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screen printing => Screen Making => Topic started by: Rubysky on January 16, 2017, 05:09:54 AM
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Hello,
What is the exposure time for Murakami SP-Pro with M&R Starlight UV Led Screen exposure system.
Thank you so much.
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I'd suggest a call or email to Murakami, to get a base approximation of time (since LED may not be included yet on the tech sheet ). Then, use an exposure calculator or use their instructions on how to perform a step test (http://murakamiscreen.com/technical-support/step-test-instructions/)
Keep in mind, that though all exposures made with the Starlight will be fairly quick, mesh count and coating technique will change times.
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Hello,
What is the exposure time for Murakami SP-Pro with M&R Starlight UV Led Screen exposure system.
Thank you so much.
This is not enough information to go on. Mesh count, color of mesh, how you coated, manually or with an automatic, EOM of emulsion or how many coats will help.
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Hello,
Thank you so much for the reply. I am planing to use this mesh count;
110 (white)
155 (white)
230 (Yellow)
Nittoku/ Murakami S Mesh in USA 225S (Yellow)
Coating; 2x printing side, 2x T-shirt side.
Emulsion type; Murakami Diazo Type Sp-pro
Murakami told me to start at 60 sec.
But the exposure machine I use is M&R Starlight and I heard it expose screen very fast.
Please advise.
Thank you.
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Hello,
Thank you so much for the reply. I am planing to use this mesh count;
110 (white)
155 (white)
230 (Yellow)
Nittoku/ Murakami S Mesh in USA 225S (Yellow)
Coating; 2x printing side, 2x T-shirt side.
Emulsion type; Murakami Diazo Type Sp-pro
Murakami told me to start at 60 sec.
But the exposure machine I use is M&R Starlight and I heard it expose screen very fast.
Please advise.
Thank you.
The Starlight does expose (as fast as you may want it to), but the different emulsion have different times needed to fully cook the emulsion and cross link completely. So, lets say, maybe the Murakami does not expose (as fast) as other brands. Theirs may need more time for a full cure. That is not a bad thing. Even 60-80 seconds can still be shorter than a 3-5k MH. depending.
Your real goal, should not really be (fast exposure), but accurate exposure. Sure, everyone wants it done faster, but you really want a "good" exposure. So just expxose a tad longer to get it to fully cook.
Some people expose for X time such as 50-90 seconds and then will post expose (or expose again). All of that (number of seconds) pertains to (how) you coat. One persons 1:1 will be different than another persons 1:1. You, also on the other hand, are coating 2:2. That will also add time no matter the technique. I myself, like a good thick stencil, but it can be (too much) some times.
That 230 mesh, now that I looked at it, really should not need a 2:2 coat. That is too thick for a 230. Some people will do as little as a 1:1 on that mesh...to hold good detail.
Also, (if printing your images from a DTS), and burning on a Starlight, and you do a stouffer's step test, the more accurate exposure # you want will be a 6. If on films, you want a 7. With a DTS, you are removing two variables. Films and Glass. So a 7 is not the desired number.
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Hi,
Thank you so much for the detailed reply. I'm just starting out with silk screen. My past experience is Digital Printing. But I want to shift some of the production to silk screen for bulk order. DTG printing takes very long to print one t-shirt and the ink cost is unbelievable.
Mesh 230 1;1 noted.
230 lower mesh I will try 2;2
Murakami advise me to do 2;2 let it dry then 1;1. But I think that much emulsion on the screen might be too much.
I don't think the Murakami in Japan has seen M&R LED exposure machine yet. Last I check only 2 vendors is using this machine so the number they gave me might not be accurate (60 second exposure time). That is why I come to this forum to seek an answer. I will coat several screens today and set the time to 60 sec to expose the screen and see how it goes.
Can I use a liquid dishwasher to degrease a new screen? Murakami here told me to just use sticky roller tape to pick up dirt from the screen, no need to wash.
I hope the end of this year I can buy auto coating machine and auto press. Doing a lot of research now for those :)
Thank you so much, guys.
