[Nature Isle]

I am new to screen printing and can't get started. I have Saatichem textil DW emulsion. It was delivered 10 days ago and I mixed the sensitizer less than a week ago. The violet emuslion immediately went a brownish color. When I apply it to a screen and dry, it doesn't wash out, even with no exposure. Questions -
1. could it have got too warm and been ruined (I'm in the Caribbean)
2. I have a primitive set-up and some daylight does get in - I don't have a dark room. Is ambient light enough to fix the emulsion.
3. Is there something else I am not thinking of?
Thanks

 

[sben763]

I would say that it is possible that a combination of heat and the light have ruined the emulsion. Did you mix the sensitizer with bottled water or tap.

 

[Nature Isle]

Tap water
Oh crap - was it that simple, I ruined it with tap water?

 

[sben763]

Tap water
Oh crap - was it that simple, I ruined it with tap water?

It is probable. You said you live in the carrabeain and depending on the contaminates that come with municipal water or even well water. Here in the States if people only new of the possible contaminates in the water. I be seen in some places where I lived where you can get a chlorine reading from the tap about .5 ppm from a pool test kit and although it would only last for a day I Belive chlorine will ruin diazio.

 

[Nature Isle]

I'm guessing I'll start over
many thanks for replying
Andy

 

[BroJames]

you can leave the water overnight and that should solve the chlorine problem but other contaminants are a problem as well. I use bottled distilled drinking water for whatever I need to mix with water.

If you must work outside a dark room, avoid even indirect sunlight if possible. Work in a dark area or try coating at night with a bulb just enough to barely see what you are doing. You don't need to move fast but go about without wasting time.

Change of color with an accompanying unpleasant smell would indicate that the emulsion is going bad. But that would usually result in a wash out. A failure to wash out suggest premature exposure. Where did you dry your coated screen?

 

[sben763]

I'll add that a incadesant light puts out very little UV light and diazo emulsion isnt as sensitive when wet so coat at night with a incadesant bulb or yellow coated bug light(not a floresant yellow party light) dry at night and if you need to, store in a black plastic trash bag. I did this and stored them for 7-21 days without any issues. Then expose. if your using the sun to expose it only takes a few seconds especially that close to the equator so washing out outdoors during daylight hours will not work

 

[Nature Isle]

Thank you Angel. the technical note that bad emulsion would wash out makes me think. Maybe the screen is just getting too much light. I'll try again at night. I may try to create a dark room. This forum is a life-line, I was about to give up! Sincere thanks for replying.... Andy

 

[Nature Isle]

I'll add that a incadesant light puts out very little UV light and diazo emulsion isnt as sensitive when wet so coat at night with a incadesant bulb or yellow coated bug light(not a floresant yellow party light) dry at night and if you need to, store in a black plastic trash bag. I did this and stored them for 7-21 days without any issues. Then expose. if your using the sun to expose it only takes a few seconds especially that close to the equator so washing out outdoors during daylight hours will not work

I am using sunlight and I am washing out outdoors. I may be approaching this with a bit less precision than needed! So, dark room or night, store in pitch black, expose carefully, wash out in low light - got it. I have been careful and I have done all this before in a workshop, I think I was just assuming it was easy when actually a great deal more care is needed. Many thanks for your replies - looking forward to getting this right.

 

[BnC Custom Ink]

I believe it is iron in tap water that reacts with the diazo/emulsion, which might explain the brown color. Use only distilled bottled water, not drinking bottled water. Or switch to a photopolymer emulsion.

Sent from my PC36100 using T-Shirt Forums

 

[TYGERON]

I am new to screen printing and can't get started. Is ambient light enough to fix the emulsion.
3. Is there something else I am not thinking of?
Thanks

Andy. There could be any of many causes for what's happening. The violet to brown color change may just be from the sensitizer. Mine starts blue then turns green beause the sensitizer is yellowish. Add yellow to violet and you (may) get a brownish hue. I'd venture to guess it's a light/UV exposure issue. Doesn't take much pure UV to fix an emulsion.

As far as being a beginner, there's quite a bit to know to minimize issues that an keep you from the fun part. My suggestion would be to get a comprehensive screen printing instruction DVD or book and watch/read it all the way through a couple times. until you have a more comfortable understanding of the whole process and how everything goes together. A lot of issues you may have may be solved before they arise.

