Wow, Exposure Latitude w/ HVP

[alan802]

I just accidentally burned a 205N for about 12-15 minutes instead of the 45 seconds that we normally do.  Our blanket needs replacing so we're bypassing the automatic on/off function on the Richmond and I walked away from the expo unit and was getting things ready to coat a batch of screens and when I came out of the darkroom I had been in there at least 12 minutes because I was cleaning scoop coaters and pouring down the 5 gal pail of HVP into gallon buckets among a few other little things.  I put the screen in the post expo dip tank and then let it sit for 20 minutes or so while I coated screens.  Took it out and started washing it out and although there were signs of undercutting in the beginning the entire screen with 1/2 point lines and text for the standard back print of sponsors logos that we all know so well sprayed out and is completely usable.  I've known for a while about the lengthy exposure latitudes that we've experienced when developing discharge ready stencils but this one went far beyond that.  One of the knocks on the pure photopolymer emulsions is the lower exposure latitude versus the dual cures, but how can anyone be disappointed with this type of latitude with a PP emulsion?  I know this is with a metal halide bulb but I'd think the new LED's should have similar latitudes since all of the screens I've tested with LED against our MH bulb has given almost identical results and times with a new MH bulb.

What do you guys consider a great exposure latitude?  I would think with a PP that 30 seconds on a 156 would be great but the 12 minutes or so I just did blows that out of the water by a mile.  Food for thought for all you shops that don't like to use PP emulsions because of expo latitude.

[ABuffington]

Thanks for the feedback.  It's posts like this that make my day. One thing about Murakami emulsions is they are designed for complete exposure and as shown above you can over expose and still wash out details.  This would be the toughest screen for discharge you could create.  The time is a little long, but the point is expose it as much as you can before seeing loss of details and quite often hardeners won't be necessary.  We develop here with a 2000psi pressure washer, and on fan spray I can work fine details with no loss of exposed emulsion halftones, even with the washer at 4", just keep it moving to get those sub 5% tonals to develop. (Degrease it well!)   Thanks for the post, I can now go play music.

Al

[3Deep]

Good post Alan but you know we are in the world of needed it yesterday but I'm telling you about it today so you can print it for me this afternoon, are you that fast.  One of these days some one is going to figure out how to run the cart ahead of the horse.  I hate to be the ole meanie around here all the time (the ole sour pus) but if we keep up with a our fast pace give it to now right now! we're going to work ourselves right out of jobs.

Darryl

[ABuffington]

I had a client who told his rush customers if they had paid him yesterday it would be done already!  Kind of puts it in perspective for the customer who doesn't plan.  Another spin I have seen is the old 'An emergency on your part does not constitute an emergency on our part, unless your willing to pay double!"

[alan802]

I was thinking the other day about this thread and the few LED shops that have mentioned moving to a dual cure emulsion because the pure photopolymers are exposing so quickly and I'd like to know why someone would do that.  One of the advantages of LED is speed and if you can develop a stencil in 10 seconds then that's awesome and moving to a dual cure will erase a huge portion of time savings and you'd be going back to taking about the same amount of time to expose a PP emulsion on a strong metal halide unit.

I also haven't played around with other PP emulsions with regard to exposure latitude but this HVP is unbelievable.  I exposed a 150/48 for 2 light units the other day then a 180/48 for 20 LU's for a difference of 18 LU's and they both sprayed out with ease.  I also did a 305 for 1 LU and it developed just fine with no slime on the squeegee side and it held up for a 150 piece plastisol run.

Does anyone have another PP emulsion they'd mind doing some testing on?  It would be easy to let a screen expose for a bit longer than usual and share the results.  Hopefully you won't ruin any screens if the latitude is somewhat decent.

[dirkdiggler]

Kiwo Discharge tests in the M&R booth in Nashville on the LED was 2 seconds on a 250 mesh.

[GraphicDisorder]

Kiwo Discharge tests in the M&R booth in Nashville on the LED was 2 seconds on a 250 mesh.

I dunno the brand but watched M&R do as PP at 3-4 seconds on a LED Starlight.

For us at 3-4 second burn wouldn't speed us up in our CURRENT configuration. Takes about 30 seconds or so to wash out a screen, so burning faster than that wouldn't be much help.  Right now we can burn and wash (2 people) in a constant flow on Diazo. 

[dirkdiggler]

Kiwo Discharge tests in the M&R booth in Nashville on the LED was 2 seconds on a 250 mesh.

I dunno the brand but watched M&R do as PP at 3-4 seconds on a LED Starlight.

For us at 3-4 second burn wouldn't speed us up in our CURRENT configuration. Takes about 30 seconds or so to wash out a screen, so burning faster than that wouldn't be much help.  Right now we can burn and wash (2 people) in a constant flow on Diazo.

Exactly, as soon as my starlight shows up, we will not be using PP anymore.  My unit will not have glass, so it will probably be even faster.

[blue moon]

I was thinking the other day about this thread and the few LED shops that have mentioned moving to a dual cure emulsion because the pure photopolymers are exposing so quickly and I'd like to know why someone would do that.  One of the advantages of LED is speed and if you can develop a stencil in 10 seconds then that's awesome and moving to a dual cure will erase a huge portion of time savings and you'd be going back to taking about the same amount of time to expose a PP emulsion on a strong metal halide unit.

I also haven't played around with other PP emulsions with regard to exposure latitude but this HVP is unbelievable.  I exposed a 150/48 for 2 light units the other day then a 180/48 for 20 LU's for a difference of 18 LU's and they both sprayed out with ease.  I also did a 305 for 1 LU and it developed just fine with no slime on the squeegee side and it held up for a 150 piece plastisol run.

Does anyone have another PP emulsion they'd mind doing some testing on?  It would be easy to let a screen expose for a bit longer than usual and share the results.  Hopefully you won't ruin any screens if the latitude is somewhat decent.

going to dual cure provides a better waterbase/discharge strength and the emulsion is cheaper. Not having to monkey around with hardeners and saving money if it is not impeding the work flow sounds like a good idea!

pierre

[3Deep]

I've been in love with dual cure for the last 3 to 4 years now, I still have my PP which I use but found out dual cure really holds fine lines and halftones very well for the exposure unit I had at the time combine with using it on yellow mesh.

Darryl

[JBLUE]

HVP and Photocure Pro are the only two emulsions you really need. I have tried all the others. I always end up back with these.

[dirkdiggler]

HVP and Photocure Pro are the only two emulsions you really need. I have tried all the others. I always end up back with these.

I always wanted to try HVP, I here good things and HVP is name of my company, imagine that.  WR14 will probably be my go to once the LED gets here.

[TCT]

HVP and Photocure Pro are the only two emulsions you really need. I have tried all the others. I always end up back with these.

I kept coming back to the HVP also. Tried other samples of other things and it was probably a mixture of not dialing the exposure times in 100% on the sample emulsions and rushing to conclusions. The HVP was just always what I have known. It has been probably a month or better now and we have fully switched over to the SP1400. Aside from the added exposure times I am really liking it! Performs great with WB/DC with no post exposure or MS hardener.

[mk162]

I tried HVP, it's good, I like it.  i might try it again.

My favorite all time emulsion is Image Technologies ITX, the problem with it is it's too fast for our exposure unit.

Xenon's Nova with diazo is awesome, it's just too tacky.  Might check this out too with the CTS...no more film getting stuck to it.

[abchung]

We use Macdermid Autotype.

If the emulsion is still tacky, it is an indication for us to dry the screen longer.