section, he has lots of good info on how to calculate a correct exposure time.



Six said:


> is there a link somewhere showing different times etc for diferent light sources?


I've never seen one, and wouldn't trust one if I found it. There are too many variables: who manufactured the light source, how old is it, how thick is your emulsion, who manufactured that, etc. etc.


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## Six (Oct 10, 2007)

okies thankyou.

I have found my exposure table and can figure out calcs.


But What category would halogen light be under, been so long since science at school.

On the back of the lamps I want to use it says 2 x 500 watts. I was thinking of killing one ie using one pointed at the scource. I assume this means 1 is still 500 watts ie not 250 by itself.

anyway, what is the bulb classified as from this list.:- 

?


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## rusty (Feb 9, 2007)

When you say "scrub", does that mean you are trying to scrub out your emulsion after exposing?


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## RichardGreaves (Nov 7, 2006)

The spirit drums from down under called to me from Solmu - "Help, help".




Six said:


> I have found my exposure table and can figure out calcs.
> 
> But What category would halogen light be under, been so long since science at school.


The sad news is: quartz halogen lamps are not recommended and not listed. You will notice the sun is also not listed or incandescent bulbs from your reading lamp. - or my father's old spotlight from the car.

It is your sworn duty as a screen maker to learn to make an exposure test. Spend $45 now and buy a $10 transmission 21 step gray scale and an exposure calculator from ANY emulsion manufacturer. Properly used they will last a lifetime and stop a lifetime of guessing. One exposure with a Stouffer 21 Step Gray scale where you hold a solid step 7 in the mesh, and you will know more than anyone else in the world what is going on in your shop. Looking back, would you spend $45 to have your 3 days and 3 screen back? With a gray scale, you can also tell people over the phone, what step number you are measuring with your scale and they will know what you are talking about. The scale has no friends. It will judge sun and halogen lamp the same. 

More sad news, it's not good science to make one exposure, fail, and then switch to a completely different light source and start from scratch.

A stepped exposure test is just like learning to cook anything, from marshmallows to 6 course meals. You cook for a little time and then check, then cook a little more and check, then cook a little more and then check.

A slide show and a downloadable video are available at:
Support Menu of Screen Making Products

Download the direct emulsion video under the General tab.

You are also using a industrial strength water resistant emulsion that is not very fast, because to get that maximum water resistance, it has to be completely crosslinked. 

The sun can be very strong, but it changes every 10 minutes and this afternoon it was cloudy. 

Then you switched to a 200 watt bulb that has no promise of UV energy at all if it is incandescent.

Then you switched to a quartz halogen lamp that comes from a Mysterious place called "bunnings".

There are many variables, but exposure is easy to test. Search for "exposure test" in these forums.

You also need the ying to the yang of the exposure, the positive that is blocking the UV energy from cross linking the stencil so it dissolves with water and rinses down the drain. Yo must have a good positive. "Scrubbing? " There's not scrubbing out the image area in screen printing!

Emulsion is easy. If it rinses out of the stencil, it didn't get enough exposure to hold onto the mesh. If it doesn't wash out, something cross linked it and it holds in the mesh.



Six said:


> On the back of the lamps I want to use it says 2 x 500 watts. I was thinking of killing one ie using one pointed at the scource. I assume this means 1 is still 500 watts ie not 250 by itself.
> 
> anyway, what is the bulb classified as from this list.


I have to guess that you bought a lighting fixture that is expected to hold 2 500 watt lamps. That means 500 watts of expensive electricity and plenty of WHITE VISIBLE light coming out, but UV energy is usually undesirable because is bleaches you girlfriends drapes and burns you eyes out over time, so manufacturers coat them with UV filters or filter the light with plain glass that does a nice job of filtering UV energy. 

Search the forums for 'halogen'.

Often these lamps do put out SOME UV energy, but you could expect exposure times from 13 to 25 minutes. Only a test will tell.

925WR is a great emulsion, but when you pair it with low energy lamps, you have a slow exposing emulsion.

Search the forums for "925WR" for more comments on that emulsion.

In the USA, unless you are picking up the 925WR from the distributor, you are paying a 20 UPS hazardous materials fee because of the Mild, mild acid content of the syrup diazo sensitizer. Most hobby shops use TX from the Ulano product line because it uses powdered diazo sensitizer. Ulano also makes a much faster exposing modern emulsion called QT-Discharge. Don't let the discharge name scare you away.


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## Six (Oct 10, 2007)

thanks guys, when I say scrub I propbably shoudl have said rub with my fingers, thats all.

richard, thankyou above and beyond.

will stick to one method to get a test first.

what type of light would you recommend that I can get away with on the cheap side for now that will do the job of something listed on the data above?

cheers again
6


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## Six (Oct 10, 2007)

oh, also there was a tute on youtube showing another way to do a step test, will this work

http://http://youtube.com/watch?v=GPbt5vy68_k&mode=related&search=


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## RichardGreaves (Nov 7, 2006)

Six said:


> what type of light would you recommend that I can get away with on the cheap side for now that will do the job of something listed on the data above?


