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Letting emulsion "dry" before exposure...

20K views 23 replies 12 participants last post by  VBGrafx 
#1 ·
Went to Blick and picked up some QTX emulsion to try out tonight. My question is:

After I have applied my emulsion to my screens, how long do they have to sit before I can expose them?

Note-They will be concealed in a cardboard box to keep out of the light and not in the open with a fan or anything.
 
#2 ·
It really depends. How is the humidity where you live? If it is high, there will be a lot of moisture in the air and it will take longer to dry.

To be safe, I would say let the screens dry over night. Putting them in a dark closet (free of dust) with a dehumidifier will also speed up the process.
 
#3 ·
hmmm...ok. I don't wanna take any chances with a dusty closet so I'm gonna stick to my big cardboard box scenario.
But I'm guessing that..leaving it overnight to dry means- maybe I should wait 12 hours or so? Usually I have been letting it dry for about 24 hours just to e on the safe side but I was hoping somebody might say "You only have to wait five hours!" or something haha so I can jump on it!
Oh well...Thanks!
 
#6 ·
You can touch the outer edges of the emulsion to check how long it will take before it dries. You can overcoat a little for this purpose if needed. The time really varies on the temperature and humidity. I thought it is hot here but having read how hot New Jersey is, and how Eli's screens dry in less than an hour in Texas, the time really varies.

As JSF posted, you can try a hair dryer to hasten the drying. You can also use an electric fan.
 
#7 ·
It gets really humid this time of year in St. Louis. Here is our process for drying...
We use a light safe garage :D and wait until dark. After the emulsion is done, we set each screen facing down in a closet. The screens are spaced with caps from small bottles. We wait a good 12 hours to be safe and it works every time. The quickest time I've achieved in drying is 2 hours.
 
#12 ·
So- If I'm correct, y'all are saying it's better to live in a warm and humid area and yet keep the air flowing?

My house is pretty cool...california bay area weather...doesn't go above or below 65-70 degrees usually haha.
But I have no garage and I'm afraid my warehouse is a bit dusty to be putting my screens in a room with a fan blowing around.
 
#14 ·
We stick them in the (broke) drying cabinet in the dark room, leave the door on tht cabinet open, and put a fan pionting to the cabinet. So it is more of a rack instead of a cabinet. It takes about an hour to dry. I would suggest that you not stand them up, but have the face upside down so the emulsion drys evenly. Don't put the emulsion on too thick. Quick pass on both sides should do it. The "Louisiana" dark room is Hot as Hell and Humid too. The heat will expose the screens too, so I wouldn't coat too many screens until you need them.
 
#19 ·
Yes, you can use heat but most emulsions degrade at heat over 90f. Air flow is the key to quick drying. You will run into reclaiming issues if you use the screens before they are completely dry thru and thru. Shouldnt take more than a couple hours unless it's raining outside or extremely humid.

Best of luck.
 
#23 ·
Raining! Did someone say Raining.... I live in South Louisiana.... Raining is our specialty! And don't mention humidity.... Our drying room is HOT and HUMID. But seriously, we just run the fan towards the screens as they dry in the rack. about 1 - 2 hours and they are ready to roll....
I though that is the specialty of seattle.

Is your rack open on all sides?
 
#21 · (Edited)
I have always use 100F as the "critical" temperature. Not only is it easier to remember but I read somewhere that 100F is still a safe temperature. I think it is above 105F that is not good for the emulsion. I forgot where I read the article and am not sure if it applies to all types of emulsion.

However, I have dried screens using hair dryer and even a heat gun and have no problems reclaiming screens. Specifically, I have a fan blowing at layers of screens with 1" spacing in between them(to circulate the air). I direct the blower towards the front of the fan to create warm but not hot air. With a heat gun, you have to move it more quickly otherwise it is not good for the emulsion. Not sure what the temperature on the emulsion is though.

My first screens were dried only with a hair dryer and no fan but you have to move the hair dryer continuously. I do not have problems reclaiming if we are to use it as basis to determine if the screen received too much heat or not. I think it is the prolonged high heat that is damaging.

I would think that a dehumidifier is best because by lowering the humidity less heat is required to pull out the 70-80% water in the emulsion.

Edit: Just did a little googling and found on Chromaline's site:
Ideal drying temp is 110F
70F 50% humidity typical drying time is 1 hours
100F 20% humidity typical drying time is 15-20 minutes

Source: http://www.chromaline.com/technical_articles/ta_howtodry.pdf
 
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