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I think you might be either misunderstanding what they are telling you...or they are misinformed themselves and (they) should be the least uninformed about their emulsion.
You might want to review with them again. For example, one would not normally coat a screen 2:2, let it dry then coat 1:1 unless you were going for some high density printing to where the ink is put down very thick. Stacked.
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[/size]Forums are great... and ours is the best, (we now have an award to prove it). ;) but "typically", if you want the best information about the best methods of using a specific product, you want to contact the manufacturer or the specialist in the suppliers screen printing department.[size=78%]
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Can I use a liquid dishwasher to degrease a new screen? Murakami here told me to just use sticky roller tape to pick up dirt from the screen, no need to wash.
I highly suggest not using a liquid dishsoap as most of them contain lanolins which will cause adhesion issues with the emulsion. Some ink degradents (Easiway 701) contain a degreasing component in them, others require it, still other people who use mostly lower mesh counts don't degrease at all. At our shop, we use Saati products (Ir26 for ink degrading/dehaze, followed by DirectPrep2 for degrease) this combination gives a killer screen result with next to 0 imperfections in the coating.
If the Murakami SP Diazo is roughly equivelant to their SP1400, our exposure times for a 156/64 white mesh screen were around 70 seconds to a solid 7. Best advice is to get yourself a Stouffer strip and do some testing.
Generally speaking, the LED exposure units are super fast on pure-photopolymer emulsions, not so much faster on diazo's.
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Hi,
Thank you so much for the detailed reply. I'm just starting out with silk screen. My past experience is Digital Printing. But I want to shift some of the production to silk screen for bulk order. DTG printing takes very long to print one t-shirt and the ink cost is unbelievable.
Mesh 230 1;1 noted.
230 lower mesh I will try 2;2
Murakami advise me to do 2;2 let it dry then 1;1. But I think that much emulsion on the screen might be too much.
I don't think the Murakami in Japan has seen M&R LED exposure machine yet. Last I check only 2 vendors is using this machine so the number they gave me might not be accurate (60 second exposure time). That is why I come to this forum to seek an answer. I will coat several screens today and set the time to 60 sec to expose the screen and see how it goes.
Can I use a liquid dishwasher to degrease a new screen? Murakami here told me to just use sticky roller tape to pick up dirt from the screen, no need to wash.
I hope the end of this year I can buy auto coating machine and auto press. Doing a lot of research now for those :)
Thank you so much, guys.
on a one and one coat or a 2 and one coat on white start a 30 seconds on white mesh and 50 seconds on yellow. On the 230 yellow S try 60 seconds.
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Bears noting that post exposing a diazo may make you feel better but accomplishes nothing. Not so with PPs though
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LED units, including the Starlight, expose diazo sensitized emulsions much slower than a 5kw metal halide. So slow, that some core components overheat as the units are not cool running either. Ours is 109˚F on the outside of the blanket during screen production for an example.
It's unfortunate that many manufacturers sell the units on characteristics that do not apply to fully exposing diazo emulsions. If you are zapping PP emulsion for 1 second because you print plastisol and don't need to correctly expose your screens then some of those claims might ring true but for the rest of us, by and large, it's bunk. You can get acceptable and even very good results from LED but it's a downgrade form MH in every way but power consumption. We run LED because of power constraints.
On our starlight a 225/40 Murakami S screen coated 2/1 thin side of coater with diazo sensitized emulsion (not yours but this should be an ok starting point) exposes at 75 seconds CTS/no glass and 140 seconds with film and glass. This is 7 steps on the stouffer strip and acceptable resolution.
Hope that helps.
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LED units, including the Starlight, expose diazo sensitized emulsions much slower than a 5kw metal halide. So slow, that some core components overheat as the units are not cool running either. Ours is 109˚F on the outside of the blanket during screen production for an example.
It's unfortunate that many manufacturers sell the units on characteristics that do not apply to fully exposing diazo emulsions. If you are zapping PP emulsion for 1 second because you print plastisol and don't need to correctly expose your screens then some of those claims might ring true but for the rest of us, by and large, it's bunk. You can get acceptable and even very good results from LED but it's a downgrade from MH in every way but power consumption. We run LED because of power constraints.