 

[TCT]

I would agree with TYGERON, it has to do with the light coming in. A little bit of light over a long period of time can definitely expose the screen. I would put my money on this.
You could always try a simple elimination, leave the water you mix in the emulation out over night, then mix it it. That should take care of any problems from the emulsion side.

 

[BroJames]

I believe it is iron in tap water that reacts with the diazo/emulsion, which might explain the brown color. Use only distilled bottled water, not drinking bottled water. Or switch to a photopolymer emulsion.

Sent from my PC36100 using T-Shirt Forums

This is a bit of OT but I drink the excess bottled distilled drinking water so maybe it is also of interest to others.

I do not drink distilled water as a matter of practice but I started drinking "branded" bottled distilled water when I first started using it for diluting emulsions. A practice I do not do now. However, I still add/spray distilled drinking water to waterbased inks from time to time and drink the excess distilled water.

The "branded" distilled water are bottled by big companies and as I understand the process involved, distilled water is highly purified water with all or almost all of the impurities including minerals removed through distillation. So it contains no impurities and minerals and the reason I do not drink it as a matter of practice is because of some claim (or joke?) that prolonged drinking of distilled water is not healthy because it contains nothing but the purified water.

So what is the difference of bottled distilled water and bottled distilled "drinking" water? Or, why can't or why shouldn't one add distilled "drinking" water to the emulsion?

 

[Nature Isle]

A reply to all who have helped - THANK YOU
By moving dramatically from careless impatience to concentrated structure and care, I produced a great screen. My suprise was the timing, I did a test screen revealing an inch every 10 seconds and got the best result at just 30 seconds. Thanks go to sben, I thought it would be minutes, and I even read an article that instructed you to leave the screen exposed to the sun for 20 minutes! My shower head set on power jet is perfect for washing out and dark too. So I have the full process mapped out now, thanks to your help.
Next I just have to find some t-shirts...

 

[TYGERON]

...I even read an article that instructed you to leave the screen exposed to the sun for 20 minutes! My shower head set on power jet is perfect for washing out...

Yes I came across that misinformation too. I think it meant "seconds" instead of minutes. One reason not to believe everything on the 'net...LOL!

Don't know how hard your shower head sprays but if an emulsion is optimally cured, not much pressure is needed even for fine detail. And if it is a bit underexposed it can blow out with too much pressure. Also know that you'll have different exposure times as your light source ages and also with different mesh counts and mesh colors. Use an exposure calculator to get accurate times.

 

[wBranco]

hello

i also use textile dw emulsion.
i live in canada and i also mixed the yellow powder with tap water.
but i've seen people do that and works perfectly.

i use a speedball remover(diazo) and for me it doesnt work at all.
this remover works miracles with its own brand speedball emulsion diazo. but i asked and they said it was compatible.

i used bleach and it did amazing at removing most of the emulsion. now the screen has a hazy pinkish colour. its not as clear as..well a reclaimed screen but you can see my hand through it ( in a haze).

my emulsion was purple and now its brown (i was scared but it made sense when i thought of the mixing colours) the first one i did came out good although it was underexposed. and every try after that has been underexposed and with out luck of reclaiming my screen.
in the las try i tried exposing it with the sun even if it wasnt reclaaimed to see what happens when its "perfectly exposed" well it turns back to purple OR looks more purple then the brown you start with
when i saw that after i read a forum that it stated that your emulsion when fully exposed will change back to its normal colour when fully exposed i just died because it was a good news after many hopeless news .

i washed it out with bleach and it did better at it then before. :O another smile to my face
i guess its because its water-resistant and when its underexposed its even tougher to get out :S

now i have a very light haze..as i said before its ligh pinkish and you can see things in a haze.
buti tried putting ink through (with a Squeegee) and it only pases through some little parts that are fully emulsion free.

what can i do???? help please!! btw i have no money :S i know this is going to sound cheap and maybe unacceptable to some but please help me with easy solutions or substitutions if theres none its ok :'( haha


BTW: in my last try, when my emulsion turned more purple, i used the sun and it was a cloudy day (100%) and i stay there doing calculations and noticed how the emulsion started changing purplish after ten minutes