TSB
screen printing => Screen Making => Topic started by: Rockers on June 03, 2017, 03:50:19 AM
-
Hoping for recommendations for a good photopolymer emulsion that works great high humidity and is not tacky. Chromaline used to have one for a short period of the , Chroma/Tech TD but it has been discontinued. Apparently they are working on a better version now but no release date yet. What else is out there that might fit the bill?
-
Whats available in Japan?
-
Back when it was my regular emulsion, Chroma Tech PL wasn't noticeably tacky compared to the cheaper ones I have used for the last few years. I find that lightly dusting with talc is worth the $40 a gallon savings. ;D
For that matter, I seem to remember that Ulano QTX was fine as well in that respect.
-
We have no problems with Saati PHU in a high humidity climate but we do have a dehumidifier and air conditioner in our screen drying room.
-
I just started using baby powder on every screen. Works great.
-
Whats available in Japan?
I buy most our supplies in the States and have them shipped to Japan. So everything from Chromaline or CCI and others.
-
The Saati PHU worked great for us on a nuarc 3140.
With multiple brands, we would experience screens being tacky from the heat from the exposure unit.
So we tried out a few and stuck with the PHU. Plus it is water resistant with a very wide exposure latitude.
It downside is that it can be on the brittle side, the emulsion will crack under pressure if its to dry - squeegee edges will wear a path through the emulsion, which has been talked about in the past.
It is definitely one to put on your short list.
-
We experience No tackiness with CryoCoat and our screen room climate can swing a bit with the weather
Sent from my XT1585 using Tapatalk
-
Chromaline says that they've put the non-sticky/humidity resistant properties of the TD into their Chromalime emulsion. The new line should be rolling out soon.
-
Ulano QXO is good. Also, call/email Kevin at River City and try out his Chromaline Prototype emulsion. It's the least tacky pure photo emulsion I've ever used, and I've tested close to 25 different emulsions just in the last 2 years. Emulsion tackiness has been a huge issue here at our shop, even with our dark room being very well maintained at 25-30% humidity. The Prototype is one of the only emulsions that we don't have to use baby powder, but we still put it on there for lower mesh counts. The QXO is my favorite all around emulsion right now but I use the Prototype all the time as well.
-
We've been running Murakami t9 and really like it. It doesn't seem tacky, but we are CTS, so I've never put film against it.
-
The T9 still gets tacky on glass :(
-
Can someone explain the baby powder procedure? Its crazy humid here in VA and we need a solution... every single screen we are exposing here we have major ink transfer / bad film sticking.
Are you just dusting the back of the screen with the powder before you place the film? How much are you using? Does it interfere with exposure?
thanks!
-
Plasticizers in pure photopolymers can get tacky in humid areas or on a hot metal halide exposure unit. A little talc or baby powder on the screen before exposure and spread around the screen solves this issue. Talc powder will not create pinholes if you spread it around. Preserves ink jet positives.
-
Can someone explain the baby powder procedure? Its crazy humid here in VA and we need a solution... every single screen we are exposing here we have major ink transfer / bad film sticking.
Are you just dusting the back of the screen with the powder before you place the film? How much are you using? Does it interfere with exposure?
thanks!
A light dusting is all you need. Just enough so that a very thin layer covers the area where the film is going. I leave only the tiniest of holes in the adjustable lid then spread it out with my hand. It should only take 5 seconds or so per screen. We've had to do this since we moved away from dual cure and started using PP emulsions. Some emulsions are even tacky enough to resist a large amount of powder, but it's usually the VERY high solids content PP emulsions, like around 50% solids content or higher.
-
Thanks for the info!! Will be implementing the powder trick until we have time to play with some of the suggested emulsions here. Tackiness has been a big problem for us. Trashed 10 of 20 positives today.
-
Baby powder helped save films for repeat orders. Ulano Orange had minimal tack and my local sales rep wants me to try Ulano Blue. Saati PV has been the tackiest so far. Cryocoat wasn't too bad but I think Ulano Orange was the least tacky that I've tried this year so far.
-
Thanks for the info!! Will be implementing the powder trick until we have time to play with some of the suggested emulsions here. Tackiness has been a big problem for us. Trashed 10 of 20 positives today.
You may find the powder trick to be sufficient if you like your current emulsion a lot. It's one of the few "bandaids" I don't mind doing around here. I did spend hours upon hours trying to figure out how to get regular emulsions from eating our positives and now I would rather find a good emulsion that we like, that has minimal tack and use the powder.
