Emulsion Color and LED lights

[3Deep]

About a month ago I changed my old exposure unit to LED point light, now here is my question I've been using HXT emulsion for some time now with my old unit great emulsion but its blue/green and using it with my new unit I'm getting a slim on the print side of the screen at washout, which makes me bump the exposure way up.
So I switch emulsion to CCI other product VPR which is pink in color same high solids as HXT, but the VPR burns in 10 seconds all the way through vs HXT at over 2 minutes.  So does color have anything to do with using LED exposure lights? even the Ulano Orange which is orange in color works like a beast with LED or am I missing something here, my thinking is the color of the emulsion might play a big factor in LED exposure unit?

[blue moon]

About a month ago I changed my old exposure unit to LED point light, now here is my question I've been using HXT emulsion for some time now with my old unit great emulsion but its blue/green and using it with my new unit I'm getting a slim on the print side of the screen at washout, which makes me bump the exposure way up.
So I switch emulsion to CCI other product VPR which is pink in color same high solids as HXT, but the VPR burns in 10 seconds all the way through vs HXT at over 2 minutes.  So does color have anything to do with using LED exposure lights? even the Ulano Orange which is orange in color works like a beast with LED or am I missing something here, my thinking is the color of the emulsion might play a big factor in LED exposure unit?

from what I understand, color is not a factor. It has to do with the properties of the emulsion. Some are designed to expose faster and it's possible that's the reason why. Did you check on the spec sheet?

pierre

[RICK STEFANICK]

I think your going to need to do some exposure testing. moving to LED is usually not plug and play as your dramatically shortening your exposure window and different emulsions don't accommodate that  as well as others. Honestly the 2.5 second thing still throws me back. Even consistent coating is critical also

[3Deep]

@ P, yes I did check the specs on the CCI VPR and it is a fast exposing emulsion, that could be the reason, don't get me wrong I like the VPR but I also like my emulsion just a little darker I find it helps register screens better for me with seeing the image.
@ Rick 2.5 is some crazy fast exposure time, I'd think the screen would break down under long print runs, even at 11 seconds I'm doing now it still seems a little to long as the screen takes a little longer to wash out, but I'm afraid to expose any lower with full production.
You guys are right got lot's more testing to do until I locked in on a certain emulsion

[RICK STEFANICK]

@ P, yes I did check the specs on the CCI VPR and it is a fast exposing emulsion, that could be the reason, don't get me wrong I like the VPR but I also like my emulsion just a little darker I find it helps register screens better for me with seeing the image.
@ Rick 2.5 is some crazy fast exposure time, I'd think the screen would break down under long print runs, even at 11 seconds I'm doing now it still seems a little to long as the screen takes a little longer to wash out, but I'm afraid to expose any lower with full production.
You guys are right got lot's more testing to do until I locked in on a certain emulsion

We just did more tests and the Z1 is fine with the 5 seconds we are doing now off the digital. When we have to use film because of image size the times are longer. We realized under exoosure not from screen breakdown but the Eco rinse water discoloring and the residue left. Much much better now. There are shops out there shooting for 1 second. That just blows me away.

[Rockers]

I think your going to need to do some exposure testing. moving to LED is usually not plug and play as your dramatically shortening your exposure window and different emulsions don't accommodate that  as well as others. Honestly the 2.5 second thing still throws me back. Even consistent coating is critical also

That`s something I`m, still curious about how you do a good exposure test on a LED unit that`s converted for DTS, so no glass.

[Orion]

Check the viscosity of your HXT vs. VPR. If the VPR is of a higher viscosity that will result in a thicker EOM. Just a thought.

KIWO has digital files available for their DTS machines.

[Dottonedan]

I think your going to need to do some exposure testing. moving to LED is usually not plug and play as your dramatically shortening your exposure window and different emulsions don't accommodate that  as well as others. Honestly the 2.5 second thing still throws me back. Even consistent coating is critical also

That`s something I`m, still curious about how you do a good exposure test on a LED unit that`s converted for DTS, so no glass.

I've always used a digital file myself. But an emulsion Co would tell you "that's not 100% accurate".  You can use the stouffer exposure calculator (taped onto) the screen and it's been proven to work well that for DTS (no glass), you look for a step 6...and not a 7 like you would on glass.

[Maxie]

Why not use the 21 step wedge and get your exposure time right?

