Discharge and Our Vastex LED

[alan802]

Since buying the Vastex LED we haven't had much need to do any discharge work so I was excited this past week to see 3 new discharge jobs come in but I was apprehensive at the same time with our poor results with most every aspect of our LED unit.  I had this really detailed review of what we've seen, the whole routine we used to make the screens, the emulsions tried, etc, but I just deleted it all and I can sum it all up in one word:  SUCK.  It's my own fault, how in the hell could I have thought that I'd get anything other than poor results?  I still can't believe I thought it would be fine.  So not only can we not produce a good sim process screen above 50lpi, we can't seriously do any waterbased or discharge printing until I jump through so many hoops, do a lot of back flips, hold my finger in the air just right while wearing a tin foil hat, AND PRAY the screen holds up.  I don't like those options.  This shop has steadily progressed over the years into something we're all proud of, and to think that we've had to take a step backwards in our quest to be one of the best doesn't sit right with me.  I know some will think I'm an insane person, that what I'm asking of a piece of equipment isn't reasonable, I need to get over myself and deal with it's capabilities like everyone else because we're not special...I don't see it that way.  Anything less than our best isn't good enough, and over the last year I've tried so hard to keep moving this shop in the right direction and I've finally hit a plateau (actually we've digressed) due to something that did not come with any fine print or disclosures like what we've had to deal with.  It's very bothersome to me.  How could I be the 1st person (that I know of) to have something negative to say publicly about an LED exposure unit?  Were we the first to actually put an exposure calculator on one?  Were we the 1st to fun a few hundred impressions on a screen and have the stencil fail?  Surely not.  Now were we the 1st of active forum members to do those things I asked?   Again, I seriously doubt it.

I can say that if you're seriously looking into this particular LED for your next exposure unit, you still could love the product depending on what you ask it to do.  If you want to do high-end sim process work, it's not for you.  If you want to do virtually any WB or DC work on an auto...probably not for you.  If you use thicker stencils, not for you.  Low mesh counts (thicker stencils)...again, not for you.     

What is it good at?  Doesn't use much energy, the bulbs don't weaken much over time, it doesn't put out much heat, it will do the basic, run of the mill spot color stuff all day long without much problem until you get the screens on press for longer runs, then it really isn't very good at all.

I went further with these DC screens than I thought would be necessary so I wouldn't have to worry much about the screens breaking down on press.  I used a very good water resistant emulsion, a dual cure, tripled the recommended exposure time, blockout, hardener, 10 minute post exposure on the expo unit, sat it out in the sun for an hour, then let them sit for 24 hours before we used them.  The only thing I haven't done with regards to DC screens is test a ton of different emulsions.  I feel confident though since our results were on par with what we're seeing with our plastisol screens and at least 15 different emulsions, I think I'd be wasting my time testing out a bunch of DC emulsions.  And everyone that knows me knows that I didn't just put some emulsion on a screen and shoot them and call it "tested", and to do all of that again for DC ink isn't going to happen any time soon.

Am I out of line to expect this expo unit to be able to consistently produce single digit % halftones of even 50lpi?  What would everyone here expect to be able to get on a standard exposure calculator as far as halftones go?  10% at 65lpi?  5% at 50lpi?  Or am I shooting too high? 

So with ALL of that being said, who wants to buy a used Vastex LED unit?

[GraphicDisorder]

Time to move on to something else, you've spent almost what it cost in monkeying with it I would suspect.

[ZooCity]

Yep its time to get that thing out of there the Richmond solarbeam you have is an excellent exposure unit. Fix it up and get back to work, and sanity.

Sent from my SM-G900V using Tapatalk

[Ross_S]

I don't know much about the vastex unit but I love my star light and would never go back to a halide unit

[GraphicDisorder]

Have you tired a Star Light Alan?  Isn't M&R sending a guy around with one to try out?

[3Deep]

Alan the Starlight that Ron Hopkins brought to our shop did very good job on exposure even on some old high detail film I got from Scott Fresner many years ago, so I'll have to say the starlight would be a good option even thought we don't have one and happy with my old unit right now.

