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

[Gilligan]

Taken from the Orange Emulsion thread:

We coat outside in the shop, store the coated screens horizontally in the dark room till they dry, then they are put along the wall based on mesh count.

[Dottonedan]

Interesting.  So,  (he coats outside)    like in a safe light room out in the shop....right? 

[Gilligan]

When emulsion is still "liquid" it isn't really that sensitive.

I don't think his shop has windows but it has large roll up doors... I'm betting it doesn't bother him or the emulsion if those doors are open.

I wouldn't coat in direct sun light (but I wonder if it really would hurt much).

[Prosperi-Tees]

I coat in the shop with the rollup door open. I don't even have a dark room, I just have screen racks covered in black fabric.

[Binkspot]

There are two large windows in the front of our building 5'x 5', one about 3' off the floor which is frosted the second 12' off the floor facing West. My screen closet and coating area is right in front of them. I try to coat in the morning before we start the day so its not to bright.

[alan802]

I've coated in a dark room for years, and the last few months we have been coating out in the shop under the lights.  I've spoken to several guys who know a lot more about this subject than I do and all have said that it is perfectly safe to coat where we do it.  Even the Kiwo rep I spoke to said it was fine, especially with the dual cure and diazo emulsions.  The way I understand it is when emulsion is in it's most liquid state, it is not light sensitive enough to cause any issues while coating, but once it starts actually drying, it needs to be in a safe light environment.  If there was a noticeable difference in being able to hold dots I would have noticed, and I've been very observant with our screens since we've started doing this to make sure that it is ok to do.  Even when some gurus told me it was fine to do that, I still tested it before I completely committed to doing it this way.

[Dottonedan]

When emulsion is still "liquid" it isn't really that sensitive.

I don't think his shop has windows but it has large roll up doors... I'm betting it doesn't bother him or the emulsion if those doors are open.

I wouldn't coat in direct sun light (but I wonder if it really would hurt much).

Sheesh.  Ha!  You creepy crawlers are just trying to entertain me on a Fri afternoon right?  You're joking right?  It's "light sensitive". any time in the light takes away from it's strength...and for every second in the light, you are depleting your strength. You do'nt see it in your (one screen) but I bet if you take an emulsion bucket just opened and one that you've had out coating in the light for a week, you would see a major difference in the ability to hold small dots. You'd have to do a new exposure test allover again on the new bucket  (because you are currently exposing to what your shop is accustom to) and that is pre exposed- light sensitive emulsion.

Where is that guy that kicks people in the "boy's".  I need a job done. Ha!

Ok. I know what you might say.

I do great halftones and great screens

.  Yes, you probably are very satisfied with your results, since you had to compensate way back when you had "some problem" trying to get everything to jive right. So you adjusted your exposure times or did this or did that, cuz you couldn't figure out what "the" problem was at the time. So you ended up with a band aid and yes, it works great for you now.

Well, here's your problem, or at least one that I can see.  Ok. Don't believe me. Oh yeah, you say what?  you want me to prove it?  ok. I'm gonna prove it. Let me get back to you.    Don't believe those flippn' crazy guru's. They aren't authentic guru's.

I was editing whilst Alan was posting. LOL. Alan, I respect ya buddy.  I even love your guts and revel in your glory of a great shop that you have. I do believe that you are getting great results.  I will say that you are getting those with a band aid effect. Not that it really matters a heck of alot. Pierre was getting great results as it was was too. He use to walk from one side of the shop to the other with a fresh screen to expose it. He swore it didn't affect it much. After some small changes, it showed  the difference to the good. I just don't have that specific info as to what that was.

If some "guru" is telling you that it doesn't hurt that much, they either don't really know or are insulting you for assuming that you will not be doing high end work and don't need your exposure times to be as accurate as they can be. Once you adjust, they do burn well. (what does that adjusting cost you tho?  Is it $, exposure time?  I haven't even checked yet and am confident I'll find the answer. If not, then I'll eat some crow and Alan and G can kick me in the boy's. Figuratively.

Am I being like an arse? I probably am, but really, I'm just loving a challenge that I brought upon myself, initiated by myself. I figure you all are saying, Who gives a patootie, my screens are fine. Well, I wasn't trying to be a smart arse. Just wanting to make double sure. You all "could be right" but it's highly unlikely.

[ScreenFoo]

Thanks Dan.  (I love ya)

Same thing happens to emulsion when exposed to light when wet as when you expose a humid screen--the diazo crosslinks with water--making a useless bond--at least with a diazo/dual cure. 


Edit:  I have very little experience with SBQ emulsion, if there's some reason they are totally different, I'd love to learn the how and why.

[alan802]

I believe one of the guys that said it was ok to coat in a flourescent lit room was Richard Greaves, but I'll have to try to find that to make certain.  One of the other gurus is the technical sales rep for Kiwo so I think he knows a little bit about it and hopefully he isn't insulting me.  I think there is a possibility that you are right Dan, and coating where we are might be keeping us from holding 100% of our halftones versus the 98-99% that we are holding now, but just as adamant as you are about this not being a good idea, I'm equally as solid in my opinion that I can't hold one single percent more halftone dots if I coated in a light safe room.  Trust me Dan, I'm certainly not thinking you're being an ass, I like this kind of debate and we're all adults here and I think we can debate this without anyone's feelings getting hurt.  Something good will come out of this argument as long as we all act like adults like we have thus far.

