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screen printing => Screen Making => Topic started by: Maff on January 27, 2016, 12:03:21 PM
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The quick question is this,
Do you change your screen making process with S-mesh screens, as apposed to how you would for regular t-mesh??
and do you find they are much more sensitive to all the different elements and conditions for proper screen making?
The longer story is this,
So, I had been using regular T-mesh for over 10 years with fine results.
And then I started reading here about S-mesh/ thin thread mesh technology and how they could be an added benefit where t-mesh under performs.
I was excited to jump in and got my first round of Static S-mesh screens last year.
Right out of the gate we could not get them to expose properly.
My control is this. Every time we make and process screens we are using both t-mesh and S-mesh at the same time. Same emulsion, coating, exposure, reclaim, dehaze... everything is the same for both.
The main Problem I am having is getting a good deal of slime on the inside of the screen after exposing and washing out and sometimes we will also loose halftone details as well. At first the Stauffer strip calculator would just totally blow out. We adjusted our exposure times quite a bit longer to the point where if we were careful enough we could get the image to expose, but still having slime on the inside and still not always getting our halftone details to stay.
My first though is that it seemed like the emulsion just wasn't grabbing this mesh.
I called Murakami, spoke with Al, went over all the basic stuff... everything should be the same. He recommended we change the bulb in our Exposure unit... it was old, but our t-mesh screens expose fine... I changed it anyways just to cancel that out. We have a 850W MH Nuarc exposure unit.
Called our supplier of the screens (spot color supply) to pick their brain and same responses... all should be the same. They recommended Direct Prep-2... tried that with no noticeable difference.
(customer service was great from both BTW, very patient and took their time to go through it with me. :)
Tried changing emulsions, we use photopolymers, originally Chromaline WR... Switched over to Saati PHU and got the same results... (however, we really like this emulsion better with our regular t mesh and have been sticking with it)
We did have slightly better results with thinner coats of emulsion. (I don't have an EOM gauge yet, but have been going off of trials and experience)
We have our coated screens in a decently well climate controlled environment with a thermometer and humidity gauge. We did notice slightly better exposure results when the screen booth temp is higher than 70 degrees and humidity % is in the 20s.
When we get the screens to expose good enough and get them out on press... They have printed really awesome!!! ;D and I really want to make them work in our shop dam it! we've been struggling with this for like 6 months now >:(.
Also, if they get to press, the screens aren't breaking down, but we have been post exposing just to make sure and especially since we do a fair amount of waterbase and discharge printing
Jvanick just mentioned that he uses Direct Prep-1 on the first round in the shop. We were told that it wasn't a good idea because it could harm the mesh... but honestly it kind of makes sense in the results I'm seeing, maybe it would give the mesh more grip on the emulsion...
Anyways, this is where I'm at. Any other ideas would be greatly appreciated.
Thanks again everyone!!!!
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I'm a capillary film user and I have to hit them with a good scrubbing of mesh abrader. I hate doing it, but it's the only way I can make it work. After the first couple of rounds with a new screen they coat/expose like normal. It was pretty stressful for us as we swapped all of our screens over and couldn't get anyyhing to expose. I'm curious to see what others have to say. I just assumed it was because I'm the odd cap film user.
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I'm a capillary film user and I have to hit them with a good scrubbing of mesh abrader. I hate doing it, but it's the only way I can make it work. After the first couple of rounds with a new screen they coat/expose like normal. It was pretty stressful for us as we swapped all of our screens over and couldn't get anyyhing to expose. I'm curious to see what others have to say. I just assumed it was because I'm the odd cap film user.
yeah that's actually what is making me go nuts here since we still have our t-mesh in the same rotation and they work fine... if I didn't have them, id really be going crazy...
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if you coat the T and S the same, S will have almost twice the thickness of the emulsion and you will have to increase your exposure times. Keep burning until there is no slime on the other side.
pierre
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Pierre is correct-
More open area allows more emulsion to flow out of trough with s-mesh.
I couldn't believe how the rz value changed with s-mesh too. Smooth as a baby's butt.
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yea I went from 2/1 with round side of an old coater on standard mesh to 1/1 sharp with monster max and s mesh.
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if you coat the T and S the same, S will have almost twice the thickness of the emulsion and you will have to increase your exposure times. Keep burning until there is no slime on the other side.
pierre
Right. Usually we would coat 1x1 with the round side. We have been trying 1x1 sharp side on 150s with slightly better results but still getting some slime.
But we did also try increasing our exposure, in our initially test we doubled our exposure times and still getting some slime.
Maybe the screens weren't dry enough? we try to give them a good day of dry time after coat.