[blue moon]

if you had the screens in the sun for an hour and are still having problems, it is not the exposure unit! Anything not crosslinked by the LED unit would be finished by the sun. If the sunlight is not completely crosslinking your screens, the issue should be somewhere else.

For comparison, we are now using an entry level SAATI LED unit at 50 second exposure time. Aquasol HV is giving us about 100-200 discharge prints straight out of bucket. If we put it out in the sun, we are getting 500+, even up to 1,000. We are also testing the SAATI PHU and are getting about twice as much on the discharge runs. All of these are without hardener.

pierre

[UnderPressureSP]

I still think 6k lamp or higher is the way to go with large vacuum table.  So you can burn 2 screens a time and get the proper cross link.  We recently up dated our film systems and that helped a lot in being able to hold half tones that were 50lpi or higher.  I wondering if your old unit could be repaired.  Did you have a tech ever look at it?   Or call Richmond to trouble shoot the problem.  The last time our nuarc went down a hour later with M&R we had parts ordered and fixed it the next day. 

[3Deep]

I agree with P we don't have the best exposure unit in the world so when we do expose for discharge I sit our screens out back after washout in the sun to dry and they are rock solid using HXT emulsion.

[Frog]

I agree that even ten minutes in the sun should fully crosslink any photopolymer or dual cure emulsion.
That old sun is one giant mutha' of a single point UV light source!

[Colin]

As I understand it:

Dual Cures get little to no benefit from sitting in the sun/post exposure.  Something about how the molecules position themselves.  I think it was a Saati article?  Or maybe Al posted some of his great wisdom about it....

It's the emulsions like Murakami's Aquasol and Saati's PHU that do benefit from post exposure.  The SBQ's if I remember right.  Someone please correct me if I am wrong.

If the bulbs are not emitting light in the correct frequencies for a dual cure, then the screen is doomed from the beginning.

Even using a chemical hardener will not give you the life expectancy (and detail) you desire.

Sorry to say Alan, yep you need a better light source.

[jvanick]

I'm not 100% convinced that the starlight puts out the optimum light for these emulsions either.

Diazo is 360nm
SBQ is 405nm

Starlight is 385nm

[Frog]

As I understand it:

Dual Cures get little to no benefit from sitting in the sun/post exposure.  Something about how the molecules position themselves.  I think it was a Saati article?  Or maybe Al posted some of his great wisdom about it....

It's the emulsions like Murakami's Aquasol and Saati's PHU that do benefit from post exposure.  The SBQ's if I remember right.  Someone please correct me if I am wrong.

If the bulbs are not emitting light in the correct frequencies for a dual cure, then the screen is doomed from the beginning.

Even using a chemical hardener will not give you the life expectancy (and detail) you desire.

Sorry to say Alan, yep you need a better light source.

I thought that as well, but was corrected that the diazo does not negate the positive effect that the photopolymer receives.

[Orion]

I believe you are correct, Colin, about the post exposure benefits being only for pure photopolymers.

Another, very important, consideration is pre-exposure moisture content of emulsion coating.

As jvanick pointed out he, I and others perhaps, are not totally convinced that LED can fully expose emulsions because of the lack of broad spectrum emission.

Alan if you have not yet tried the Kiwo multitex SBQ get Bill Warren to get you a sample. We switched to it from SP1400 and are very happy with it.

[screenprintguy]

Digitsmith that turd and get that starlight bro. Guys using it and a good emulsion are rockin some serious discharge prints trouble free. We are getting one here soon as soon as I have a buyer for my tri light. The Trilight exposes awesome trouble free discharge screens no problem, I just want to free up a bit of room in my imaging room using the star light. If you had CTS, you could always just walk those imaged screens out in the sun. I've done it when waiting on a new bulb to come in. I taped a peice of cardboard to the inside of the screen, set it on the roof of the car, went in to take a piss, came out rinsed it out, and that puppy was exposed like steel. full detail because of the cts. Great back up plan!!!