Author Topic: Emulsion Which one?  (Read 2568 times)

Offline ABuffington

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Re: Emulsion Which one?
« Reply #30 on: April 23, 2018, 11:51:31 AM »
Thanks for some of the great comments on T9 here.  American Niagara carries it out of Atlanta, or PM me with your location and I will help you find it closer than that if you need to.  While we can expose most emulsions with UV light, times can vary widely.  The strength of the lamp itself or source needs to be evaluated.  Many fine LED units out there as well as Metal Halide.  Post exposure helps T9 achieve even more strength, or a strong initial exposure works as well.  Complete cross linking of the emulsion occurs with strong UV light, or close proximity as is found in most LED units.  The longer the exposure needed, the more undercutting of halftones and details, and any lowering of time results in underexposure.  Underexposure will never be as strong as an initial complete exposure.  Post exposure and hardening become a band aid of sorts to underexposure, but can be needed with low wattage systems.
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com


Offline lancasterprinthouse

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Re: Emulsion Which one?
« Reply #31 on: April 25, 2018, 08:06:53 AM »
you went from a 15 second burn to a 90 second burn correct?  That's a 500% increase in exposure time.  If you were to see it just double... something would be wrong.  This is much more than that.

Emulsion is the same?

Screen mesh the same?

Screen mesh COLOR the same?

Emulsion thickness the same?

Dry box the same?  Dry box HUMIDITY the same?

Environment the same?  Environmental Humidity the same?

Films the same?

Film density the same?

Exposure unit glass the same?

SOMETHING changed.  You were getting amazing screens in 15 seconds.  Now you are not, at 500% more time.  What changed in your processes?  What changed in your equipment?

Now, are the cold nights, DRY nights?  or Moist nights?  If you don't already, get a hygrometer so you can check your relative humidity.  Screens (well) above 40% moisture will never be as good as screens below 40% moisture.  You will experience breakdown because a screen was not properly dry enough.

Before switching emulsions (to an emulsion that I love btw) make sure your screen room is following proper procedures and steps to make sure you have an optimal screen for exposure :)

I made an assumption earlier that your screens were properly dried and in optimal condition to be exposed for waterbase.  Lets make sure they are and then work backwards to fix the problem.

The only thing I can think of that changed other than the weather was going from standard mesh to s-mesh on most screens. Other than that, everything has remained the same from stencil thickness to films to ink prep cleaners and degreasers. I have to be honest though, I dont have a hygrometer and know that I need one. Our screening room is a 10x24' room that is walled off from the rest of the shop and has heat. I have put a dehumidifier in there before when the heat is on and it doesn't even run when I set it to 35-40% so I am assuming that our humidity level is below that. I need to get a better grip on the outside weather and our inside temps and humidity levels. I think Im going to pick up a hygrometer/thermometer this weekend and get them mounted up and pay close attention to them over the next couple of weeks.

Offline mk162

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Re: Emulsion Which one?
« Reply #32 on: April 25, 2018, 08:09:33 AM »

Offline Colin

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Re: Emulsion Which one?
« Reply #33 on: April 25, 2018, 08:29:44 AM »
Yea, S mesh definitely holds more emulsion.

Do you have fans set up to help circulate the dry air better?  If not, I would look at a way to set that up.

And always have your dehumidifier on - just in case.

Offline lancasterprinthouse

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Re: Emulsion Which one?
« Reply #34 on: April 25, 2018, 04:58:02 PM »
Yea, S mesh definitely holds more emulsion.

Do you have fans set up to help circulate the dry air better?  If not, I would look at a way to set that up.

And always have your dehumidifier on - just in case.

I have an overhead fan that and the heater is ceiling mounted. The idea was that the heat blows into the fan and then the fan pushes it down and around. My screens feel dry to the touch and Iíve never had films that ďstickĒ but is there a more scientific way of determining if they are in fact dry? Iíve had screens dry for hours up to a day or more and still get some breakdown on longer runs. Mostly at squeegee corners which is an easy fix by taping the squeegee paths but on some of the longer runs the image itself breaks down from time to time. Iíve been using liquid hardener but itís a time consumer and obviously an added expense. I need to figure out my situation so I can get back to trouble free screens from the gate.


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Offline Colin

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Re: Emulsion Which one?
« Reply #35 on: April 25, 2018, 06:40:53 PM »
That Hygrometer will put you miles ahead.  Knowing your humidity is HUGE when it comes to making a proper waterbase stencil. 


If you can, pop for a tool that measure the moisture IN your emulsion.  Most shops (like mine) do not have that and go by the relative humidity and general knowledge of their environment.

Offline ABuffington

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Re: Emulsion Which one?
« Reply #36 on: April 25, 2018, 07:31:02 PM »
To confirm:  S mesh holds a lot more emulsion.  Coat T9 with a sharp edge, 1:2 is maximum, 1:1 for halftones is typical on mesh above 200.  Drying screens is important so have a a humidity/temp gauge (hygrometer) is very important in the screen room.  A humidity reading of 90% basically is soaking your screens in water.  We shoot for 35% humidity and 72-80 degrees in the room.  Heating and air conditioning help as well for year round control of your room.  If unavailable a dehumidifier, space heater, fan and a temp+humidity gauge work wonders in a screen room, the larger the better for storage.  Keep sink/water/reclaimed screens out of the screen coating and storage room.  Dry Screens/the max exposure possible with good details/post expose and drying well, create super durable high res screens with Murakami T9.
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com

Offline lancasterprinthouse

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Re: Emulsion Which one?
« Reply #37 on: May 14, 2018, 08:47:16 PM »
Yea, S mesh definitely holds more emulsion.