Although we have our screens in a decently controlled environment I've noticed they are still affected by our weather... if it's super hot and humid in the summer we were fighting to keep the humidity down in the screen booth and also since it's been a lot colder we recently bumped up the heat... There was another topic recently discussing the colder weather and exposure times.
It all made me wonder if the s-mesh are just more sensitive... or am I just realizing that screen making in general needs to be more precise and conscious part of the process... everything with our Tmesh was easy... rarely any issues.
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if you coat the T and S the same, S will have almost twice the thickness of the emulsion and you will have to increase your exposure times. Keep burning until there is no slime on the other side.
pierre
Right. Usually we would coat 1x1 with the round side. We have been trying 1x1 sharp side on 150s with slightly better results but still getting some slime.
But we did also try increasing our exposure, in our initially test we doubled our exposure times and still getting some slime.
Maybe the screens weren't dry enough? we try to give them a good day of dry time after coat.
Although we have our screens in a decently controlled environment I've noticed they are still affected by our weather... if it's super hot and humid in the summer we were fighting to keep the humidity down in the screen booth and also since it's been a lot colder we recently bumped up the heat... There was another topic recently discussing the colder weather and exposure times.
It all made me wonder if the s-mesh are just more sensitive... or am I just realizing that screen making in general needs to be more precise and conscious part of the process... everything with our Tmesh was easy... rarely any issues.
how long are your exposure times? I would expect a 3min +, possibly 5 with an 850W and 150S.
pierre
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When we switched from T to S mesh, we had all sorts of issues, and it took us a LONG time to get things sorted out. At first we blamed the emulsion, and in a way it IS an emulsion issue, but more due to how the emulsion interacts with the mesh.
The intermediate story is long due to all of our testing... for that, I apologize.
To start the story:
when we switched to S-Mesh we started having edge breakdown and wear issues right out of the gate, sometimes even breaking down 5-10 shirts in to the run. you could actually hear the screen 'crackling'... We had changed to S-mesh in the winter, so the first thought was the SP1400 we were running was prone to issues in low humidity so Murakami had us try SP1400-W (a winter blend for SP1400)... the issues continued, not quite as bad, but still there, we started taping on the top of the screen well into the squeegee path... again, we'd still have issues (anybody who's met Tiffany know's that she's a tape nazi (no tape for you!) and she was complaining about all the tape... and heck sometimes the cracking would follow the tape into the rest of the image area, especially on long runs.
Somewhere around this time I started thinking that the Starlight didn't have the 'punch' to get through the screens successfully, this was totally incorrect, as the screens are being initially exposed correctly (solid 7 step), when we were having issues, we kept on adding time as well thinking more exposure would help (it didn't)
* we started playing with different types & brands of emulsions with differing results, but we still had wierd issues...
We did sun exposures with several different emulsions to prove out that the initial exposure wasn't the issue...
Then we switched over to Saati PHU-2, had the same issues, and started some major in-depth testing in the shop.
1. We got the exposure times dialed in better (they were concerned as we were over-exposing our screens, by 2 steps on the strip) -- better detail after that, but no better results on press.
2. We found that a 1/1 on the S-mesh (even 225S!) was resulting in 50% or more EOM. We did a ton of testing here, until we finally found that 1 coat on the shirt side was all that was needed to achieve a repeatable 20%-ish EOM. -- no better results on press.
3. We started post exposing... tried Starlight, saati 300W LED, and sun post exposure. While the Saati 300W and Sun post exposure seems to result in better discharge/wb/hsa screens, for any plastisol work, there was no better results on press.
4. We started using Saati DirectPrep2 on our screens... no fish eyes, pinholes, water marks, anything after that, and the emulsion coats even smoother... but no better results on press.
*** It's important to note that through ALL of this, our older T-thread mesh screens were having NO issues. This should have been a sign, but really with everything else going on, it didn't click.
FINALLY after at least a month of testing... Saati has us try Direct Prep 1 which is a light mesh abrader... at first I questioned this as "nobody needs mesh abraders anymore" seems to be the advice of everybody.
The first set of screens onto the press showed an immediate improvement, and since then, we've had no issues.
After talking with Saati, we think the issue is a emulsion adhesion to the smooth smesh, and with the fact that there's less thread diameter for the emulsion to 'grab' onto, we need to 'rough' the mesh up a touch with the abrader to get better mesh adhesion, and that was the issue...
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if you coat the T and S the same, S will have almost twice the thickness of the emulsion and you will have to increase your exposure times. Keep burning until there is no slime on the other side.
pierre
Right. Usually we would coat 1x1 with the round side. We have been trying 1x1 sharp side on 150s with slightly better results but still getting some slime.
