- How many washes can you do to a screen (with a burned design) before it will loose its details especially the edges and some critical areas? This concerns washing of screen everytime ink starts to clog the screen.
- After burning and washing out the design of the image, what can be done to the emulsion left on the screen to keep it on and still have the clarity of your design even after several washes?
Hope to have your answers to my questions. thanks a lot
Depends on the emulsion and how you are washing the screens each time.
You can after burning the screen and letting it dry, re burn or let it sit in the sun for a while 30 min to an hour. This post burn will help to harden the stencil a little more.
What type of inks are you using? If plasticols, clean out the screens using press wipe. This should make the screen/stencil last a little longer.
How many washes can you do to a screen (with a burned design) before it will loose its details especially the edges and some critical areas? This concerns washing of screen everytime ink starts to clog the screen.
- After burning and washing out the design of the image, what can be done to the emulsion left on the screen to keep it on and still have the clarity of your design even after several washes?
I of course, will take the aloof answer. I believe you are testing the waters with this question because you are afraid of something.
Properly exposed a stencil should last 50,000+ impressions.
Properly exposed and using a compatible solvent, there is no reason why a stencil should ever break down.
If your stencils breakdown, there is plenty you can do in pre-press to increase the durability of the stencils. It may be that you don't have the equipment to make screens for long runs. How long do you want them to last? With hardener, I could see a stencil lasting forever.
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How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
im using water base ink. im washing the screen only to the extent of removing inks. im not overwashing it. i just make sure that nothing will be left that might clog the screen.
to RichardGreaves,
i just want the screen to last until i will no longer need it. i worry that every washing might loosen up the emulsion and destroy some details in the image.
i just want the screen to last until i will no longer need it.
i worry that every washing might loosen up the emulsion and destroy some details in the image.
what solvent are you referring to?
Stencils do not 'age'. There is no reason that repeated cleaning would damage a screen, but what are your expectations of wanting a screen, "to last until i will no longer need it". Is that 2 weeks, or 20 years. I have screens in my office that are 20 years old.
"A compatible solvent" is a solvent compatible with your ink. Cleaning plastisol ink with a strong vinyl solvent, or MEK, or acetone can damage a stencil with poor solvent resistance. Every ink manufacturer suggests a proper solvent for cleanup in their instructions. If you use the wrong solvent (in your case water), bad things happen.
Cleaning a water based ink with water but using a stencil with poor water resistance will damage the screen. You didn't tell us how you are exposing your stencil or what actual stencil you are using.
If you under expose your stencil, and all the sensitizer is not crosslinked it can be damaged by almost any cleaning. Under exposing will also cause reclaiming problems because reclaiming chemicals attack the cross links that hold the stencil in the mesh.
At least 50% of the stencil trouble shooting calls I answer are based on screen makers using low energy light sources and not exposing long enough.
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How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
Stencils do not 'age'. There is no reason that repeated cleaning would damage a screen, but what are your expectations of wanting a screen, "to last until i will no longer need it". Is that 2 weeks, or 20 years. I have screens in my office that are 20 years old.
sorry, what i meant was for the stencil or the burned image on the screen. i experienced that after several washes, some details gets lost and washed out. excluding the pinholes that suddenly appear.
Quote:
Originally Posted by RichardGreaves
"A compatible solvent" is a solvent compatible with your ink. Cleaning plastisol ink with a strong vinyl solvent, or MEK, or acetone can damage a stencil with poor solvent resistance. Every ink manufacturer suggests a proper solvent for cleanup in their instructions. If you use the wrong solvent (in your case water), bad things happen.
i see. im not yet into this since at this time im working on water base inks.
thanks
Quote:
Originally Posted by RichardGreaves
Cleaning a water based ink with water but using a stencil with poor water resistance will damage the screen. You didn't tell us how you are exposing your stencil or what actual stencil you are using.
sorry again. im exposing using 150W floodlamp. sad to say, until now, i have no established time limit when burning screens. if you're referring stencil to emulsion, im using a bottled emulsion (no brand, violet color) with a separate sensitizer powder (orange).
If the stencil comes out of the mesh when you wash it - and pinholes appear, it didn't get enough exposure to UV-A light.
Incandescent lamps are not good emitters of UV energy. There is no reason to believe your 150W floodlamp produces much of any UV-A energy.
We can't advise you on exposure times for your unknown emulsion, but I would suspect that it is not very fast. Because you are adding a sensitizer, it 'could' be very water resistant.
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How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
usually with the emulsion im currently using and the time limit that ive set (10mins) using 150W flood lamp, it takes me a lot of time and water in washing out unnecessary emulsion in my design.
after exposure, i would go straight in the washing area with its lights off, then pour water in and out of the screen. after some time, i would start to use the pressurized hose. 5 mins isnt enough for me to get what i expect. i even scratch the design lightly to help in getting rid of the emulsion.
its been difficult for me. hope you could suggest an easier approach
usually with the emulsion im currently using and the time limit that ive set (10mins) using 150W flood lamp, it takes me a lot of time and water in washing out unnecessary emulsion in my design.
after exposure, i would go straight in the washing area with its lights off, then pour water in and out of the screen. after some time, i would start to use the pressurized hose. 5 mins isnt enough for me to get what i expect. i even scratch the design lightly to help in getting rid of the emulsion.
Stencils are easy. If it washes out, it wasn't exposed to enough UV-A light.
Unexposed stencil should wash out easily.
If it is hard to wash out, it was exposed to heat or UV energy and has started to cross link.
Test to see if your positive is blocking UV light. It some UV light leaks through the the positive, it can prevent the stencil from washing out in the image area.
The next time you expose, attach a coin to the stencil which will not let any light pass.
I would use a spray of water or a dip tank for washout. Regular water pressure will start to dissolve the unexposed stencil and rinse it down the drain.
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How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
If your using waterbased ink is your emulsion compatible with it? Do you degrease your screens before coating. I use to use waterbased ink and had to use an emulsion specific to it use. Therefore it was unaffected by water. I did have emulsion breakdown once around the edges of the image but that was when I had forgotten to degrease.
emulsion after washing out image 
