I don't know what's up. I needed to burn two images for band tshirts. One worked, the other didn't (and hasn't the additional two times I tried). Same preparation + burning process. Why would one work and not the other? Both images printed black on transparency, both burned for the 20 minutes I typically use (500 watt halogen bulb), but one wouldn't wash out. Any suggestions? Any chance the transparency image could somehow not be dark enough? It looks black, is black, but maybe not super-duper black?
What emulsion are you using? 20 minutes is pretty long, even for a 500W halogen.
Did you print both the positives with the same settings? Should use heavyweight matte or similar setting to lay as much ink as possible.
Are both transparencies the same?
Does the one that doesnt work have more fine lines than the other?
hmmm... not sure of the emulsion. I transferred it to a cleaned ketchup bottle a while back for easier application.
The 500 watt halogen is placed about 2 feet from the screen; maybe a little less.
Both images were created in photoshop... transparencies look similar in tone (different images).
The one that doesn't work actually has fewer fine lines--the non-working one is text; the other is a line-filled image of trees.
weird, really. I can't figure out what's going on.
The screens are over exposed; either a positive that is not dense enough or too long an exposure time. 20 minutes does sound too long. Have you burned other screens previous to this job that washed out ok using the same setup? - Scotty
-Double your transparancies if you don't already to create a darker image. Perhaps even use three transparencies depending on your printer.
-Play with your exposure time. Overexposing can be the same if not worse than underexposing. You must really test out for perfect exposer times based on your setup. This will change based on your stencil thickness, type of emulsion, exposure setup and so on.
-Make sure your design is not getting exposed between your light source and washout boothe / method. Simply fix this by putting your screen in a black garbage bag when transporting it from room to room or under any kind of light.
-Do you have a sheet of glass on top of your screen to make sure that your transparancy is laying flat on your screen and no light is seeping beneath?
Try to pinpoint what went wrong between the two screens for you, and where to start fixing your problems since there are so many variables that can effect your exposure.
I have a similar set up 500w halogen, 18 inches away, qtx emulsion, burn for 8 minutes.
I've had no problems with this set up for the last year or so, but recently the emulsion is starting to peel off around the edges when I wash the screen out. so frustrating!
any thoughts on what the variable could be? the only thing I can think of that changed was that my workspace (the basement) is really cold right now! that and I've been reclaiming/reburning kind of quickly and maybe I'm not letting the emulsion dry enough before burning.
perhaps the emultion on some of your screens might have become exposed by accident? Can you see a design trying to wash out, but wont? If your dark room is not white light safe they can be exposing just sitting there. Some emultions expose very quickly and need to be in a light safe area until you need to expose your scree. Also if your screens have been coated for a long time they may need to be stripped and re coated for a fresh screen! good luck
i just want to throw this in,...you are using a scoopcoater? maybe each screen has a thicker deposit of emulsion and therefore will affect the burn time.
#1 Dont transfer your emulsion to another clear container from the black plastic bucket. It is black for a reason. The reason being that the emulsion inside is sensitive to any white light.
#2 Perhaps light got to the second screen before you tried to expose the image.
#3 Expose an image at various times times to find out what the idea exposure time is for that particular emulsion applied at that particular thickness. The thicker the emulsion the longer you need to expose all the way through it.
You've already identified two varaibles, the cold and screen drying time, that you must eliminate to go on to solve your problem. Also take into consideration that all lamps lose significant output during their life; it may be time for a new lamp (bulb). - Scotty
how much does the thickness of the emulsion affect the exposure time?
the thicker the emulsion the longer it will take the uv to completely penetrate and expose the screen...thats why a 110 mesh screen takes longer to expose than a 305 ...because the is a thicker deposit of emulsion on a 110 than there is on a 305......
the thicker the emulsion the longer it will take the uv to completely penetrate and expose the screen...thats why a 110 mesh screen takes longer to expose than a 305 ...because the is a thicker deposit of emulsion on a 110 than there is on a 305......
Inked
This does depend on coating technique. If you use the same technique, it is true that less emulsion will end up on a 305 than a 110, but this isn't necessarily desirable. I always make sure to coat screens with a uniform stencil thickness to achieve an opaque print on the garment. I've heard people say that they coat thinner screens for halftone work, but I find to be able to lay down enough ink in one pass, a thick stencil is required regardless.
It's also important to note that most high mesh screens will come yellow or orange instead of white and that this will take usually around 50% longer to expose.
frustrated with exposure, please help 