But we did also try increasing our exposure, in our initially test we doubled our exposure times and still getting some slime.
Maybe the screens weren't dry enough? we try to give them a good day of dry time after coat.
Although we have our screens in a decently controlled environment I've noticed they are still affected by our weather... if it's super hot and humid in the summer we were fighting to keep the humidity down in the screen booth and also since it's been a lot colder we recently bumped up the heat... There was another topic recently discussing the colder weather and exposure times.
It all made me wonder if the s-mesh are just more sensitive... or am I just realizing that screen making in general needs to be more precise and conscious part of the process... everything with our Tmesh was easy... rarely any issues.
how long are your exposure times? I would expect a 3min +, possibly 5 with an 850W and 150S.
pierre
Thanks everyone,
Piere, No we're much less. With PHU we've been under a minute... but our T-mesh hits a solid 7 on the Stauffer strip every time.
Could the layer of emulsion be that much thicker on a S-Mesh? twice as much? Like 150s vs 156t for example...
Also, what do you think about abrading s-mesh... anybody else doing that?
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First:
What emulsion are you using. And what exposure times do you have for your standard 150 mesh?
For my Nuarc 3140 1k Metal Halide bulb. A 150/54 murakami mesh panel coated 1x2 with a monster max coater using Saati PHU with up to 30% EOM I expose for about 90 light units. This gives me a solid step 7 with a stoufer strip. It also holds awesome detail.
For a 150 S mesh from Murakami I need to expose for about 130 light units. My eom is around 50%. This gives me a relatively solid step 7 on the stoufer strip. I do need to be more careful with thin lines and finer detail than I do with standard mesh. This is simply due to the lower thread area/solid area for the emulsion to grab onto.
Note on emulsion hardness:
The FIRMER an emulsion is, the more you will see these finer areas hold its image shape. Simply because the emulsion is more rigid.
The SOFTER an emulsion is, the more these fine areas will wash away even with proper exposure/over exposure
***BIG NOTE FOR ALL THIN THREAD MESHES****
Because you have less surface area/thread area for the emulsion to grab onto, it is easier for the emulsion to release on the stoufer strip. Thereby giving you an inaccurate reading about "full" exposure. You can easily end up with a solid step 5 or 6 when it should be 7.
A lot of this is determined by how long the screen HAS BEEN ABSORBING/SOAKING up water. The more chance it has to soak up water, the easier it is to release.
These observations are what happens in my shop, with my equipment. Your mileage may vary :)
As for direct prep:
It abraids the mesh making for better mechanical abrasion.
The reason why you see cracking on water resistant emulsions is do to the emulsion DELAMINATING from the mesh under high pressure.
Because of the better mechanical adhesion you see less delamination of the emulsion.
Delamination/cracking typically happens with very dry screens and occasionally screens with a thicker emulsion coat but I don't know the nuances of why.... There are apparently other reasons as well, which I also am not currently aware of.
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Also, what do you think about abrading s-mesh... anybody else doing that?
According to some here, as Martha Stewart may say, "it's a good thing", but I cringe a little.
The knock on physically abrading mesh to increase "tooth" is that it weakens the mesh. The biggest caution on S mesh is that it's more fragile to begin with.
In general, most have gotten away from abraders with emulsion due to it's characteristic of encapsulating the mesh, but may still use it with capillary film (and older direct and indirect stencil films) which does not tend to do the same.
I am really curious about this.
Let's see how mesh lifespan is affected, if at all.
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When we switched from T to S mesh, we had all sorts of issues, and it took us a LONG time to get things sorted out. At first we blamed the emulsion, and in a way it IS an emulsion issue, but more due to how the emulsion interacts with the mesh.
The intermediate story is long due to all of our testing... for that, I apologize.
To start the story:
when we switched to S-Mesh we started having edge breakdown and wear issues right out of the gate, sometimes even breaking down 5-10 shirts in to the run. you could actually hear the screen 'crackling'... We had changed to S-mesh in the winter, so the first thought was the SP1400 we were running was prone to issues in low humidity so Murakami had us try SP1400-W (a winter blend for SP1400)... the issues continued, not quite as bad, but still there, we started taping on the top of the screen well into the squeegee path... again, we'd still have issues (anybody who's met Tiffany know's that she's a tape nazi (no tape for you!) and she was complaining about all the tape... and heck sometimes the cracking would follow the tape into the rest of the image area, especially on long runs.
Somewhere around this time I started thinking that the Starlight didn't have the 'punch' to get through the screens successfully, this was totally incorrect, as the screens are being initially exposed correctly (solid 7 step), when we were having issues, we kept on adding time as well thinking more exposure would help (it didn't)
* we started playing with different types & brands of emulsions with differing results, but we still had wierd issues...