On our starlight a 225/40 Murakami S screen coated 2/1 thin side of coater with diazo sensitized emulsion (not yours but this should be an ok starting point) exposes at 75 seconds CTS/no glass and 140 seconds with film and glass. This is 7 steps on the stouffer strip and acceptable resolution.
Hope that helps.
I say that holds true.."for your shop" and of course others (but not all discharge waterbase users). You might do things differently than another shop using the same emulsion and exposure unit on the same exp unit. LED is not bunk for all who use diazo. I know this. I've seen it, been at many shops doing/have been doing it all the time. What is their quality? I really didn't pay that much attention. I've also been in one shop using a 5k MH exposing 4 screens up at a time...on 110's needing exposed for 8 minutes while The I-Image was clicking away right next to it with the same emulsion, same coating. True story.
Have you tried looking at a step 6 without film and glass? It's being said many emulsion suppliers (and myself), that the 6 is where you should be for dts no glass, no film.
I say, it depends on the shop.
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I agree 100% with Chris on this topic of led vs metal halide. I've tested a ton of units and nothing led wise has been better then my trusty ole nuarc metal halide regardless of what test that is. Led has its place for 90% of users out there but my opinion is if you want repeatable top quality screens metal halide has an edge in everything except power consumption/bulb life. Led can produce some great screens but from all my testing I'll still take a metal halide unit over led.
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No, it does not depend on "my shop". M&R, professionals they are, confirmed the times using same mesh/emulsion/coating to make sure there wasn't something off with the unit or with our process.
And yes, if you are using diazo added emulsions, the claim that LED is faster and cooler is absolutely bunk. Apparently nobody tested that prior to selling the units and they weren't aware that certain diazos would have such long exposure times. The units overheat at the times needed to shoot diazos- our entire array needed replaced due to a heat warped board.
I'm hesitant to address your comment about an i image working faster than a 5k MH shooting multi up....I'll say that I love the concept of "insert screen, image, expose, resolve". I think that's great and a very natural workflow. But it is not faster than standalone imaging and MH shooting multi up.
Again, we use LED so it's not that I'm against it. Just putting down some facts.
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So I hesitated for a while on led units, actually returned 2 units because they didn't work on diazos(sp-1400). I had swore them off, very happy with our 5k unit. After running a dozen screens that I coated, imaged and then exposed on a LightSpeed LED unit, I bought one. Now we don't have 5 sec exposures, 55sec - 1:16sec. But I personally haven't noticed any difference from the quality screen we were getting from our 5k unit. I have not and will not use hardeners, I just refuse to.
I think you guys know me enough that if there was a issue, I'd be the first one to bitch 8)
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Glad to see much response :) Murakami Japan gave me that 60 sec mark as starting point. They do not have M&R starlight so they throw that 60 sec number base on the exposure unit they have in their office.
I notice a lot people in this forum do 1;2 or 2;2 coating on the screen. Murakami rep told me to do 2;2 let it dry and do 1;1 again. No, degrease.... Just use sticky roller tape to pick up dirt from the screen. They don't even sell degreaser here... I tried to purchase from the US but the liquid chemical is really hard to pass custom these days. Dish washing soap is bad so is there any other alternative? Or any shop out there that willing to ship chemical to Japan?
Thank you so much, guys.
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2/2 and THEN 1/1 - sounds like someone is trying to make more sales... We have been doing 1/1 for over a year now probably. We are pretty much a DC/WB shop though. When we did plastisol we would coat 2/2. That was Murakami HVP.
2/2 then 1/1 is just a waste.
Sent from my LG-H918 using Tapatalk
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No, it does not depend on "my shop". M&R, professionals they are, confirmed the times using same mesh/emulsion/coating to make sure there wasn't something off with the unit or with our process.
