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screen printing => Screen Making => Topic started by: Jhtitan on April 18, 2019, 04:30:16 PM

Title: Screen prep problem
Post by: Jhtitan on April 18, 2019, 04:30:16 PM
So we are just starting out so this was my 3rd set of prepped screens. What would cause this? the emulsion seems to have ran and dripped. This was the top of 3 screens and all under this were ruined as well.

I read someone here say 1/1, which I am guessing is 1 pass on outside then one on the inside, I have been doing 1/1/1, three pass, start and finish on the inside. Worked great on the first 12 screens. these last 4 I did I had 1 good screen and then this screen and the 2 under it all looked like this. I am using only plastisol ink at the moment, we got close to 400 gallons with the equipment so we are not planning on using anything else just yet.

I had seen some beading on the edge of one or 2 of the previous screens but nothing like this.

Also the first 12 I did all but the last 4 seemed to wash out pretty easy. Then the last 2 of those and the one good from this last batch took forever to wash out. They took so long actually that I reburned 2 screens thinking the screens had somehow gotten exposed before hand. I have them in a light tight frame rack I built under the exposure unit.

Any suggestions or thoughts are appreciated. I need to wash these 3 out and try again. I will try 1/1 on these 3 and see if I am just over coating them.

Thanks
Jon
Title: Re: Screen prep problem
Post by: aauusa on April 18, 2019, 04:42:27 PM
to much emulsion on the screen.  it dripped off on to the others.      some may say loose screen but it looks like they are tight in the pic.

many other will chime in but here is my .02 help on coating by hand

I use a glisten method,  meaning I coat on the shirt side until i see the emulsion start to glisten on the ink side of the screen.  when I see this I do 1 coat on the ink side, and done.  It make take 2,3,4 coats to get a glisten just depends on the pressure you are using and the black of your coater(round or sharp) edges and which side you are using.   I use the sharp edge. 

But I would increase your pressure on the screen when coating and this will help eliminate this issue regardless of how you decide to coat.   and when done right the emulsion is one shade through-out the screen.   you see on yours where the emulsion is light(thinner) in some areas.   

you can always over coat and then do a hard scrape to get excess off as well.   
Title: Re: Screen prep problem
Post by: 3Deep on April 18, 2019, 05:00:33 PM
Are you using the sharp edge of the coater or round edge? and yes are the screen tight, loose screen mesh will cause that to happen every time.  what mesh screens are you coating anything below 110 might drip and do you use any type of air to help dry the screen.  The higher you stack a thick coated screen gravity will take over unless you have a fan or dryer blowing on them.
Title: Re: Screen prep problem
Post by: RICK STEFANICK on April 18, 2019, 05:03:59 PM
did you use a scoop coater?
Title: Re: Screen prep problem
Post by: Maxie on April 19, 2019, 04:57:35 AM
Make sure you are using a coater.
Start off with 1/1 using the thin side. (You can increase thickness later)
Dry the screen flat, shirt side down. (It looks like you dried the screen standing up.
Looks like you have way too much emulsion and are not drying level.
Title: Re: Screen prep problem
Post by: BP on April 19, 2019, 07:21:19 AM
Jon, I really think you would be better off by paying someone to come to shop and teach you the craft of screen printing. All of these printing 101 problems will go away!
Title: Re: Screen prep problem
Post by: Jhtitan on April 19, 2019, 08:26:40 AM
Thanks all for the input.

So far we have stuck to the 150 -200 mesh screens. all screens are tight, at least they seem tight. I don't have a way to measure how tight they are.

I am using a scoop coater, I am not sure if I am using the sharp or round side honestly. I am using the side the previous owner had marked as "Use this side" with sharpie. I will check tonight and see if I can tell a difference.

I am drying them flat with the shirt side down. While my floor may not be completely level, it is a basement floor, they should at least be somewhere close level. I built a storage cabinet under the exposure unit. The cabinet was wrapped on 5 sides with black waterproof coated canvas. Ir is UV resistant and light tight. The doors are 2 flaps of the same with velcro around the edges. I am concerned with airflow. My next plan is to get a fan added to one side with some duct work and then an exhaust duct on the other side.

I have been doing 3 coats, ink side/ shirt side/ ink side. And the screens did not look like that when they went into the cabinet. they were clean with almost no streaks or lighter coated areas.

I will try 1/1 and see how that works out and I will also try to get some airflow into the cabinet, I may have gone a little overboard on making sure it was light tight and made it too air tight in the process.
Title: Re: Screen prep problem
Post by: dsh on April 19, 2019, 09:16:07 AM
My granddaughter came for a visit and wanted to coat a couple screens.  The same thing happened.  I figured it was a lack of wrist strength and she didn't put enough pressure on the screen with the coater.  I'd say use the sharp side of the coater.  I've gotten the same kind of effect when using the wide side.
Title: Re: Screen prep problem
Post by: inkman996 on April 19, 2019, 09:17:45 AM
Is their high humidity in the room? If the emulsion does not start drying fast enough it will start to run like in the pictures. Moving air is really important to get them to start to dry, our screens have two fans pointed at them while drying.
Title: Re: Screen prep problem
Post by: whitewater on April 19, 2019, 09:56:36 AM
seems no air flow in your cabinet and high humidity. I bet if you coat the screens and the leave the door open to the box and blow a fan in there it will help.. also being in the basement higher humidity, get a dehumidifier .  I know because I started in my basement 15 years ago.
Title: Re: Screen prep problem
Post by: Prince Art on April 19, 2019, 10:01:24 AM

The difference between sharp and round side of the scoop coater can be massive. I've always used the sharp side; tried the round not long ago to experiment, and I had emulsion dripping & running everywhere.