We did sun exposures with several different emulsions to prove out that the initial exposure wasn't the issue...
Then we switched over to Saati PHU-2, had the same issues, and started some major in-depth testing in the shop.
1. We got the exposure times dialed in better (they were concerned as we were over-exposing our screens, by 2 steps on the strip) -- better detail after that, but no better results on press.
2. We found that a 1/1 on the S-mesh (even 225S!) was resulting in 50% or more EOM. We did a ton of testing here, until we finally found that 1 coat on the shirt side was all that was needed to achieve a repeatable 20%-ish EOM. -- no better results on press.
3. We started post exposing... tried Starlight, saati 300W LED, and sun post exposure. While the Saati 300W and Sun post exposure seems to result in better discharge/wb/hsa screens, for any plastisol work, there was no better results on press.
4. We started using Saati DirectPrep2 on our screens... no fish eyes, pinholes, water marks, anything after that, and the emulsion coats even smoother... but no better results on press.
*** It's important to note that through ALL of this, our older T-thread mesh screens were having NO issues. This should have been a sign, but really with everything else going on, it didn't click.
FINALLY after at least a month of testing... Saati has us try Direct Prep 1 which is a light mesh abrader... at first I questioned this as "nobody needs mesh abraders anymore" seems to be the advice of everybody.
The first set of screens onto the press showed an immediate improvement, and since then, we've had no issues.
After talking with Saati, we think the issue is a emulsion adhesion to the smooth smesh, and with the fact that there's less thread diameter for the emulsion to 'grab' onto, we need to 'rough' the mesh up a touch with the abrader to get better mesh adhesion, and that was the issue...
Thanks Jvanik! Wow You went through it hard!
Your situation is sounding very similar to mine.
So did you only use the Direct Prep-1, one time or multiple times per screen?
I think I'll give the direct prep-1 a try. It makes sense to me... but its strange that no one else has made much mention... maybe there is another way around it?
And I'm also going to need to do more testing with exposure time and EOM and keep close track of my results... at the end i'll at the very least have a much better understanding of the finest details.
Now I just need to get myself an EOM gauge... any suggestions?
Thanks everyone!!!
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Just once at the beginning of new mesh seems to be all it takes
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What emulsion are you using. And what exposure times do you have for your standard 150 mesh?
Saati PHU and we are under a minute... but our stauffer strip reads 7 on T-mesh and always has... but this is way off compared to what everyone else here is saying, so maybe i need to adjust this.
***BIG NOTE FOR ALL THIN THREAD MESHES****
Because you have less surface area/thread area for the emulsion to grab onto, it is easier for the emulsion to release on the stoufer strip. Thereby giving you an inaccurate reading about "full" exposure. You can easily end up with a solid step 5 or 6 when it should be 7.
A lot of this is determined by how long the screen HAS BEEN ABSORBING/SOAKING up water. The more chance it has to soak up water, the easier it is to release.
Yeah I found it very strange how the stuaffer strip acts so differently with the S-Mesh
so after exposure, how long do you keep it in the developing tank before rinsing out?
Typically ours sit in the water for about 1-2 min
thanks again!!
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And I'm also going to need to do more testing with exposure time and EOM and keep close track of my results... at the end i'll at the very least have a much better understanding of the finest details.
Now I just need to get myself an EOM gauge... any suggestions?
I use one of these:
http://www.ebay.com/itm/New-CEM-DT-156-Paint-Coating-Thickness-Gauge-Tester-F-NF-Probes-1250-Im-/221993822236?hash=item33afdce81c:g:a18AAOxy4dNSxTRB (http://www.ebay.com/itm/New-CEM-DT-156-Paint-Coating-Thickness-Gauge-Tester-F-NF-Probes-1250-Im-/221993822236?hash=item33afdce81c:g:a18AAOxy4dNSxTRB)
for my emulsion testing, I use the following document:
https://docs.google.com/spreadsheets/d/1bsqE6POiBiCCztbQZlCZIOG_TlYNbZRtJ6_x7aTcShI/edit?usp=sharing (https://docs.google.com/spreadsheets/d/1bsqE6POiBiCCztbQZlCZIOG_TlYNbZRtJ6_x7aTcShI/edit?usp=sharing)
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And I'm also going to need to do more testing with exposure time and EOM and keep close track of my results... at the end i'll at the very least have a much better understanding of the finest details.
Now I just need to get myself an EOM gauge... any suggestions?
