S-mesh screen making issues

[SoccerMom]

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.

[GaryG]

Boy that detour was certainly beyond the Stratosphere. Pun intended.

You'll get the exposure right, just takes a few tries.

[Frog]

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!

[ABuffington]

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

[Maff]

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!

[Maff]

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!!!