And yes, if you are using diazo added emulsions, the claim that LED is faster and cooler is absolutely bunk. Apparently nobody tested that prior to selling the units and they weren't aware that certain diazos would have such long exposure times. The units overheat at the times needed to shoot diazos- our entire array needed replaced due to a heat warped board.
I'm hesitant to address your comment about an i image working faster than a 5k MH shooting multi up....I'll say that I love the concept of "insert screen, image, expose, resolve". I think that's great and a very natural workflow. But it is not faster than standalone imaging and MH shooting multi up.
Again, we use LED so it's not that I'm against it. Just putting down some facts.
Yes it does. :)
I don't know much about "cooler". I have not been involved in, nor heard marketing it to be "cooler" than this or that. I've only heard them to say that it doesn't put off a lot of heat (if much at all)..and that has been my experience... and uses less energy. So I'm positive that what you say, is totally true and coming from you, I'd expect it to be so. But, having said that, I know (first hand) it's not "typical" in any of my situations to be very hot or hot enough, to cause a problem for all people. Again, my point that you and your shop have to be somewhat different than the average beast.
I say that from putting in and working on machines at over 160 different shops in me little time I was there with at least 15% of them being waterbase discharge printers.
Now, the LED exp have not been out for 10 years so we don't have a ton of people chiming in to provide that kind of feedback. I'll be the first to say, I'm no expert on the temp thing. You have experienced something with that. So you have every right to say your experiences. I didn't have that experience. I will say tho, I've not heard (one) person in the field say, Damn man, these things get hot! It melted this or that on it or I had to buy a new X thingy cuz it melted inside. Notta one, but that doesn't mean it does't happen. I might have jsut not heard about it while there. I musta went 2 years before ever having to replace a print head in one of the older machines and after I did, it continued to be a rarity. During my first year or so, I started to think that they just never went bad till that one day when I finally did replace one.
I don't claim to dispel your facts. They are facts indeed (for you) and that is my only point. What I'm saying is, I guess I take issue with the "blanket statements" as if it's done and done man, no if's but's or why's. It's THIS way and nothing else. I don't agree with that.
I just want to make note, that the experiences at one shop (given that you are a seasoned and more so a top level waterbase and discharge printer, ) the experiences at your shop may not apply (to all) Diazo users in this industry but could very well, apply to many or most waterbase printers. For example, you have previously and in this instance, said
A, a 5kMH is far superior in every way).
That's false. It's false simply because you, do not run every 5KMH in the industry under every scenario. Trust me, there are many extreme differences in shop to shop and their particular needs. That's obvious, because there are shops out there that do print waterbase day in and day out, doing high end sim process...and have ditched their MH. Whatever it had been, 1, 3 5 I don't know. And you use for knowing that it's not (as good) as your 5kmh. No issues. So I'm say'n, (it does work for PP and it does work (for waterbase printers). Your whole statement about the 5kmh being FAR superior, seems null and void.
And I'll wager or rather or come right out and say, You probably know twice what I do about exposing screens, cuz you live it and especially (in your shop). Me, I was just there at various shops long enough to do it for 1-2 days per week. So don't get me wrong. I'm not pushing M&R and I'm not saying "I know more than you"...but I know what is being done and had been done on these machines with all different emulsions...despite what you experienced in your shop. An I'll say this. To give a blanket statement as if it's fact that it pertains to ALL shops who use any Diazo, is not a good or accurate statement.
I'll also say, that I'd rather have a 5K MH (for me...and for what I would want to do) if I had my own shop and the $ to buy either, but then again, I'd also prefer to be a millionaire or at least own my own shop.
My comment about the I-Image working next to a 5k MH doing 4 up, (did not) and does not say that it was faster than. That wasn't the point of mentioning the 5k.
I said "that 5k MH was doing 4 screens at a time that exposed at 8 min on 110 mesh's whilst thy were clicking away on the I-Image". Actually, it was longer than just 8, but I rounded. I've seen that happen twice. Two different shops. The one shop did 8 screens at a time. A whole wall, but it was for a longer exposure time. That shop had already had three different brands of DTS machines sitting right there (partially in use) whilst I installed an STEII. They were a big and busy shop. Now, I get that. I get why to use a 5k and expose 4 or 8 screens up at a time. I don't have anything against an 8 min exposure time (for 4 screens). That's good stuff.
