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  1. #1
    AlexG's Avatar
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    Liquid light and Screenprinting

    I've been wanting to get into screenprinting for a while. When you do this process, an image must be projected onto a screen that has a photo-sensitive emulsion on it to create the inking mask. After reading a few online manuals, it looks like the printers are using a Liquid Light type emulsion to put on the screen to create the masks.

    Anyways, Could I use liquid light to make the masks?...or do I have to go out and buy a special emulsion mix made specially for screenprinting?

    Does anyone have experience with any of this?

    Alex

  2. #2
    nick mulder's Avatar
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    Liquid light no, it will be too thin - special emulsion yes ...

    If you're interested in home brewing I think the process its most akin to would be Gum Bichromate.
    Cleared the bowel problem, working on the consonants...

  3. #3
    hrst's Avatar
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    In screen printing you use an emulsion that hardens in UV light. Then you contact print a very high-contrast film using a bright UV light. Then the mask is washed with strong water spray. Unhardened emulsion will loosen from the screen, leaving a positive mask.

  4. #4
    Ian Grant's Avatar
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    You can use an emulsion like Liquid Light for screen printing if you use the etch-bleach process. Back in the 70's when I dealt with Rockland Colloids they sold a specific enalarger speed emulsion for screen printing, Normally the screen is made of a dichromated gelatin or polymer layer that hardens with the action of UV light.

    I used the etch-bleach process commercially for a few years, it's great with RC papers, and also tried it with screen prints using the silver bromide emulsion my company manufactured, but we decided not to pursue screen printing.

    Ian

  5. #5
    Steve Smith's Avatar
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    Basic screen print emulsion is a PVA type glue with a bichromate sensitiser. We have a machine at work which coats both sides of the screens at the same time. For small scale work, a film such as Capillex would be more suitable.

    http://www.macdermidautotype.com/aut...tencil%20Films


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  6. #6
    Ian Grant's Avatar
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    Steve, it's not common now but there were Photo-emulsions made for screen printing by enlargement, I think they never really took off because most Screen print companies didn't have the equipment or skills need.

    You're right PVA/Bichromate emulsions tend to be used now but Gelatin/Bichromate used to work just as well.

    Ian

  7. #7
    Steve Smith's Avatar
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    Quote Originally Posted by Ian Grant View Post
    Steve, it's not common now but there were Photo-emulsions made for screen printing by enlargement
    I have never heard of those. Do you mean that the screen is positioned in place of the paper in an enlarger type of arrangement?

    This would be very tricky for us as we run to a print tolerance of +/-0.25mm and have to register prints to each other. Typically four for conductive circuits and around four to ten for graphic layers. We manufacturer flexible circuits, membrane switches and medical sensors on polyester substrate.

    http://www.parlex.com/products/ptf.php

    Stencil emulsion choice depends on the type of ink being used. Some emulsions can be removed with water and these are fine for solvent inks but we are increasingly moving over to UV cured inks which need a waterproof emulsion.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  8. #8
    Steve Smith's Avatar
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    Quote Originally Posted by AlexG View Post
    I've been wanting to get into screenprinting for a while. When you do this process, an image must be projected onto a screen that has a photo-sensitive emulsion on it to create the inking mask.
    To answer your original question, the usual method is to have the artwork on a film. Clear areas of the film will result in solid stencil and black areas of the film will result in washed out clear areas of the stencil. Therefore the artwork is a positive image.

    It is generally contact printed to the rear of the screen and exposed to ultra violet light. This hardens the areas where the light shines through and allows the areas which were covered by black (i.e. got no UV light) to be able to be washed out. This creates a stencil with clear areas to print the ink through.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  9. #9
    AlexG's Avatar
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    Yarrrrhhhhggg...


    I was hoping to just use stuff found at home, but now its looking like I have to go out and buy some special emulsion mix.

    Anyways Ian, could you shed more light on the etch-bleach process? Those chemicals don't look very hard to acquire and it might always be a possibility.

  10. #10
    Ian Grant's Avatar
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    Yes use under an enlarger with a high contrast line/lith negative. It was aimed at the art world rather than industry, I may still have a Rockland Colloids catalogue/price list from around 1976/7 in the UK with details of their commercial product.

    Your own field is more specialist and while+/-0.25mm sounds a tight tolerance it's nothing in comparison to photo-resists used for micro-chips.

    Ian

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