Should/Can we coat out in the open shop or use (dark rm environment)?

[Shawn (EIP)]

Why would anyone leave the lid off the bucket while coating anyhow? Once the coater is filled I put the lid back on. Also who coats in the sun?

[Gilligan]

I think for the most part we are talking about people that coat with spill in sun light from a window or an open bay door.

The argument Dan is making (if I have this right) is that even cracking it open and filling up your scoop coater in said ambient light is bad for the emulsion.

[Dottonedan]

G,  no blood loss, no foul. . I don't wen remember us ever having any heated discussions in the past. I'm like that. I literally don't hold on to that stuff to long. Heck, Frog was made at me for a few years I guess. Never knew it. He had to tell me three or four times before I'd stop asking him. " what's was it you were made over" then that'd piss him off to just have to tell me again. It was something hatless to me but apparently stuck a cord with him. He loves me now.

Anyhow, I replied to say something intelligent yet forgot what it was.

[Dottonedan]

Yes,

The argument Dan is making (if I have this right) is that even cracking it open and filling up your scoop coater in said ambient light is bad for the emulsion.

As the emulsion gets older, it gets gummier and is not the best to use for high def work. Thicker and harder to get a nice smooth coat. If I were coating for sim process, I'd switch to a fresh bucket. You can use the other older mud on your 110's

[inkman996]

Take this as you see fit but back when I worked for a major supplier to out industry and the graphic industry I worked with vast amounts of emulsion in,flourescent lit work rooms. We split larger quantities down to smaller quantities daily, we dealt directly with all major emulsion manus and not one of them had a bad thing to say about it at all and from what I understood they even manufactured quite a bit of their product in,direct light. I am sure the manus know exactly what is considered safe and not safe even right down to the slightest in,easy table amount of accidental exposing. We can,all talk about small dots and the possible loss of them if coating in an open light room but what if that is not the case? How do we know with out the manus them selves coming here and telling us? I know for a fact we handled liquid emulsions in direct light with never an issue, we here print textiles but we sold emulsion to companies that used mesh as high as 700tpi that printed extreme detail way above any thing we do. As for cap film that is always handled with care in a safe light room.

[Prosperi-Tees]

Wouldn't opening and closing the darkroom door have an even more detrimental effect on dry screens than it would on wet screens? Seems logical.

[Binkspot]

I do believe Dan is correct, the light in the shop will affect the emulision. How do you grt rid of the last little bit of emulsion. You take the lid off set it in the sun and peal the cured stuff out.

Truly a question out of ignorance here (I'm still on my first gallon of emulsion... hence why I'm probably not qualified to really take part in this discussion).  I just dig the science.

Anyway, wouldn't that last bit of emulsion work the same way if you just left it open in a dark room where it could dry out?  Isn't the leaving it open in the sun also a way to dry it out quickly as well?

I could be completely wrong as I said, it is truly a question of ignorance.

Some emulsions have a shelf life after mixed so we dry the last bit out before tossing if we hadn't used the whole bucket. You could also say I'm cheap and want the bucket.

I keep the last bit out of the bucket to coat the screens instead of tapeing sometimes, mostly on screens we keep for repeat jobs or our number system.

[Rick Roth]

I doubt that anyone on this list has the capability to test this. There are too many variable to absolutely control to get superior test results. Probably even emulsion companies might have a tough time testing this.  When was the emulsion manufactured exactly? Do you have a finely tuned machine coating that can control the emulsion thickness? Are you going to test it on all mesh counts? Test it on all thicknesses of how you might coat a screen? Is five minutes of light negligible? How about an hour? Two?

We all use an extremely crude process call screenprinting, which means we have to push it to its limits to get outstanding results. Screenprinting has so many variables, some of which are very hard to control or you can't control them. So it becomes even more important that you control the parts of the process that you can. You can do screenprinting effectively with a variety of people coating screens, in hot and humid conditions, with a variety of manufacturers emulsions, with different types of exposure units, with a variety of ways of making your films, ....   However, go ahead and use the worst of any of these situations and you will have trouble even printing Whatsamatta U on the front of the shirt. Good screenprinting is all about controlling or eliminating variables.

For best results you want to control all these aspects and buy from manufacturers that sell good consistent products (consistency actually more important than good), have the same person at least coat if not using a machine coater, climate control as best you can... etc.  Can you quote your screens in low light?  Sure.  You probably could do it sometimes in direct sunlight. Would I recommend it?  Of course not. Light exposes emulsion. So does heat for that matter.  These are two variable that are not that difficult to control, so why would you not control them? Shops that have superior results have safelights in the screen room and try not to keep coasted screens around for to long because heat will also pre-expose them.

I have been in shops that coat in lit areas and they are doing screenprinting in those shops, so I'm sure you can do it. And if suppliers say it is ok, then maybe it is but in my years of doing this I have grown wary of suppliers advice. When pressed you find out that they often don't know why they advise as they do. All shops are not the same and so you can't always know the effect that something will have on one shop over another. 

I would recommend safelights. They aren't that expensive and therefore would be one of the first things I would do in a new shop.

[Gilligan]

Well said Rick.

[inkman996]

Rick you are correct we should control the variables that we can actually control but to what extent? At the end of the day we all here are t shirt printers should we strive to print dots smaller than the weaves of the t shirt it self? Should we st,rive to control variables to the point it's more expensive than to be practical? I am certainly not saying we should throw all our controllable situations to the curb and all become gutter printers I just feel in a process talked about here for textile printers coating in an open flours room it is acceptable.

I think this could be tested crudely but enough for textile printing purposes. A person can with a high tpi mesh screen coat one in a safe light room and then in a open light room then expose extremely low percentage tints and then examine with a loup. It would not be perfect but surely enought for textile printers. If there is a noticeably difference in the exposure I will gladly accept the theory that it is not safe to coat in open room if striving to print super high end sim process work.

[Gilligan]

You would have to coat a handful of screens in both conditions to at least achieve an "average" to make sure it wasn't one of the other hundred variables that could cause a difference.

[Dottonedan]

Testing a new bucket coated/used in a dark room, tested against a new bucket out in the shop will not be an accurate test. You would need to compare old buckets. (last coatet) of a bucket in each location. I'll also add that a 1 gallon is not going to show (as much) results as having a 5 gallon.  Each case (shop) and your amount of times leaving it exposed to regular light is going to make that difference.

[GraphicDisorder]

I would suggest its likely it could affect it, just not so likely at the amount of time/light that are in some of these shops.  My shop is not super bright.  We coat right out in the open, lights on.  Never noticed a issue vs when we use to shut all lights off and coat that way. 

What I did notice, is that we could see what we were doing better.  LOL

[Prosperi-Tees]

I would suggest its likely it could affect it, just not so likely at the amount of time/light that are in some of these shops.  My shop is not super bright.  We coat right out in the open, lights on.  Never noticed a issue vs when we use to shut all lights off and coat that way. 

What I did notice, is that we could see what we were doing better.  LOL

Where do you store your screens?

[ScreenFoo]

I'm still of the persuasion that open windows could affect this much more than fluorescents, as well as the real damage being done to the coated screens--not the bucket of emulsion.  IMHO, Inkman makes a great point--cap film you're extremely careful with, because it's already a thin sheet with loads of surface area, whereas a coater full of emulsion, or a bucket, only has a very small amount of surface area vs. mass.

RIck makes a great point as well, considering how easy it is to make sure you don't have to worry, why take the chance?

And again, although I have no hard and fast evidence on exactly what would happen--From what I know, a weaker stencil is guaranteed with more exposure to light.  How much weaker is the real question.