One more thing. I did't quite understand the one point you made about there professionals.
M&R, professionals they are, confirmed the times using same mesh/emulsion/coating to make sure there wasn't something off with the unit or with our process.
. If you are saying that M&R sent in some people to see what the dillio was, (running exp test, coating etc), than I am still not convinced.
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My comment about the I-Image working next to a 5k MH doing 4 up, (did not) and does not say that it was faster than. That wasn't the point of mentioning the 5k.
I said "that 5k MH was doing 4 screens at a time that exposed at 8 min on 110 mesh's whilst thy were clicking away on the I-Image". Actually, it was longer than just 8, but I rounded. I've seen that happen twice. Two different shops. The one shop did 8 screens at a time. A whole wall, but it was for a longer exposure time. That shop had already had three different brands of DTS machines sitting right there (partially in use) whilst I installed an STEII. They were a big and busy shop. Now, I get that. I get why to use a 5k and expose 4 or 8 screens up at a time. I don't have anything against an 8 min exposure time (for 4 screens). That's good stuff.
I would be PISSED if it took 8 min to expose screens!!!
We actually did 4 up on the wall with the 5k unit. It is still semi set up for our all over screens. It has been a while and I'm not at work so I don't have the light units we have recorded. I want to say for us it was around 50-85 light units(roughly 4 min) to expose a set of screens. The high end was a 135S mesh coated 2/1, low end was the 380 coated 1/1.
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My comment about the I-Image working next to a 5k MH doing 4 up, (did not) and does not say that it was faster than. That wasn't the point of mentioning the 5k.
I said "that 5k MH was doing 4 screens at a time that exposed at 8 min on 110 mesh's whilst thy were clicking away on the I-Image". Actually, it was longer than just 8, but I rounded. I've seen that happen twice. Two different shops. The one shop did 8 screens at a time. A whole wall, but it was for a longer exposure time. That shop had already had three different brands of DTS machines sitting right there (partially in use) whilst I installed an STEII. They were a big and busy shop. Now, I get that. I get why to use a 5k and expose 4 or 8 screens up at a time. I don't have anything against an 8 min exposure time (for 4 screens). That's good stuff.
I would be PISSED if it took 8 min to expose screens!!!
We actually did 4 up on the wall with the 5k unit. It is still semi set up for our all over screens. It has been a while and I'm not at work so I don't have the light units we have recorded. I want to say for us it was around 50-85 light units(roughly 4 min) to expose a set of screens. The high end was a 135S mesh coated 2/1, low end was the 380 coated 1/1.
Well, as you know, yes, that's one exposure for 8 min, but that's like 4 screens at 2 min each. So not "that horrible" I guess it decreases as you pull back further to encompass all screens for a good exposure all over each screen. I'm sure their bulb just needed replaced.
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We are still dialing in our new Starlight but with diazo emulsion we are more in the 15 to 20 second range. More than that we are seriously pinching detail but we're still in the test phases seeing if we get breakdown on press.
BTW - Chromaline CP Tex, using CTS rails, no glass.
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This may help since it's Murakami but for SP-1400 with no glass we do:
28 sec for 225S mesh
40 sec for 150S mesh
Coated 1/1 sharp edge.
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Haha, ok Dan aside from power consumption and bulb life, tell me in what way LED exposure is superior to MH, for any shop. ;)
To clarify, my comment about M&R being pros was to be taken literally. We have longer times than they say you should have for the unit and they took the time to test and confirm that. If you use our emulsions and fully expose your screens the results should be about the same on any starlight unit. That is not a shop to shop thing, and that's according to them, not me.
I'm ok with it all but I miss the MH is all I'm saying. Someday the LED units will get there I'm sure.