Do you have fans set up to help circulate the dry air better?  If not, I would look at a way to set that up.

And always have your dehumidifier on - just in case.

Good news bad news.

Been using the Murakami T9 and my exposure times are back to 15-30 seconds. Post harden for a minute and I have a nice solid stencil for wb/dc.

Bad news is that now my films are sticking like crazy. To the point where it just took me 5 screens to make 2 because the film ripped the emulsion off the screen. Iíve read that diazo emulsions can have this issue and baby powder is a band aid. I havenít tried baby powder and really want to solve the issue without a band aid.

Iíll be honest, I slacked on the hygrometer so I have one ordered, finally. I will say that emulsion feels tacky so Iím guessing my humidity is too high but itís puzzling because the Crycoat (Saati PHU I believe) dried within 20 minutes in the same settings now it takes over a day for the T9 to dry and itís still tacky. Then again maybe the Cryocoat was never actually dry and that was my issue. Wasnít tacky at all though so Iím stumped at the moment.

1/1 coating on both emulsions.


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Offline Colin

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Re: Emulsion Which one?
« Reply #38 on: May 14, 2018, 08:50:55 PM »
Yes.  The stickiness when the exposure unit gets warm is normal with many emulsions, including Murakami.  It is suggested to use a very fine layer of talc/baby powder to help with that.

Part of why I used PHU for 4 years until I got my starlight unit without glass.

Offline lancasterprinthouse

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Emulsion Which one?
« Reply #39 on: May 14, 2018, 10:35:31 PM »
Yes.  The stickiness when the exposure unit gets warm is normal with many emulsions, including Murakami.  It is suggested to use a very fine layer of talc/baby powder to help with that.

Part of why I used PHU for 4 years until I got my starlight unit without glass.

I have LED.. didnít think it got that hot? I donít even need tape to hold the film on so Iím thinking my humidity levels are still to high. Theyíre sticking before burning.


Update: Got the humidity level down to 35% (according to my dehumidifier) and film only stuck post-exposure.



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« Last Edit: May 14, 2018, 11:06:33 PM by lancasterprinthouse »

Offline screenxpress

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Re: Emulsion Which one?
« Reply #40 on: May 14, 2018, 11:01:16 PM »
baby powder is a band aid. I havenít tried baby powder and really want to solve the issue without a band aid.

I use a light sprinkling of baby powder all the time and spread around with my hand before attaching the film.  I started doing that for exactly the reason you mentioned.

Has not had any negative impact in my exposures whatsoever.

If that's a band-aid, I'll take a box of Curity flesh colored strips.  :)
Anything important is never left to the vote of the people. We only get to vote on some man; we never get to vote on what he is to do.  Will Rogers

Offline Colin

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Re: Emulsion Which one?
« Reply #41 on: May 15, 2018, 08:22:17 AM »
Yes.  The stickiness when the exposure unit gets warm is normal with many emulsions, including Murakami.  It is suggested to use a very fine layer of talc/baby powder to help with that.

Part of why I used PHU for 4 years until I got my starlight unit without glass.

I have LED.. didnít think it got that hot? I donít even need tape to hold the film on so Iím thinking my humidity levels are still to high. Theyíre sticking before burning.


Update: Got the humidity level down to 35% (according to my dehumidifier) and film only stuck post-exposure.



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My starlight will get warm.... on a 10 second exposure.  So yea, those LED's can put out some heat.

How are you doing your post exposures?  I am confused about how your film would stick during a post expose?  A "post" expose is after you expose/rinse/fully dry an image.  Its best when the screen is turned over in your unit so the light hits the squeegee side of your screen - cross linking any residual polymers left in the emulsion.

Offline ABuffington

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Re: Emulsion Which one?
« Reply #42 on: May 15, 2018, 11:18:05 AM »
Humidity can also promote tackiness on the emulsion.  Baby powder or talc, just a tiny bit spread on the emulsion prevents stickiness.

Al
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com

Offline lancasterprinthouse

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Re: Emulsion Which one?
« Reply #43 on: May 15, 2018, 12:14:14 PM »
Yes.  The stickiness when the exposure unit gets warm is normal with many emulsions, including Murakami.  It is suggested to use a very fine layer of talc/baby powder to help with that.

Part of why I used PHU for 4 years until I got my starlight unit without glass.

I have LED.. didnít think it got that hot? I donít even need tape to hold the film on so Iím thinking my humidity levels are still to high. Theyíre sticking before burning.


Update: Got the humidity level down to 35% (according to my dehumidifier) and film only stuck post-exposure.



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My starlight will get warm.... on a 10 second exposure.  So yea, those LED's can put out some heat.

How are you doing your post exposures?  I am confused about how your film would stick during a post expose?  A "post" expose is after you expose/rinse/fully dry an image.  Its best when the screen is turned over in your unit so the light hits the squeegee side of your screen - cross linking any residual polymers left in the emulsion.

I can see how the way I worded that was confusing. I meant when I put my screen on the unit for exposure the film is not sticking but when I go to remove the film AFTER exposing it is sticking. So I suppose there is enough heat being generated during exposure to make it stick


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