Not that I don't trust your thoughts Dan, not at all the issue, some of the guys that have said that coating in an average UV light setting is ok are really some of the best and most knowledgeable guys in the industry.  I don't know if they'd appreciate me throwing their names out in this debate but I'll contact them to see if they don't mind or perhaps would like to join the discussion. 

If by chance not coating in safe light is really not a good idea, I'll probably move things back to the way they were, but honestly, I can't see the work that we are trying to do with 55 lpi halftones is going to be negatively affected by doing things the way we are.  Like I said earlier, I have not noticed any issues, but maybe we aren't doing the quality of work here that we would notice.  I'd like to think that we are, but it's all subjective.  If I have 1000 halftones on a certain stencil, and I'm losing 10 of those during prep, and I can keep those ten by coating in a safe light room, I'm the kind of guy that will move to the safe light room.  It might be a lot more significant than that, I'm just throwing out some numbers for shats and gaggles.

It's all good Dan-O, I enjoy this, we will all be better off after this thread is all said and done.

[Dottonedan]

Ok. I feel ya. I know where you are coming from. I think when I really dissect where I feel it makes a difference worth debating over is in accurate or ( optimum exposure efficiency) resulting in a faster (exposure times). being able to go from 4% dot to a 3% dot may also be possible with a more accurate exposure, but that is just where the results really should have been. I think you would have an additional improved result.

If your Wet emulsion that you opened on Tues. is already exposed by ( lets say 1%), after 2 days of being exposed to light for a few minutes, a couple times a day, then  another 2 days its been exposed by ( lets say 3%) and by Monday, you open it up and coat using the last of it and its been exposed at 5%, then that has to play a role on exposure time. Your exposure results will be slightly harder to get an accurate exposure than let's say it could have been with protected emulsion.

This is common sense and I don't think anyone is going to argue that this part would be true. So, the real question is, how much of a difference does it really make? This question is going to have a different answer for each shop. This is not a life threatening choice like smoking, but it's like saying, smoking affects everyone differently. The fact is, its not the best way to handle treating your body. You really shouldn't do it but you can choose to. Exposing your emulsion to light is sort of similar. Here is why.

A shop that opens a lid 1 time a week in daylight for a gallon and takes 4 weeks to use it up will not experience much of a difference. A shop that goes though a 5 gallons a week opening and closing a lid multiple times a day ( in daylight) should be measurably adversely affecting your exposure time. As an example, Your quality results are going to change from the coated screens freshly out of the can to the end of the bucket.

[Prosperi-Tees]

My biggest problem with not having a dark room is dust. I really can't keep my screens dust free. When I move shops that is the first issue I will address for sure.

[Gilligan]

...
If your Wet emulsion that you opened on Tues. is already exposed by ( lets say 1%), after 2 days of being exposed to light for a few minutes, a couple times a day, then  another 2 days its been exposed by ( lets say 3%) and by Monday, you open it up and coat using the last of it and its been exposed at 5%, then that has to play a role on exposure time. Your exposure results will be slightly harder to get an accurate exposure than let's say it could have been with protected emulsion....

Don't take this the wrong way but Dan, you are basing your entire premise based on completely made up numbers.

You don't know there is a 1% exposure when you open the lid.  What if the actual exposure is .0000001%?  If you base your calculations on that made up number it is completely insignificant for ANY textile work and probably most other uber delicate work.

We need someone with true chemical engineering knowledge of how emulsions work and are effected in different states (liquid in this case) to have real data to work with.

For academic purposes (though it would serve no real practical purpose) I wonder how long it would take for emulsion that is constantly being churned/stirred to crosslink or anything similar to that if in a bucket exposed to the sun.

If you kept it moving then it wouldn't be able to have a surface skin that could "dry up" and crosslink and then you would have a small clue at how much daylight would effect it.

If you wanted to make this a semi-practical test, you could take said bucket and pull some of the emulsion out after an hour of this "churn and burn" and coat a screen and then run an exposure test.  Then wait another hour and do the same... blah blah blah rinse and repeat for as long as you like or until it starts to make a measurable difference.

Then maybe with that data you can extrapolate some real numbers at how it effects it.  Still WAY too many variables in this test for concrete numbers, but it would be interesting data none the less.  If you want a bit more scientific numbers then you could use an exposure unit for your light source and then maybe you could log light units as a reference for "time" exposed.

Simply saying someone will have to increase their exposure time because of moving their coating outside of a light safe area isn't all that accurate.  Alan, did you guys have to change anything?  They just moved from light safe to non-light safe and if anyone would catch something like that I am certain Alan would.  Is he doing lab accurate testing? No, but it's closer than guessing based on gut feelings.