I use one of these:
[url]http://www.ebay.com/itm/New-CEM-DT-156-Paint-Coating-Thickness-Gauge-Tester-F-NF-Probes-1250-Im-/221993822236?hash=item33afdce81c:g:a18AAOxy4dNSxTRB[/url] ([url]http://www.ebay.com/itm/New-CEM-DT-156-Paint-Coating-Thickness-Gauge-Tester-F-NF-Probes-1250-Im-/221993822236?hash=item33afdce81c:g:a18AAOxy4dNSxTRB[/url])
for my emulsion testing, I use the following document:
[url]https://docs.google.com/spreadsheets/d/1bsqE6POiBiCCztbQZlCZIOG_TlYNbZRtJ6_x7aTcShI/edit?usp=sharing[/url] ([url]https://docs.google.com/spreadsheets/d/1bsqE6POiBiCCztbQZlCZIOG_TlYNbZRtJ6_x7aTcShI/edit?usp=sharing[/url])
Awesome Thanks!!
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if you coat the T and S the same, S will have almost twice the thickness of the emulsion and you will have to increase your exposure times. Keep burning until there is no slime on the other side.
pierre
Right. Usually we would coat 1x1 with the round side. We have been trying 1x1 sharp side on 150s with slightly better results but still getting some slime.
But we did also try increasing our exposure, in our initially test we doubled our exposure times and still getting some slime.
Maybe the screens weren't dry enough? we try to give them a good day of dry time after coat.
Although we have our screens in a decently controlled environment I've noticed they are still affected by our weather... if it's super hot and humid in the summer we were fighting to keep the humidity down in the screen booth and also since it's been a lot colder we recently bumped up the heat... There was another topic recently discussing the colder weather and exposure times.
It all made me wonder if the s-mesh are just more sensitive... or am I just realizing that screen making in general needs to be more precise and conscious part of the process... everything with our Tmesh was easy... rarely any issues.
how long are your exposure times? I would expect a 3min +, possibly 5 with an 850W and 150S.
pierre
Thanks everyone,
Piere, No we're much less. With PHU we've been under a minute... but our T-mesh hits a solid 7 on the Stauffer strip every time.
Could the layer of emulsion be that much thicker on a S-Mesh? twice as much? Like 150s vs 156t for example...
Also, what do you think about abrading s-mesh... anybody else doing that?
We use PHU and 150-S and on a 3K we are at 28 LTU or about 35 seconds. Screen is coated 1 on the shirt side and 2 on the squeegee side. EOM is way above 50% when we last checked. We land right around a 7 on the strip. Its a thick OEM but with a fast stroke and minimal off contact it deposits very little ink.
There is no need to abrade the mesh. We have have not had to abrade any of the S-Mesh that we use. We use 150-S, 180-S, 225-S, and 355-S with no issues at all.
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The cracking/delaminating seems to be most prevalent in the upper lattitudes/colder regions.
Cold and dry....
At least that has been my feedback from other people and manufacturers.
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there might also be a correlation with low(er) off-contact.
we haven't calibrated the press in a while, we are running a bit over 3/16 of off-contact...
but you're right about the dry air.. I noticed these issues WAY worse starting in the fall.
however, the mesh abrasion definitely resolved the issue for us... with out it, you could actually HEAR the emulsion starting to crack...
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Cap question with S mesh:
I use Ulano EZ film. Which is a 50 micron film. It is recommended for mesh counts of 86-196.They also make a 30 micron recommended for mesh counts of 230-419. I am using 150/48, 180/48, and 225/40.
For the 150 and 180 should I still be using the 50 micron film like I used with standard mesh? I assumed yes because with cap film it's the same thickness regardless. But reading this has me wondering if I should be using the 30 micron film instead.
Thoughts?
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Just a guick question, I haven't seen it brought up yet.
Is your T-mesh white or yellow?
Is your S-mesh white or yellow?
Just asking bc this will change times as well.
I agree with Pierre, coating S-mesh the same as T-mesh will give you almost twice as much EOM on the S over the T.
I have not done any abrading on mesh in over ten years. We typically just put them into shorter runs for the first few uses, and this is efficient work hardening for our mesh, S or T.
Our S-mesh burns for twice as long as our T-mesh, but it is also white vs yellow.
Murphy
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Just a guick question, I haven't seen it brought up yet.
Is your T-mesh white or yellow?
Is your S-mesh white or yellow?
Just asking bc this will change times as well.
I agree with Pierre, coating S-mesh the same as T-mesh will give you almost twice as much EOM on the S over the T.
I have not done any abrading on mesh in over ten years. We typically just put them into shorter runs for the first few uses, and this is efficient work hardening for our mesh, S or T.