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Haha, ok Dan aside from power consumption and bulb life, tell me in what way LED exposure is superior to MH, for any shop. ;)
To clarify, my comment about M&R being pros was to be taken literally. We have longer times than they say you should have for the unit and they took the time to test and confirm that. If you use our emulsions and fully expose your screens the results should be about the same on any starlight unit. That is not a shop to shop thing, and that's according to them, not me.
I'm ok with it all but I miss the MH is all I'm saying. Someday the LED units will get there I'm sure.
The first obvious variable that comes to my mind on this statement is that some shops may use the same emulsions, but either not the same mesh counts, or coat to the same EOM. I see more than one post in which someone coats the same mesh thinner (with an insufficient EOM) for detailed work, something that could bite them as it also introduces the "jaggies" from the mesh pattern
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Totally Frog. It does make it hard to swap notes for sure.
What M&R did was go to the trouble to use our same mesh, emulsion, coating (even down to the coater I believe). That was what I wanted to clarify since Dan asked- they really dug into it and the times, within a little variance, are repeatable.
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Hi,
5 Sec Vacum and 60 Sec exposure for White Mesh 155, 2;2 Murakami SP emulsion. The emulsion comes right off when I spray with high power water pressure. I can actually pill the emulsion row by row with the water. Is this issue under expose? The graphic could wash out within few second. Then the graphic begin to wash out as well.
Thanks.
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Under.
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Hi,
5 Sec Vacum and 60 Sec exposure for White Mesh 155, 2;2 Murakami SP emulsion. The emulsion comes right off when I spray with high power water pressure. I can actually pill the emulsion row by row with the water. Is this issue under expose? The graphic could wash out within few second. Then the graphic begin to wash out as well.
Thanks.
get yourself an exposure calculator...
gut feeling is to double your exposure time and try again.
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Glad to see much response :) Murakami Japan gave me that 60 sec mark as starting point. They do not have M&R starlight so they throw that 60 sec number base on the exposure unit they have in their office.
Ruby, this goes back to what Murakami told you. 60 seconds is your starting point for testing. In this context, trying a range of half of that to twice that. 30 sec - 120 sec.
If you don't have an exposure calculator, or if you want to see the results on the actual media you use for your "films", do a manual step-wedge test.
Murakami themselves give this same advice and offer these instructions on how to run a test. (http://murakamiscreen.com/wp-content/uploads/2012/07/Step-Test-Instructions.pdf)
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Thanks for the reply :) I'll coat several screen today and try again. I do have exposure calculator from Chromaline.
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I just bought exposure calculator and it should be able to help me dial in the expose time. Product ship all the way from UK lol.
I did expose 2 screens today.
Both screens was coated 2;2
110 mesh exposed 75 sec
155 mesh exposed 75 sec
110 mesh couldn't hold fine detail. It washes out with water.
155 mesh hold detail very well. All the hair thickness detail was there.
When the screen couldn't hold detail, this is because under exposed? How do I know if I over exposed? This is really dumb question but I think a lot noob have this in their mind ><
Should I increase the exposure time to 90 sec for 110 mesh?
Thanks.
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I just bought exposure calculator and it should be able to help me dial in the expose time. Product ship all the way from UK lol.
I did expose 2 screens today.
Both screens was coated 2;2
110 mesh exposed 75 sec
155 mesh exposed 75 sec
110 mesh couldn't hold fine detail. It washes out with water.
155 mesh hold detail very well. All the hair thickness detail was there.
When the screen couldn't hold detail, this is because under exposed? How do I know if I over exposed? This is really dumb question but I think a lot noob have this in their mind ><
Should I increase the exposure time to 90 sec for 110 mesh?
Thanks.
Ruby, if you are experimenting while waiting for your calculator, do a damn step wedge test like I linked to way back! It's the only way to accurately determine the correct times for each of your mesh counts. Why are you resisting this standard procedure, newbie or not? Do exposures from less than 60 seconds to 120 seconds (or more).here's the link again. http://murakamiscreen.com/wp-content/uploads/2012/07/Step-Test-Instructions.pdf (http://murakamiscreen.com/wp-content/uploads/2012/07/Step-Test-Instructions.pdf)
You should see your underexposed areas wash out prematurely and your overexposed closing in and not washing out.