If you're still getting too much emulsion, you could try coating 1 outside / 1 inside / scrape outside / scrape inside. (Medium pressure on the scrape.) Not most people's standard practice, but it's worked for me with high-solids photopolymer emulsion.
Title: Re: Screen prep problem
Post by: Frog on April 19, 2019, 10:31:21 AM
Jhtitan, the first response to your post here mentioned the use of the "Glisten" method.
When coating a screen. for use with plastisol inks, this method all but eliminates many of the other variables.
Tried and true, check it out here http://www.theshirtboard.com/index.php/topic,2621.0.html (http://www.theshirtboard.com/index.php/topic,2621.0.html)
Title: Re: Screen prep problem
Post by: Frog on April 19, 2019, 11:05:46 AM
The next issue that folks brought up here was the drying of the coated screens. Doug and his (our) friend John have you covered on that as well. https://www.vastex.com/Articles/Screen-Drying.php (https://www.vastex.com/Articles/Screen-Drying.php)
Title: Re: Screen prep problem
Post by: Jhtitan on April 19, 2019, 01:10:09 PM
I ordered some fans to add to the bottom of my cabinet along with some exhaust venting near the top should fix the lack of airflow problem. I do know the second round I prepped we were trying to speed the drying time so I had opened one side a bit and set a fan pointed in along with a small gap on the other door to let the air out again. I am now thinking it may have been the lack of air flow mostly coupled with a bit too much on the screens. I will see how this works and let you know what I find.

I will look at adding a humidifier in there as well.

Not sure if it matters or not but we are using Chroma Blue emulsion.

Do the scoop coaters wear out at all? Other than damage from drops and such I mean.

We are going to see if a friend that is in the business can come over and take a look at everything for us. Just to make sure we are doing things the best way possible.

As always you guys are a great help!

Jon
Title: Re: Screen prep problem
Post by: Frog on April 19, 2019, 01:44:45 PM
I ordered some fans to add to the bottom of my cabinet along with some exhaust venting near the top should fix the lack of airflow problem.
Jon

Consider adding some filter material to the intake fans (and monitor its condition)
Otherwise, you are essentially making the cabinet itself act like the canister of a vacuum cleaner.
Title: Re: Screen prep problem
Post by: mooseman on April 21, 2019, 10:32:17 AM
Just my 2 cents
mooseman
Title: Re: Screen prep problem
Post by: RICK STEFANICK on April 21, 2019, 04:55:15 PM
OK.. WOW.. All you need to do is coat the screen properly with the correct pressure and a sharp edge scoop coater. dry print side down vertically. Done ..
Title: Re: Screen prep problem
Post by: Jhtitan on April 22, 2019, 10:08:30 AM
Thanks Mooseman, I really didn't even notice the edge where it looks like the emulsion looks to have beaded off the screen. I did power spray , degrease, rinse, and dry overnight. You may be correct tho that I did not get it rinsed well enough. I will add that to my check list and make sure it is clean and well rinsed. The 2 screens below this one were ruined as well but I believe it was all due to this screen dripping on the one below, the whole crap rolls downhill scenario.


Thanks again everyone!

Jon
Title: Re: Screen prep problem
Post by: RICK STEFANICK on April 22, 2019, 05:07:30 PM
Thanks Mooseman, I really didn't even notice the edge where it looks like the emulsion looks to have beaded off the screen. I did power spray , degrease, rinse, and dry overnight. You may be correct tho that I did not get it rinsed well enough. I will add that to my check list and make sure it is clean and well rinsed. The 2 screens below this one were ruined as well but I believe it was all due to this screen dripping on the one below, the whole crap rolls downhill scenario.


Thanks again everyone!

Jon

ok  . THATT ISN'T RINSING MY FRIEND AND YOUR COAT WAS TOO HEAVY!!
Title: Re: Screen prep problem
Post by: Atownsend on April 22, 2019, 08:30:55 PM
A dehumidifier in the dark room / space goes a loooooong way. Coat thinner, or dry quicker. Have seen this before but it’s been many years & I can’t recall the crapstorm of variables.
Title: Re: Screen prep problem
Post by: mooseman on April 23, 2019, 08:19:50 PM
One problem with a situation such as this is sometimes you solve the problem but don't understand what made the difference.
I can't hold a candle to Rick's experience but offer the following journey to a solution...
you mention the problem on 3 screens so take one and process it exactly the same as you always do
take the next and clean it very well... even wipe it done with alcohol or lacquer thinner or acetone to kill any grease that might be there and coat with the sharp edge coater.
on the 3rd screen try the dehumidifier environment and see where the results take you.
mooseman