Our S-mesh burns for twice as long as our T-mesh, but it is also white vs yellow.
Murphy
White T-mesh: 110, 123, 156
Yellow T-mesh: 230, 280, 305
Yellow S-Mesh: 150s, 180s, 225s
All have been calculated separately and I have different settings for each mesh on the exposure unit.
Every once and while also through the stauffer strip on there to make sure things are consistent.
I definitely think that I need to pay closer attention to the EOM. I just ordered an EOM gauge so I can start to find out precisely what that is per screen.
with the next batch of screens I get in I'm going to use direct prep 1 on just a couple and see if it makes any noticeable difference.
Once i get some new results I will check back in and post them.
thanks again for all of the advise!
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with the next batch of screens I get in I'm going to use direct prep 1 on just a couple and see if it makes any noticeable difference.
We may still still need to figure out if all of that product's ingredients' effects are what changed your results, or just the detergent, the wetting agent, or the abrader
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with the next batch of screens I get in I'm going to use direct prep 1 on just a couple and see if it makes any noticeable difference.
We may still still need to figure out if all of that product's ingredients' effects are what changed your results, or just the detergent, the wetting agent, or the abrader
I was told that DirectPrep1 is just an abrader... DirectPrep2 is the wetting agent/detergent...
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http://www.saati.com/images/chemicals/products/direct-prep-1.pdf (http://www.saati.com/images/chemicals/products/direct-prep-1.pdf)
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[url]http://www.saati.com/images/chemicals/products/direct-prep-1.pdf[/url] ([url]http://www.saati.com/images/chemicals/products/direct-prep-1.pdf[/url])
Interesting. . They have me using the dp2 after the dp1.. it's only once during the screen process so it really doesn't bug me.
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with the next batch of screens I get in I'm going to use direct prep 1 on just a couple and see if it makes any noticeable difference.
We may still still need to figure out if all of that product's ingredients' effects are what changed your results, or just the detergent, the wetting agent, or the abrader
True, that would skew the test results... But aren't most abraders also degreasers anyways?
Either way... I have already been using the Direct Prep-2 and haven't seen any significant changes in my situation.
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with the next batch of screens I get in I'm going to use direct prep 1 on just a couple and see if it makes any noticeable difference.
We may still still need to figure out if all of that product's ingredients' effects are what changed your results, or just the detergent, the wetting agent, or the abrader
True, that would skew the test results... But aren't most abraders also degreasers anyways?
Either way... I have already been using the Direct Prep-2 and haven't seen any significant changes in my situation.
Agreed... we had no difference with dp2 either... it was the dp1 that made things work for us.
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True, that would skew the test results... But aren't most abraders also degreasers anyways?
The abrader I used back in the day before I learned better, was Ulano Microgrit 2, just a black powder, probably carborundum like a sharpening stone. They also sell it as a gel mixed with a degreaser, Unogel 23.
btw, years ago, I ground an old porthole into a telescope mirror, and used varying coarseness versions of similar grit to get the original rough shape.
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True, that would skew the test results... But aren't most abraders also degreasers anyways?
The abrader I used back in the day before I learned better, was Ulano Microgrit 2, just a black powder, probably carborundum like a sharpening stone. They also sell it as a gel mixed with a degreaser, Unogel 23.
btw, years ago, I ground an old porthole into a telescope mirror, and used varying coarseness versions of similar grit to get the original rough shape.
WHAT??? ???.... That sounds like something a old pirate would say.
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Boy that detour was certainly beyond the Stratosphere. Pun intended.
You'll get the exposure right, just takes a few tries.
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The abrader I used back in the day before I learned better, was Ulano Microgrit 2, just a black powder, probably carborundum like a sharpening stone. They also sell it as a gel mixed with a degreaser, Unogel 23.
btw, years ago, I ground an old porthole into a telescope mirror, and used varying coarseness versions of similar grit to get the original rough shape.
WHAT??? ???.... That sounds like something a old pirate would say.
So would this. "Aaarrrrgghhh"!
Here comes one of those thread detours of which I am famous. (and defend as there is a logical progression) However, if discussion ventures far along this new path, it will need to get split, or perhaps moved to an entirely different forum, LOL!
Back when I lived in San Francisco in the late '70's, I was lucky enough to meet up with John Dobson who got me interested in telescopes and astronomy.
His mission was to bring the wonders of the heavens to everyone, and designed and helped us build cheap, but very effective reflector telescopes of his own design.