-
CCI HXT you'll love it
-
Thanks for the info!! Will be implementing the powder trick until we have time to play with some of the suggested emulsions here. Tackiness has been a big problem for us. Trashed 10 of 20 positives today.
You may find the powder trick to be sufficient if you like your current emulsion a lot. It's one of the few "bandaids" I don't mind doing around here. I did spend hours upon hours trying to figure out how to get regular emulsions from eating our positives and now I would rather find a good emulsion that we like, that has minimal tack and use the powder.
I sometimes cringe when the term "bandaid" is used as a temporary or even half-assed fix because, in the real world, actual bandaids are often exactly the fix one wants. Not every cut requires sutures.
-
We tried Chromatech WR and it was insanely sticky. Film was fused to the emulsion.
We're on Ulano Orange in the meantime.
Sent from my iPhone using Tapatalk
-
Not sure if this one was mentioned yet, but I'm currently using Ulano Blue and there is zero tack on even the most humid days. I haven't been using baby powder with it and the films come off perfectly.
-
Why don't you just turn the heat up in the drying room. The emulsion can only be tacky if it's full of moisture.
-
Not necessarily true
-
Not entirely, but highly probable.
Click the fan heater on high in the morning, direct the flow of warm air across the rack of screens intended to expose, but don't touch them till 10am. I'd hazard a guess there would be a noticeable improvement.
I'll take a stab and say the tackiness in most part is inkjet film sticking to the stencil. Why?
-
The heat from exposing and using the glass (keeping a lot of the heat in) I'm sure adds to the problem. Cooling down the exposure unit better / not using it as fast between screens (see if you can add coating at the same time as making screens?) would help.
I'm glad to be rid of that problem with CTS. I do remember some films sticking really bad when the temp and humidity was really high in the summer.
-
I have the same. Film sticks when humidity climbs up to 50%+ and first thing in the morning. I have a 10'X10' room with a domestic dehumidifier that runs 24h and the little fan heater gets clicked on high first thing in the morning.
If I can maintain a ratio of 30% humidity and 35 degrees in heat, film sticking isn't an issue. Outside of that I'm blasting black inkjet film off my stencil or peeling the frame off the glass regardless of emulsion.
I just make sure I'm setup for the following morning the previous afternoon to overcome the gap in waiting for the heat to climb.
I've been using a Roland ecosol printer for film for the last month through necessity , I don't have that sticking problem while I'm using this.
Generally I'll use Ulano QTX or QX1, Foteco 1850 solo.
M&R trilight 3kW.
I might run things hotter in the drying room because I'm generally impatient anyway, but ruining film I might need to expose again drives me nuts, as does washing the black ink out of my exposed stencil. And heat is how I overcome it, it's not excessive heat either IMO.
It would be interesting to hear how someone with something like a vastex drying cabinet or that type of generic screen cabinet gets on and whether they suffer from this specific problem.
-
The sticking is generally a chemistry issue.
While yes, humidity will always play a roll. If you have eliminated the moisture issues, what remains is the plastisizers in the emulsion. Under heat, these plasticizers are tacky and grab at all films. Waterbase films exacerbate the issue compared to silver or laser films.
Tldr: If your screens have an average of 35% internal humidity and they are still sticking during exposure, either change your emulsion or use baby powder/talcum powder.
-
Why don't you just turn the heat up in the drying room. The emulsion can only be tacky if it's full of moisture.
I don`t think so.
-
Why not?
You didn't elaborate on the effect of tacky stencils, or what it's doing that's causing you to look for a cure. If it's just a case of everything working as it should then that's probably not a problem.
Reading what others have said they have film sticking to emulsion, destroying their positives. Perhaps wrongly I'm assuming inkjet positives.
Do they have the same problem using image setter film or solvent film? If these two films are sticking, but peeling away unharmed and the stencil is still washing out fine, that's not a problem is it?
I guess to answer the question without elaborating. Ulano QTX, is fine, no sticking problems what so ever. No need for talcum powder, the emulsion never sticks to glass, your inkjet positives are perfectly fine and peel away unharmed, with only the slightest hesitation after having been compressed with vacuum for as long as it takes to expose whatever I'm exposing. Actually I don't have a problem with emulsions being tacky at all, at least not all the emulsions I've tried.
If I was to elaborate on that, I only ever achieved a non tacky emulsion (regardless of make up), that would cause problems in keeping inkjet film in good reusable condition, when I eliminated moisture from my stencils as best I could. In saying that, I might just be lucky.