[ABuffington]

Emulsion color can help with LED, but is the color affecting the exposure more or is the light affecting exposure more?  More than likely the later.  While certain colors can help LED a little, the sensitizer used is what is hardening non image areas, the emulsion color is no where near as important as light spectral output, amplitude, and how it cross links the sensitizer.  An 8k Metal halide exposure at 42" with good black film imagery is the benchmark for high resolution durable screens, no post exposure needed, rarely needs hardeners with the right emulsion.  Halftones are much easier to capture.  Edge quality is sharper, but the industry trend is away from MH due to bulb costs. (Although I would argue it makes money with better production yields/per hour). LED does have speed advantages and can create good screens, but as mentioned the latitude of quality exposure of the emulsion is a narrow window often in tenths of a second.  So yes, you can get an image in a couple of seconds, but full exposure may be in the 17-19 sec range and need good black imagery.  In order of dmax and quality of resolution:  True Film at 28000 dpi, dmax of 4, Wax Dmax of 4, DTS ink jet Dmax varies, solids can hit 4 tonals do not, Ink Jet 3.5, low tonal percentages of <10% can be at dmax of 2-3.  The lower the dmax, the more transparent the image, the lower the exposure time, the lower the cross linking quality of the sensitizer, the weaker the screen.

Short fast exposures create an image but do they cross link the emulsion completely?  I am beating a dead horse, but seriously do you under inflate your car tires because it's faster than waiting until it hits 32psi?  Or pull the frozen pizza out of the oven cause it's faster then waiting?  It's not how fast you expose a screen, it's how well you expose a screen that matters.

Cross linking equals durability and print quality.  If you have to underexpose to get details maybe the film image needs more density to withstand a longer exposure, or maybe a yellow mesh on the base plate would allow longer exposures and avoid halation.  Having issues reclaiming that SBQ emulsion?  Often due to un-cross linked sensitizer that gets chemically flashed with screen opener, acetone, or even mineral spirits.

So with LED DTS exposure calculators don't work.  LED has a hard time getting through 2 layers of film for accurate results with a calculator.  Getting accurate times requires accurate consistent EOM and coating techniques.  Analyzing each mesh count during development for slime on the inside of the screen, or emulsion color coming off on a white piece of fabric, using loupes to look at halftones and fine details, pushing exposure up to the maximum just before over exposure is key in getting the most out of your LED unit.

[3Deep]

So with LED DTS exposure calculators don't work.  LED has a hard time getting through 2 layers of film for accurate results with a calculator.  Getting accurate times requires accurate consistent EOM and coating techniques.  Analyzing each mesh count during development for slime on the inside of the screen, or emulsion color coming off on a white piece of fabric, using loupes to look at halftones and fine details, pushing exposure up to the maximum just before over exposure is key in getting the most out of your LED unit.

Right here is where I'm at with this new LED point light, use to get a nice screen with my old unit at 3 minutes + (1000 watt halogen with two 30 watt fluorescent bulbs) which I can no longer can get the fluorescent bulbs.  My problem was using the same emulsion HXT which was burning fine but leaving a slime on the squeegee side and getting lots of scumbing after washout, which I know is undried emulsion running back into the image area.  What made me ask the question of color is I changed to VPR which is pink and I got a full burn at 11 seconds and the HXT is blue, but I did read the specs and the VPR is a fast exposing emulsion, so VPR will be my main emulsion and I will buy qt's of other stuff to test, so I can have a second emulsion to buy.  Thanks all and Allan for the post, Oh yeah I still have glass on my unit and use film so I know the glass will block some UV even though it's clear glass.

[Dottonedan]

As usual and expected, a great post by Abuffington.  The only comment I could have is a testify to my own experience on the Dmax of inkjet.
 
I’ve tested this specifically on the I-Image STEll with a densitometer that showed 4.8 Dmax at a standard install setting of a 12 pass hi speed bi directional setting. True that you can have varied values but not that extreme near the 2’s  it would just burn up (dot loss below 20%) in the 2’s of Dmax . If I had to guess, nobody could ever produce a 45,  55lpi -65 LPI full gradation ever and we know that to not be correct.

I did this under the watchful eye of another pro separator who was the owner of a shop that is well known for high end film positive service provider. I say that to show this customer went to great lengths to be sure of what he was buying.  Results were very good.

[screenprintguy]

HXT is a super slow exposing hybrid emulsion. From what I know, the color has nothing to do with it. On my starlight, if I use HXT, I'd be at 40 seconds for a murakami 150s mesh. With Murakami T9 I'm at 7 seconds. It's just a faster exposing hybrid emulsion. If you went to Chromatec WR, you'd even be a bit faster. Both the WR and the T9 are fantastic for plastisol, or waterbased and discharge with a post exposure. We prefer the T9. Never let's us down, super fast exposures, and the proof is in the detail. HXT was our go to several  years back, but once we found the T9, that was it. It may be a little more expensive, but like the old saying goes, you get what you pay for. Hope ya'll are doing well big D!!

Mike