He had obtained a stash of old, thick, heavy 8" portholes perfect as mirror blanks for reasonably sized "light buckets". These were ground to the desired concave shape using various grits, ending with powders so fine that they polished, but still were abrasive enough to alter the shape and characteristics of the mirrors.
https://en.wikipedia.org/wiki/John_Dobson_(amateur_astronomer)
btw Gary, you are not imagining things. This post actually used to be above yours, LOL!
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Hello Everyone,
1. Pierre is correct, S mesh will yield a thicker EOM on S Mesh versus T mesh with the same coating techniques. With my emulsion I recommend 1:2 sharp for halftones, 1:1 dull edge for vector. Or 1:1 dull below 200, 1:2 sharp above 200.
110 vector: 20-25%
110 Detail lines: 10-15%
160 Vector 20%
160 45lpi Halftones 10-15%
225/40 Vector 15-20%
225/40 Halftones 7-12%
300/34 Halftones 6-7%
These numbers are all ball park. The point is too much EOM doesn't necessarily mean a better print. All depends on art, inks, and desired results. Your recipe may vary.
2. Too much EOM can cause cracking of emulsion when off contact is high. 1/8 is about all you need.
3. Round squeegee corners to prevent wear and tear along the edge. Very high momentary tension from squeegee edge to frame and emulsion flexing over a squeegee's point like corner, breakdown and cracking bound to happen, especially in winter.
4. As mentioned we make an SP1400 and an SP1400W. And as noted this happens more in the north where it is colder.
5. Relative Humidity vs Absolute Humidity is an interesting point I have run across. At 80 degrees 35% humidity is far more water in the air than at 35% with a temp of 40 degrees or less. The ability of the air to hold water is higher at high temps, and much lower at low temps even with the same humidity reading. So 35% at 80 is far more water in the air than 35% in 30 degree weather outside. Humidity readings need to be looked at differently depending on temperature. So my advice to those in winter conditions is to turn off your dehumidifier in winter, especially in cold screen rooms. Screens left in an unheated room overnight will be quite dry come morning in very cold conditions. Turning on the dehumidifier isn't going to help in winter conditions. I have even advised finding ways to raise humidity. 5 gallon pails of warm water, some wet screens to dry to get it up to 40-50%. Need someone to test this in winter conditions. It is working in a client in SoCal with SBQ now.
6. All Mesh counts have different EOM whether T or S. Each mesh has it's own recipe and is a good reason for larger shops to look into auto coaters where speed, pressure, and angle can be unique to each mesh and saved as a coating parameter. For hand coating every single shop, every single coater will have different EOM readings. Ambient temps in screen room also cause different viscosities in emulsion. 70-80 continuously helps. If your screen room is unheated then consider a warm box to keep the emulsion in. We used heating pads in our shop, under the emulsion and especially under 5 gallon pails, there are also commercial heaters you can wrap around 5 gallon pails to keep the temp constant.
7. Finally, what works in one shop may not apply in another. It may be correct, or ball park accurate. Each shop is unique in what coaters they choose, what emulsions they use, the temps and humidity, and not everything translates over 100%. Helpful advice, even mine, should be tested and calibrated in your shop and validated.
8. Be careful with paint thinner thickness gauges, their accuracy and signal strength can be inaccurate on thick emulsion stencils and mesh that paint never reaches. If they work, great, but validate with a gauge that can read up to 1000 microns accurately, which would be a 25/S with a mesh thickness of 456 microns and with emulsion approaches 1000 microns.
9. Abrading: NO, not advisable with S Mesh. Use MS-Degreaser for optimum results on Murakami S Mesh.
10. If using LED/Fluo Tubes post expose SBQ emulsion squeegee side. LED is the future, it is fast and easy. But some inks are super agressive and LED and Fluo to a certain degree don't completely cross link the squeegee side, 10-20 minutes in the sun in summer, or keep an old metal halide handy and hit for 2 minutes. This is only needed for discharge, HSA, and co-solvent inks. I recommend SBQ on LED's. It allows you to achieve a strong screen for tough inks via post exposure.
Al
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Hello Everyone,
1. Pierre is correct, S mesh will yield a thicker EOM on S Mesh versus T mesh with the same coating techniques. With my emulsion I recommend 1:2 sharp for halftones, 1:1 dull edge for vector. Or 1:1 dull below 200, 1:2 sharp above 200.
110 vector: 20-25%
110 Detail lines: 10-15%
160 Vector 20%
160 45lpi Halftones 10-15%
225/40 Vector 15-20%
225/40 Halftones 7-12%
300/34 Halftones 6-7%
These numbers are all ball park. The point is too much EOM doesn't necessarily mean a better print. All depends on art, inks, and desired results. Your recipe may vary.
