Im not sure what the symptoms are for overexposing so I will ask here. I am using a 110 mesh, 1 on 1 coat emulsion overnight in a darkroom. I burned the image with a 500 watt halogen, 16 inches away from image for 13 minutes. Took it outside and tried using regular home hose pressure but the image would not wash out at all. So I decided to use my pressure washer and washed out the image, and it started working! But than it went downhill from there, I have some detailed spots on my design and it started washing away! So i reclaimed that screen and coated a 110, 156, and 200 for tommorow morning. My question is, if the details wash off and almost look pixelated does that mean the mesh is too big and I should use a finer mesh? Perhaps a 200? During image wash out, are you supposed to be able to wash it out with regular hose pressure or a pressure washer (trying to determine if the screen was overexposed thus being difficult with normal pressure). And I hear different mesh counts have different burn times, the higher the mesh the less time it takes?, what the range for people using a 500watt halogen, for a 110 (guessing 11-13 mins), 156, and 200 yellow? Thanks guys!!
From what i understand, the distance your lights are suppose to be away from the screen is about 21 inches. While you were burning your screen did you notice if it was hot to the touch?
Another thing, after you burn your screen i wouldnt suggest taking outside as
the sun can keep exposing your image.
You should be able to use a regular garden hose to wash out your screen, i use that with a multi spray adapter on the shower setting.
It sounds like your over exposing the screen. Youo should be able to wash the screen out with a garden hose. You want to wet both sides of the screen then let sit for a minute or two. This will soften the emulsion and wash out will be easyer. I use the same exposer times for higher mesh counts unless they mesh is colored. If you have alot of detail in your design you might want to use a higher mesh count.
hi i have just made a screen with a 500watt ,the height of the light was 27 inches .burn time was 15 mins.i`ve done this for most of my screens with fine detailed designs and every time they have come out great.I use the shower with a medium pressure like someone said let it soften for a bit before giving it a good hose.I think it sounds as if your using to much pressure with the jet.
You can not take a screen out side to wash it out. The sun is nothing but UV light...what causes the emulsion to harden. One split second of sun light can be more than an hour of light under a 500 watt bulb. If you have to take it outside, get a spray bottle full of water and soak the screen down until the image is washing out.
Then take it outside because the soaked emulsion will not setup all that fast. You will also be able to use very little pressure to wash it out saving your screen pressure damage.
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__________________ At the edge of our dreams lay the ideals of true creation.
Im not sure what the symptoms are for overexposing so I will ask here.
If fine lines close up and ink won't transfer through them, you have over exposed that particular stencil. Another stencil could do fine. Dual-cure emulsions are the best for detail, but slower than SBQ stencils. Your 500 halogen lamp is near the bottom of the UV light food chain. I suggest that you will be happier with the excellent fine line and halftone results you will get from an SBQ emulsion, that will work better with your 500 watt halogen lamp.
If you need finer detail that you can get with a dual-cure, you should pair it with a stronger lamp or you won't see bette results. A dual-cure with your lamp is like racing tires on an old station wagon. It works, but it's not the hot setup.
Quote:
Originally Posted by TeddyRocky
I am using a 110 mesh, 1 on 1 coat emulsion overnight in a darkroom. I burned the image with a 500 watt halogen, 16 inches away from image for 13 minutes. Took it outside and tried using regular home hose pressure but the image would not wash out at all.
Washing outside is not recommended because of the sun.
110 is not a fine detail mesh.
16 inches would be OK for a 10 inch image.
How did you measure your exposure?
Quote:
Originally Posted by TeddyRocky
So I decided to use my pressure washer and washed out the image, and it started working! But than it went downhill from there, I have some detailed spots on my design and it started washing away!
Unexposed stencil has to dissolve. Many impatient screen makers want to use more power and that can damage the sensitive stencil.
If I wanted to dissolve sugar cubes, would they dissolve faster if I sprayed them with a garden hose for 5 minutes?
Make an experiment for me. Make a very small coat on a screen and let it dry. Now wash it out, don't expose it, just wash it out. That is your standard time for washout.
If you have areas of the screen that are hard to budge, you know they were crosslinked somehow. Heat or UV can do that.
If you have areas that are hard to washout, your positive probably failed you. UV got through the positive and exposed the stencil, crosslinking it.
Properly exposed, a stencil can stand up to spray from a pressure washer, but remember, Hydro-Blaster showed the world 20 years ago that you can punch a used stencil out of mesh with 1,500 to 3,000 psi water pressure and NO chemicals.
Quote:
Originally Posted by TeddyRocky
So i reclaimed that screen and coated a 110, 156, and 200 for tommorow morning. My question is, if the details wash off and almost look pixelated does that mean the mesh is too big and I should use a finer mesh? Perhaps a 200?
Without knowing how thick your lines are, nobody can tell you which mesh. What is your finest line? A line should be supported by three threads.
Go into your illustration program and make a positve with .005", .010", etc. lines. Use this as a test pattern and measuring comparitor. Copy this image to EVERY image you make as a constant test.
Quote:
Originally Posted by TeddyRocky
I hear different mesh counts have different burn times, the higher the mesh the less time it takes?, what the range for people using a 500watt halogen, for a 110 (guessing 11-13 mins), 156, and 200 yellow?
Different thicknesses of mesh means different thicknesses of stencil and different exposure time. Thicker stencil is harder for the UV light to penetrate. Different thicknesses of steak, means different time of exposure to the heat on the grill.
Dyed mesh absorbs uncontroled UV light bouncing and reflecting around the inside of the stencil that can close up an opening, BUT you also have to expose for longer.
__________________
How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
Last edited by RichardGreaves; April 16th, 2007 at 02:05 PM.
Greaves...what do you do for a living? It seems like you write for a printing rag because you detail what you write with accurate and very knowledgable facts.
Good to have you around.
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__________________ At the edge of our dreams lay the ideals of true creation.
Greaves...what do you do for a living? It seems like you write for a printing rag because you detail what you write with accurate and very knowledgable facts..
I've had a 'real' job as Product Manager for Ulano for the last 2 years. I wrote a monthly column in Screen Printing magazine for 9 years called "Greaves On Garments". I was the Technical Editor for Printwear Magazine from 1995 to 2000. For the last 7 years I have been the only speaker about screen printing at the 5 Printwear shows each year. I am the Librarian and active member of the Academy of Screen Printing Technology.
And when the job has to get done, I've been know to allow washing out screens outside with a garden hose.
You are not alone, but it's a bad idea
Nassau December 2002 -Saxons Club
__________________
How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
Last edited by RichardGreaves; April 16th, 2007 at 02:02 PM.
Thanks guys...I sucessfully made 3 perfect screens today; a 110, 156, and 200 mesh. They all did great and I test printed them for fun and just noticed that the 200 is hard to press ink through to the shirt, so I had to pull 3 times for the ink to flow onto the shirt. Next step is to do a 4 color print.
.... just noticed that the 200 is hard to press ink through to the shirt, so I had to pull 3 times for the ink to flow onto the shirt.
You will find that when you make screens with higher tension and use stiffer squeegees, the ink has no choice - and stays on the surface of the shirt. Higher tension, higher mesh counts, lower off-contact and faster squeegee stroke is the goal of your printing.
Do an experiment. Print that 200 mesh screen on a piece of paper. You will see that it prints a smooth flat print, which is why a transfer is the best print for dark shirts because it's not effected by the open areas or holes of a shirt.
The mesh of a 200 is also metering the amount of ink deposited
__________________
How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
Overexposed? High pressure? 
