Trouble with washing out exposed screen please help, emulsion flaking off
I am new to screen printing, and coated a few screens and exposed them for quite a long time (20 mins) under my exposure unit, when i take it to the wash out i can see my design on the screen but when i wash the emulsion off bits round the edge of the design are flaking off
what am i doing wrong?
does it mean the screens are not dryed properly before i expose them?
Re: Trouble with washing out exposed screen please help, emulsion flaking off
Don't get disheartened. You are new. I knew nothing when I started, now people call me for advice. You'll learn as you go, there's just a lot to learn!
Anyway, your screens may have been greasy when you coated them, so the emulsion didn't stick well. Try a degreaser before you coat them.
It also might not have been dried properly, possibly dried only on the outside of the emulsion, not the inner part on the mesh. Try letting them dry longer.
Does your film/transparency have nice clean crisp lines of the design, or is it sort of fading? Nice sharp edges burn best.
How are you burning? did you build a unit? If so, what's it like?
Re: Trouble with washing out exposed screen please help, emulsion flaking off
20 mins is a long time, even if you're using a halogen bulb.
There are so many variables, so if you could post exactly what you are doing it would help nail down where the exact problem may be.
Stuart's advice was spot on, too.
1. Start with a fully-opaque film - you should see no light through the print on the film when you hold it up to a light.
2. You need to thoroughly degrease your screens before you coat them. Scrub them with a degreaser using a pad or brush that you only use for degreasing. Scrub both sides for several minutes, going in every direction, and make sure you rinse them very thoroughly. Then make sure they are 100% bone dry before you move on - put a fan on the screen and leave it for quite a while. Don't touch the mesh with your fingers at all once they have been degreased.
3. Coat both sides of the screen with emulsion using a scoop coater, and set the screen horizontally to dry. Again, put a fan on low to blow air across the screen as it dries. Best to let them sit for several hours, maybe more depending on the relative humidity where you live.
4. Make sure your film is held flat against the screen and can't move during exposure. Tape it in place with clear tape. What type of exposure unit are you using? What type of emulsion are you using?
5. Rinse out the stencil - wet both sides of the screen, wait 30 seconds, then spray out the stencil area spraying from the shirt side. A garden hose with a good spray nozzle works pretty good for most emulsions. If you're using a pressure washer, make sure you're not getting the nozzle right up close to the screen. The emulsion is a bit soft from the water, and can blow out with enough pressure even where there was exposure.
Again, it will help to know exactly what you're doing now and what products you're using, but definitely don't get discouraged... just keep learning!
Re: Trouble with washing out exposed screen please help, emulsion flaking off
Quote:
Originally Posted by brent
Don't get disheartened. You are new. I knew nothing when I started, now people call me for advice. You'll learn as you go, there's just a lot to learn!
Anyway, your screens may have been greasy when you coated them, so the emulsion didn't stick well. Try a degreaser before you coat them.
It also might not have been dried properly, possibly dried only on the outside of the emulsion, not the inner part on the mesh. Try letting them dry longer.
Does your film/transparency have nice clean crisp lines of the design, or is it sort of fading? Nice sharp edges burn best.
How are you burning? did you build a unit? If so, what's it like?
i managed to do a successful one lastnight, i had left the screens to dry longer and it helped lots, also from reading up on different threads i didnt realise the emulsion comes off where the design is more from the mixing of the water and the emulsion rather than the pressure of the water, so i took more time washin it out at a less pressure and seemed to work better.
Re: Trouble with washing out exposed screen please help, emulsion flaking off
Quote:
Originally Posted by Sheepsalt
20 mins is a long time, even if you're using a halogen bulb.
There are so many variables, so if you could post exactly what you are doing it would help nail down where the exact problem may be.
Stuart's advice was spot on, too.
1. Start with a fully-opaque film - you should see no light through the print on the film when you hold it up to a light.
2. You need to thoroughly degrease your screens before you coat them. Scrub them with a degreaser using a pad or brush that you only use for degreasing. Scrub both sides for several minutes, going in every direction, and make sure you rinse them very thoroughly. Then make sure they are 100% bone dry before you move on - put a fan on the screen and leave it for quite a while. Don't touch the mesh with your fingers at all once they have been degreased.
3. Coat both sides of the screen with emulsion using a scoop coater, and set the screen horizontally to dry. Again, put a fan on low to blow air across the screen as it dries. Best to let them sit for several hours, maybe more depending on the relative humidity where you live.
4. Make sure your film is held flat against the screen and can't move during exposure. Tape it in place with clear tape. What type of exposure unit are you using? What type of emulsion are you using?
5. Rinse out the stencil - wet both sides of the screen, wait 30 seconds, then spray out the stencil area spraying from the shirt side. A garden hose with a good spray nozzle works pretty good for most emulsions. If you're using a pressure washer, make sure you're not getting the nozzle right up close to the screen. The emulsion is a bit soft from the water, and can blow out with enough pressure even where there was exposure.
Again, it will help to know exactly what you're doing now and what products you're using, but definitely don't get discouraged... just keep learning!
thanks for the information, i didnt realise that degreasing the screen so much was so important
Re: Trouble with washing out exposed screen please help, emulsion flaking off
Looks like you've got a 1,000 watt halogen bulb for exposure - if you're using a dual-cure diazo type emulsion it shouldn't take more than 12 1/2 minutes. Shorter for higher mesh counts.
Re: Trouble with washing out exposed screen please help, emulsion flaking off
Quote:
Originally Posted by Sheepsalt
Looks like you've got a 1,000 watt halogen bulb for exposure - if you're using a dual-cure diazo type emulsion it shouldn't take more than 12 1/2 minutes. Shorter for higher mesh counts.
ah il try 12 minutes
iv done a couple of successful screens now with 18-20 mins
what happens if you over expose?
do you lose detail in the design?
my designs have been pretty plain so far
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Trouble with washing out exposed screen please help, emulsion flaking off 