You'll probably see actual stripes showing the "steps", and you should see the sweet spot that rinsed out fine and also held your detail. You will notice that higher mesh counts usually expose faster, and you will find that white exposes faster than the yellow and orange and other colored meshes you may come across. Make sure to document your findings carefully.
The calculator does these "steps" for you in one long exposure with different tints letting light in in the equivalent of different times.
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I'll give it a try tomorow :)
Thanks for the link.
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Hello Rubsky and all the other great posts here. We have been doing tests at various facilities using the Starlight or STE and here are some tips that will help>
Coating: Keep coating thin. 1:1 dull maximum, 1:2 sharp a little less emulsion, 1:1 sharp even less emulsion. This is with an American style coater with a thick 1/8th inch edge and a thin 1/16th inch edge. In Japan we use much sharper scoop coaters than the US so that is why they recommend more coats. So the edge profile should be looked at when talking about the number of coats since different coaters, speed and angle can all yield very different emulsion thicknesses.
Exposure: Humidity is the main reason times from one shop to another could be different, along with different thicknesses of emulsion coated, different scoop coaters, etc. So times can vary shop to shop. I can shoot faster in SoCal on a hot offshore day when humidity is at 6% than I can on a rainy day with humidity at 100%. We don't see the differences much on a Metal Halide since it has a wider latitude or window of good exposures. But on an LED with shorter times, the window for a good strong expsosure and details can be much more narrow. Humidity or the moisture in the air is absorbed by emulsions, like a sponge, and it affects exposure. Also dry your screens well before exposure. Drying overnight, or using a dehumidifier is recommmended in your screen room. Separate the sink, reclaiming and developing from your screen storage area. It will be hard to dial in the correct exposure if the humidity jumps up and down due to reclaiming, wet reclaimed screens, or overspray entering your screen room area.
LED vs Metal Halide this is one of user preference. I have a new appreciation for the productivity of LED and if you don't overcoat the emulsion they work very well and have cost/production benefits. They do produce strong screens, but a pure photopolymer emulsion like HVP or Murakami T9 have an advantage with post exposure. This really helps with discharge, water base or HSA printing to obtain a 'stronger' screen through post exposure.
Step Test, Hardness Scale, Exposure Calculator for LED the Step test is the way to go. The 2 pieces of film used in a calculator will block a substantial amount of LED light. My tests here in the lab gave higher exposure times than my step test. The step test method did help get details and durability. Using a hardness scale with the resulting times and hitting 6-7 will validate the time.
Rubsky: Use Murakami MS-Degreaser - this is our go to product for good emulsion adhesion. If exposed well the emulsion will hold better with a good degreaser. Dishwashing soap should be avoided due to oils in there to prevent dry hands.
Don't be surprised at the softness of the exposure on an LED. Once dried it will print plastisol fine. For waterbase and discharge try Murakami T9. You can post expose in sun, or on a 5k MH, or back on the LED itself for post exposure. Post expose the squeegee side. Pure photopolmers and LED allows for post exposure. M&R's new Gemini LED exposure unit does exposure on one side and post exposure on both sides very efficiently.
Rubsky you mentioned SP emulsion, This is SP-1400? I have many, many SP emulsions, please clarify.
Admiral's times of
28 seconds for 225S
40 for 150S
for SP1400 match closely to my tests here. Note he coated 1:1 sharp. Less coating is better for LED exposure. If you coat more or use a thick edge your times will go up. I would use these times on halftone work, for vector I would bump up exposure by 5-10 seconds just to cook it more.
Bake the Cake, if you dry well, expose as much as you can while still retaining details, dry well in a hot box or the sun, you will have baked the cake and have a durable screen.
I will be presenting at Totally T-shirts in April showing how to use LED with Murakami T9 to print any ink without hardeners. Contact SGIA for reservations.
Al