Please take all of this in the same pursuit for the truth as anyone else already in this discussion.

[Sbrem]

This turned into a great discussion. We coat under yellow sleeved fluorescents, dry in a commercial drying cabinet, and store in dark cabinets. Set up under the aforementioned yellow, and the washout area has some ambient outdoor light, but mostly yellow. For years we worked in really dark, dim light, but it was overall bad for the eyes, and using the bright yellow lights didn't change our quality. It did the lose the dungeon feel though. My thought on the sensitivity is that if the sensitizer comes in a brown opaque container in a box, it must be sensitive, I don't see why wet or dry would make a difference. If you coated the screens in normal daylight, which is rich in the wavelengths that affect the emulsion, then some pre-exposure has to be happening, which I would liken to laying a neutral density filter on your screen, so that when it's exposed, the very finest detail would be the most affected, as it's already slightly undercut. So, in an example like Pierre's Blue Moon shirt, where the grain size of part of the image is from 280 ppi resolution, then those ultra-tiny bits may or may not come out; some 3" letters in Impact font probably won't exhibit any issues. I vote for safelights.

Steve

[Dottonedan]

Simply saying someone will have to increase their exposure time because of moving their coating outside of a light safe area isn't all that accurate.  Alan, did you guys have to change anything?  They just moved from light safe to non-light safe and if anyone would catch something like that I am certain Alan would.  Is he doing lab accurate testing? No, but it's closer than guessing based on gut feelings.

At the beginning of opening the bucket of emulsion, his exposure time is still the same as at the end of his opened bucket of emulsion a few days or weeks later. I'm saying that at the end of (any company's 2 weeks of having an open container of emulsion) will have adverse affects on the image stencil.  It might not be "noticeable to Alan or Joe or Tom, but it's noticeable to some company over time.


If Alan does the type of work that most average shops do (basic spot color prints), for the biggest part of his business, nobody would think of changing exposure times once switching from a dark room to out in the light. The affect is not dramatic or instant, it's over time. It's like saying, I looked straight into the sun and nothing happened so those people who say "Don't look into the light because the UV rays are bad for your eyes".


Lets face it. We are all human. Even a Super seasoned coater might miss this. The thing is, he's happy with his exposure times right? So "the way he's doing it now, (the results he gets) he's ok with. Even tho, the results may be inconsistent from beginning to end of open emulsion. One doing this might even say, "coating screens in daylight does not affect my exposure times".

When I say "inconsistent", it may never be really noticed because of the randomness of screens and art on those screens coming in every day.  One day of coating (with the bottom of a 5 gallon bucket of an old emulsion that has been opened out in the light, he might coat 7-110's, 2-86's, 10-230's & 4-305's In that mix of 305's, he might only have 1 (one) 305 mesh that had 6% dots in the art. Once exposed, it might not come out all the way. It might be a little saw toothed. Why? Does your screen room guy even notice? If he does notice, does he mention anything? Would you normally tell him to toss that one out and burn another screen because the 6% dots did not come out or would you just use it?  Many shops would use it on a normal basis so it goes unnoticed.

You might have at one time called on Kiwo tech support and you say, I am out of room in my dark room, can I coat my screens out in the shop in day light, will this affect my emulsions? Your "guru" might say, "Ahe, it's not a problem for you."  because maybe he knows your 1% of your screens in a day that require holding 4% in a 55 line screen.  Does it affect your exposure over a long perod of time?  Yes,  Is it significant enough for you to make a change?  That is up to you and the amount of work and level you want to maintain as your standard.

So, with all the stencils burned that day (with that old pre-exposed emulsion), you got 1 (one) mesh that missed holding a few lower dots. Nobody lost a limb or life over it and more than likely nobody said "Well, shoulda not used that bottom of the pre-exposed emulsion". Nobody in the every day process would notice or care that this was the source. All the while you are thinking pre-exposed emulsion it does not matter).

For this type of detail, maybe it doesn't matter for your shop. Maybe that is the norm and nobody is the wiser. Maybe this is why one can say "I never changed a thing and just started coating outside in the light. NO difference.

Where does this affect us?

1st, maybe in how we provide separations. Maybe you tell your sep artist that you know you can only hold down to 6% dots so change everything to show 7%. (so that had changed).

2ndly, Your exposure times are consistent....but are not at optimum for all screens (for your varying strengths of emulsions).

Taking this to even more extreme example, imagine a shop that only did low mesh, big and bold type like athletic printing. This would not matter to them at all. They could hold all it and never flinch as you can often get away with over exposed BIG BOLD TYPE.

Imagine a shop that did nothing but process and sim process and are known for this. They specialize in this area. 230's, 305's and 350 mesh. Would the pre-exposed differences between a fresh can and an old can make a difference?  I think it would.

[ScreenFoo]

For debates sake, the delineation between fluorescent lit room and sunlit room needs to be made--the sunlight will expose any emulsion unusually quickly--overhead fluorescent lights will not.

If Alan is talking about coating in a shop lit with fluorescent lights, I can't see much of a change happening between that and a 'light safe' environment.