2. Too much EOM can cause cracking of emulsion when off contact is high. 1/8 is about all you need.
3. Round squeegee corners to prevent wear and tear along the edge. Very high momentary tension from squeegee edge to frame and emulsion flexing over a squeegee's point like corner, breakdown and cracking bound to happen, especially in winter.
4. As mentioned we make an SP1400 and an SP1400W. And as noted this happens more in the north where it is colder.
5. Relative Humidity vs Absolute Humidity is an interesting point I have run across. At 80 degrees 35% humidity is far more water in the air than at 35% with a temp of 40 degrees or less. The ability of the air to hold water is higher at high temps, and much lower at low temps even with the same humidity reading. So 35% at 80 is far more water in the air than 35% in 30 degree weather outside. Humidity readings need to be looked at differently depending on temperature. So my advice to those in winter conditions is to turn off your dehumidifier in winter, especially in cold screen rooms. Screens left in an unheated room overnight will be quite dry come morning in very cold conditions. Turning on the dehumidifier isn't going to help in winter conditions. I have even advised finding ways to raise humidity. 5 gallon pails of warm water, some wet screens to dry to get it up to 40-50%. Need someone to test this in winter conditions. It is working in a client in SoCal with SBQ now.
6. All Mesh counts have different EOM whether T or S. Each mesh has it's own recipe and is a good reason for larger shops to look into auto coaters where speed, pressure, and angle can be unique to each mesh and saved as a coating parameter. For hand coating every single shop, every single coater will have different EOM readings. Ambient temps in screen room also cause different viscosities in emulsion. 70-80 continuously helps. If your screen room is unheated then consider a warm box to keep the emulsion in. We used heating pads in our shop, under the emulsion and especially under 5 gallon pails, there are also commercial heaters you can wrap around 5 gallon pails to keep the temp constant.
7. Finally, what works in one shop may not apply in another. It may be correct, or ball park accurate. Each shop is unique in what coaters they choose, what emulsions they use, the temps and humidity, and not everything translates over 100%. Helpful advice, even mine, should be tested and calibrated in your shop and validated.
8. Be careful with paint thinner thickness gauges, their accuracy and signal strength can be inaccurate on thick emulsion stencils and mesh that paint never reaches. If they work, great, but validate with a gauge that can read up to 1000 microns accurately, which would be a 25/S with a mesh thickness of 456 microns and with emulsion approaches 1000 microns.
9. Abrading: NO, not advisable with S Mesh. Use MS-Degreaser for optimum results on Murakami S Mesh.
10. If using LED/Fluo Tubes post expose SBQ emulsion squeegee side. LED is the future, it is fast and easy. But some inks are super agressive and LED and Fluo to a certain degree don't completely cross link the squeegee side, 10-20 minutes in the sun in summer, or keep an old metal halide handy and hit for 2 minutes. This is only needed for discharge, HSA, and co-solvent inks. I recommend SBQ on LED's. It allows you to achieve a strong screen for tough inks via post exposure.
Al
Thanks for all the great info Al !!!
The humidity vs high and low temperature is something I had not considered. Although I keep track of both in our screen room, I always just figured to try and keep the humidity under 30% and the temp above 65. So this is something I will be monitoring more closely.
I ordered the EOM (paint gauge) listed above and it is rated from 0 - 1250 microns, so that should do the trick.
Once I get that in i'll have a much more exact idea of our EOM and hopefully it will help get my screen results stabilized.
I'll be sure to post back with new results.
Thanks again!
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UPDATE:
We got ourselves a thickness gauge and have been keeping detailed track of our EOM for the past several weeks. Right away we noticed that our S-Mesh screens were at upwards of 40-50% EOM and our T-Mesh screens were 10% or less! This was coating 1/1 sharp side on S-mesh and 1/1 round side T-mesh, (except 280s and 305s which get the sharp side)
So, drastic difference there and likely to be the major factor in our exposure issues. It also makes sense how we were previously getting pretty short exposure times without any issues on our T-mesh, since there was barely any emulsion on them!
We are currently adjusting our coating methods in an effort to get our T-mesh EOM up and S-mesh EOM way down and hopefully get them more consistent with each other. And also adjusting our exposure times. Already we are seeing some better results, though we still need to get things better dialed in.
We also did try Direct prep 1 on a few new S-mesh screens, but really didn't notice any major difference… maybe just a little bit. But these screens are now permanently marked so we'll see how they work out over time.
Lastly we are also keeping close track of the temp and humidity. Our screens are kept in a decently controlled environment, but the weather this winter has been far from normal or consistent in the Northeast and it has been swinging our screen room some.
Thanks again everyone for all the help and input!!!