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Hi guys, Sorry if this has been asked but I'm having some dramas! Last night i coated two brand new screens fresh from the wrapper. I coated them with Murakami photocure TXR (pink) and left them to dry over night with a fan. Normally they are touch dry in about 15mins but i leave them longer anyway. My exposure unit is 6x15watt blacklights (a bought unit) and exposed my screens for just over 1 min. Can't really find any info on exposing this type of emulsion with blacklights, their site says 20-40 secs with a 500kw metal halide. Anyway, after the burn is done i lightly rinse my screens to see the stencil (as you do!). Everything looks good and very sharp. All my detail is still there....As soon as i apply a bit more pressure it's time to say bye bye to the stencil because it just keeps getting washed out! So. Can one shed some light on this matter? Is it a case of me needing to burn it for longer? The longest burn I've done is about 20mins and took about the same time to wash out, stencil and all! PLEASE HELP

Ben
peace!
 

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I don't have any experience with the stuff your using, but that's long enough in many cases.
Depending on how dark the room you store it in is etc.
Mine usually lasts longer, but I've seen stranger things happen
 

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I don't have any experience with the stuff your using, but that's long enough in many cases.
Depending on how dark the room you store it in is etc.
Mine usually lasts longer, but I've seen stranger things happen
Its kept in my storage unit (no light in there). Being a rather new bottle, I'm a little lost. I don't want to keep using other people to do it when I know I can do it myself...it's worked in the past for me just not now! Hmmm
 

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Your screens are either underexposed or your emulsion is no good. The three factors are light source, exposure time and emulsion. In this case the positive can be ruled out since even the non blocked out areas are being washed out. Since even a 20 minute exposure is being unsuccessful, I would tend to think that exposure time is not the problem. So it comes down to light source and emulsion. I'd suggest using a known good uv light source, the sun, to test the emulsion. Exposure using the sun is very quick (around 45 seconds for me). You mentioned that these screens are 'fresh out of the wrapper'. It is possible, but unlikely, that the screens are contaminated and not allowing the emulsion to lock to the screen.

Personally, I don't understand why screen printers use a dual cure emulsion unless it is for high end prints. Pure photopolymer emulsions work every bit as good as the dual cures but also eliminate the mixing and have a much longer shelf life.

- Scotty
 

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Ben,

Have you tried coating another set of screens using the same emulsion? If you experience the same problem, then you know the problem lies with the emulsion, if not, then probably the screens.

Did you just pull the new screens out and start coating them? I normally wash new screens out and degrease them before using. I've heard you should use an abrader anytime you break in a new screen.
 

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Scotty, I've never considered a type other than dual cure. What else would the pure photopolymer be called? pre-sensitized? I'm just looking on the Ulano site.. Pre-Sensitized Emulsions for Screen Making Products

You said 'unless it is for high end prints'. What types of prints are considered high end? IE what can't I do with the pure photopolymer stuff?

I've read some posts from some screenprinters claiming that the dual cure does a better job capturing the dots of high end process color jobs using mesh counts of 305 and above. Other than for that purpose a pure photopoymer emulsion is fine to use. My highest count mesh is 230 and halftones or very fine detail is no ploblem.

I'm not sure if the terms pure photopolymer and presensitzed can be used interchangably in all cases but it's generally accepted that they are the same.

- Scotty
 

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Have you spoken to the supplier?

Hi guys, Sorry if this has been asked but I'm having some dramas! Last night i coated two brand new screens fresh from the wrapper. I coated them with Murakami photocure TXR (pink) and left them to dry over night with a fan. Normally they are touch dry in about 15mins but i leave them longer anyway. My exposure unit is 6x15watt blacklights (a bought unit) and exposed my screens for just over 1 min. Can't really find any info on exposing this type of emulsion with blacklights, their site says 20-40 secs with a 500kw metal halide. Anyway, after the burn is done i lightly rinse my screens to see the stencil (as you do!). Everything looks good and very sharp. All my detail is still there....As soon as i apply a bit more pressure it's time to say bye bye to the stencil because it just keeps getting washed out! So. Can one shed some light on this matter? Is it a case of me needing to burn it for longer? The longest burn I've done is about 20mins and took about the same time to wash out, stencil and all! PLEASE HELP

Ben
peace!
 
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