Fluorescent 40 watt Unfiltered Black Light lamps, close together and close to the glass.

Put a dime on your screen the next time you expose. This will show you how a real positive blocks UV-A energy so it doesn't leak through and cross link the stencil in the image area.


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## Six (Oct 10, 2007)

thankyou , you have made this so much easier,

I have created an image i will be using to help me with a step test.

http://img36.picoodle.com/img/img36/9/10/10/f_calabm_d263be5.jpg

might come in handy for other users.

when you say black light lamps, do you mean the ones that show up glow in the dark stickers etc? could you link to a piccy so I know what im looking for. if they are what you mean, can you think of anythign cheaper to start 

again thankyou.


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## RichardGreaves (Nov 7, 2006)

As part of your homework, you should search these forums for "black light".

TopBulb.com - Product List


I think you can assume everyone understands and suggests the most economic solution they know, rather than assuming we know a less expensive product, but aren't going to tell you so you can figure it out yourself.


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## Solmu (Aug 15, 2005)

RichardGreaves said:


> I think you can assume everyone understands and suggests the most economic solution they know, rather than assuming we know a less expensive product, but aren't going to tell you so you can figure it out yourself.




Well put. I'm tempted to stick that in the faq


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## Six (Oct 10, 2007)

fair enough 

thankyou.

The black lights i knew of where something like $200 each.


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## Six (Oct 10, 2007)

hey guys, thanks for the info.

just bought 2 black light fluro tubes and set the timer as per above table.

Emulsion came out easier then before, (which leads me to believe I left it way too long last time).


however I couldn't see the non design washing out but my lines are chipped, ie I dont have strong lines in the artwork, specially the lettering. Does this mean I have left the exporure too short? or would you say it may be the stencil... ie I am using overhead transparencies with laser printed ink on them.

suggestions?

thanks again.
6


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## rusty (Feb 9, 2007)

It would help a lot if you could post a closeup picture of what's happening.


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## RichardGreaves (Nov 7, 2006)

Six said:


> ie I am using overhead transparencies with laser printed ink on them.


Laser toner is notorious for not being a good UV energy stopper, except for the Xante ScreenWriter that is designed to deposit more than usual deposit and has higher fuser temperature than average office lasers.

To work for screen printing, media has to be textured - that's why we use transparent paper with a vellum finish and polyester film must be textured. Overhead transparencies do have a mild texture on one side, but nothing like the texture on commercial laser film or paper for screen making. 

If you can't find a top quality positive, you might use India ink on a clear film for hard sharp edges like we used to do in the olden days. Examine your image edges with a magnifying glass to see if you have hard sharp edges.

2 lamps will cover about 6 to 8 inches of coverage at 4 to 6" from the glass.


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## Six (Oct 10, 2007)

thanks guys, I was using vellum before but changed as I thought it was the issue originally.

here is a pic of the screen which shows what I am talking about re edges not being sharp. I think I will retry one of my designs on the vellum to see how that goes.

heres the text, so sharp as you can see 












and the pic itself


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## rusty (Feb 9, 2007)

I'm certainly no expert on liquid emulsion (which is why I use capillary film), but it could be 1) the film is not making good contact with the screen, or 2) over-exposure where the light is penetrating behind the image. Of course it could be something else too, but it looks like portions of your image on the edges are getting exposed to light when they should not be.


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## Six (Oct 10, 2007)

ok guys, thankyou all for the help,

I figure the best bet is to upload a few photos of my setup to try eliminate any other possibilities, just had a new problem. I put a coin on the glass to do a uv test as richard suggested and it seemed ok, problem I had this time is I left the emultion dry overnight, the exposure time was as suggested in the table, 4:48 seconds, ok maybe i did 4:40 but will 8 seconds really make this much difference.

The coin spot washed out fine, the stencil spot also seemed ok, but it also took some emultion out with it, ie leading me to believe the exposure time was not long enough, used a vellum paper stencil.

I'll explain the photo's maybe it will help..











1 inside of my screen
2 front of my screen
3 stencil taped down on glass also shows black light setup
4 black light setup to show distance from lights
5 another shot of my exposure setup
6 yet another shot of exposure setup
7 showing how I put the screen on (the screen isn't actually in the photo, but I put a blackshirt in behind the screen, put a piece of timber on it and weight it down so I have positive contact.
these photos were taken with a flash so usually the room is dark.

suggestions?

cheers
guys.


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## Six (Oct 10, 2007)

cheers, will give the weights a move and try taping to screen rather then glass, black shirt is as you suggest, behind the screen.

thanks will update


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## Six (Oct 10, 2007)

will do going to go for 12 mins, my only concern is the amount of pressure i'm having to use,

also we here in australia have water restrictions now due to bad planning.

I guess a typical spray bottle wouldn't be anough pressure to remove the emulsion after exposure?