I'm not going to delve too deeply into it, I don't know the science. I just know inkjet film isn't sticky, but when I lick my thumb and grab an edge of inkjet film it's sticks to my thumb like a bastard, and that tells me moisture effects inkjet film and if any moisture comes in contact with the inkjet film and is compressed under pressure for a few minutes, then the film is going to stick to whatever it's in contact with like a self adhesive label. Likewise, glass doesn't have any adhesive properties so any problem associated with emulsion sticking to glass would have to rightly boil down to emulsion, so why not look at moisture content of the stencil as a reasonable cause of tackiness there too.
That, or it seems folk swear by talcum powder with no ill effect and minimal fuss, I'll give it a go myself sometime.
-
I think Humidity is the issue, not heat. Screens dry in our shop overnight in the Winter without any added heat or dehumidifier and they are less tacky. Some emulsions are, by nature, just more tacky then others. The only time I've had the film sticking issue is when using Saati PV. Ulano emulsions just seem to do better in the heat/humid climates, IMO. This is the case for our shop at least. Everyone's work environment is different so results will always vary.
-
The sticking is generally a chemistry issue.
While yes, humidity will always play a roll. If you have eliminated the moisture issues, what remains is the plastisizers in the emulsion. Under heat, these plasticizers are tacky and grab at all films. Waterbase films exacerbate the issue compared to silver or laser films.
Tldr: If your screens have an average of 35% internal humidity and they are still sticking during exposure, either change your emulsion or use baby powder/talcum powder.
This
-
I agree it has nothing to do with drying the screen's in most case's, take Chromatech WR emulsion that stuff will stick a film in a heart beat compared to the CCI HXT. I use both and found out that drying them both the same didn't work, so I dried the Chroma longer and still got sticky films, I think it's the solid's in the emulsions like Colin stated you can dry all you want and still get film sticking so break out the baby powder ;D
-
The only other thing I can possibly think of regarding this issue that I might do differently, or which might be helpful is I've had a habit of leaving my inkjet film in the screen room to dry alongside the screens, pegged out on a curtain wire on the wall. There's no particular reason for me to do this other than it seemed the obvious place to leave my fresh wet inkjet film positives to dry. Often I might pull dry coated screens out the rack like drawers and throw my positives on top of a few screens.
Whether there is some voodoo involved in matching a dry stencil with an equally dry film positive to avoid this problem. Or another possibility is its the film positive itself that takes just enough moisture from the atmosphere and carries it to the stencil to react poorly and stick in the vacuum situation which I've never considered, but I've probably been lucky in avoiding that for the reason detailed above.
I don't use waterproof or water resistant inkjet film. I use the cheapest I can find. If it's dimensionally stable and works through my printer and costs less than someone else's roll I'll use it. I found no difference between any variant for the sticking issue anyway.
Oddly though, I know exactly when this problem arises for me and I can see it happening and avoid it.
It's only ever evident on the lower mesh counts - 43T and 59S mostly. You'll almost never see it sticking on a 90, 120, 150 (metric) regardless of how rushed you are. Temperature here swings widely between seasons and I can enjoy weeks on end of 90%+humidity in summer.
What I find hard to accept, is a manufacturer will place product into the market that doesn't work. Especially our industry. Is an emulsion manufacturer really going to send product across the planet to all its resellers and not test it thoroughly? For something as simple and common as how it works with inkjet film? In all conditions?
Come on now, have a think about that.
-
We use the Chromatech WR and yes it is sticky as all get out but I believe it was chemically engineered for CTS we don't care. Exposure=3 seconds
-
Photopolymers can be sticky due to the products used to make it and does have benefits. Use a diazo emulison if you don't want any stickiness at all. Baby powder solves the day and gets you a fast exposing emulsion. We build our emulsions to be durable and have the highest resolution possible. Sometimes that tack is important. The surface tension of direct to screen imaging is better, the dots hold their shape. Or if you are doing a 65 line with real film, the dots will be intimately pressed to the emulsion to avoid halation, especially in 10% and below. Your inkjet printer to film rarely makes a good dot below 5%, thats why it is hard to image and why pure film has such perfect halftone shapes. So Pure Photopolymers have less pinholing, less breakdown when shot well, and have tack that aides some printers and yes it will destroy an inkjet positive in hot humid conditions. Keep your room at 70-75 degress and 35-50% humidity for the least amount of tack.
However, baby powder is such an easy fix for inkjet film users and photopolymers that you ought to try it! No pinholes created, film peels off easily, screens shoot fast, and better edge quality.
Al