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## Six (Oct 10, 2007)

okies, looks like it has to do with positive contact, i always thought i had good contact, tried 12 mins and it washed out ok, some emulsion still came off but i had a few blurry lines,

tried 18 minutes and all good, apart again from a blurry line at the very end, my guess is to use smaller weights to make sure ALL of the paper is down and next one should be a success at 18mins.

will keep you posted, unless you can think of an easier way for me to setup with what I have available.


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## Six (Oct 10, 2007)

i think the reason I;m having contact issues may be the tension of my screens, any tips to making home made screens that doesnt take a genius to create, lets just say my manual skills are a little lacking


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## rusty (Feb 9, 2007)

1) Just buy a professional screen, preferably aluminum. That will help a lot in getting good positve contact. They are cheap.
2) According to your pictures, it doesn't appear you are putting any pressure on the mesh itself. If you are just pressing the frame onto the glass, you are not getting good contact, ESPECIALLY if you are using a homemade wood screen which is likely not perfectly flat on the glass. You need a piece of foam that fits inside the screen, but is taller than the frame so that when you place the wood and weight on top, it presses on the foam (and mesh) rather than the frame.
3) If you are going to place the quarter on there, be sure it's between the vellum and the glass; not the vellum and the mesh. Placing it between the vellum and the mesh as shown in your pics would prevent your mesh from getting good contact with the vellum.
4) You do not need high pressure to wash out a screen. High pressure will wash out details that you do not want washed out. If exposed correctly, you only need to dissolve the unexposed emulsion. A typical water hose or shower head is plenty of pressure. Just be patient while it dissolves. Don't try to force it out.


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## sneakdesign (Aug 23, 2007)

Hi Six, I'm Australian as well - water restrictions are really annoying with screenprinting. What I do is get a bit of hose and connect my laundry sink drain back onto my hose attachment so it's the same water going around. Also, those hose attachments that look like guns are real useful for altering the pressure of your spray for stubborn emulsion. Go back to bunnings!


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## Six (Oct 10, 2007)

thanks guys, I'm going to try again tomorrow when i should according to ruling everything out have success, I have a piece of wood that was cut out of the frame (ie I cut my frame out of plywood so theres no joins,) don't have any foam so that will have to do for now, should still be enough to get positive contact.

be assured, i will post re result.

thanks for all your help.


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## Six (Oct 10, 2007)

ever get to that stage where you want to smash things?

I'm currently in that position

attempted with everything else as previosuly explained,

18 minute exposure,
wood holding image to mesh with weights on it, ie seperate part in the midde so weight on mesg not frame.
standard spray out

this is what happened










as you can see the lettering is crapy, the part in the middle of the gass mask was supposed to wash out also, ie holes in the mask, I also had a little emulsion wash off the right hand side of the logo.

please help, im at my witts end. and down about $300 to mention it


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## rusty (Feb 9, 2007)

If you are using a piece of wood in the center to push down the mesh, I don't think that's going to do very well. It needs to be something soft, like foam that presses all areas down evenly. Pressing a piece of wood on top of a piece of glass as you described will have areas with no pressure, which results in what you see above. You must have pressure over the entire image so that the film is pressed tightly against the mesh. Your picture shows that light is getting around your image between the film and and the mesh.


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## RichardGreaves (Nov 7, 2006)

Six said:


> as you can see the lettering is crapy, the part in the middle of the gass mask was supposed to wash out also, ie holes in the mask, I also had a little emulsion wash off the right hand side of the logo.


I don't think your positive is stopping the UV light. If it was, a 1 hour exposure would not leak UV energy to cross link your stencil. 

You might also have a problem because you only have 2 lamps, and the exposure might not be even. 

Exposure is easy. If it doesn't wash out and holds in the mesh, something cross linked it. If it washed out, it wasn't exposed enough.

Blurry edges is probably poor contact, but, it could also be the edges on your positive.

Your picture also shows poor coating which may come from that fact you have a small screen.


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## Six (Oct 10, 2007)

thanks guys, will try the foam and hopefully not injure something small


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## Six (Oct 10, 2007)

been a little busy, my wife ever so rudely gave birth to my first child (as if there is going to be a second ) which took up most of my time.

home now all is well, so it seemed to have worked this time around using the foam


have a few pinholes around the edges which is easily fixed with a cover over of emulsion.


will let you know how it goes trying to print..

thanks for all the continuing help.


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## Six (Oct 10, 2007)

thank you, the evil plotting has already commenced


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## Six (Oct 10, 2007)

ok, so here is the screen,

I'd say it was a success, and i'm happy










and here is the print, not exatcly satisfied as the lines are blurred, but thats all down to holding the screen by hand while printing and a loose mesh, overall I'm happy.










just coated 2 more (bigger) screens and will try expose tomorrow. thankyou all for your help.


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## rusty (Feb 9, 2007)

Looks like you are getting the hang of it. It just takes a lot of trial an error.


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## Six (Oct 10, 2007)

yup, made a second one and this time its pretty solid, again thanks for all your help guys


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## rusty (Feb 9, 2007)

Looks great! Good job.


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