Before You Went LED, What Were You Using?

[Orion]

Other than under exposure or bad emulsion, take a look at stencil moisture content. If the moisture level in the stencil is not at an acceptable level before exposure it does not matter how long you expose, you will never get good results.

edit: that should read "below an acceptable level"

[KevWilso]

We're on a starlight...

This is 3 different batches of emulsion... however, I guess it's possible that our supplier screwed up and let it freeze in their warehouse over the winter...

I have a gallon of Ulano Proclaim EC coming in today that I'm going to give a shot...

If you send me you UPS OR FEDEX shipper number I will send you out a sample of the 1400 no charge.  At least then you have an new batch from a new supplier with a different lot number.  This will remove a lot of variables.

[alan802]

Today I decided to crank up the burn times and I did the white shirt wipe test on the squeegee side of the screen on a 150/48 with 20% EOMR, FAIL.  Damn, I really thought 90 seconds would more than cook a 150.  Needless to say the 120/54 with similar EOMR but a bit thicker stencil overall didn't pass the test either.  There were days in the beginning that we were shooting a 150 for 15 seconds and getting a usable screen for plastisol, although it would break down at the squeegee edges.  I'm going to keep going up in burn times and keep everyone updated.  Oh yeah, pure photopolymer emulsion, orange color, good emulsion, but not as good as HVP.  It's River City's house brand and I don't know if anyone here is using it but for the price it's hard to beat.  I think I'm going to get a gallon of the HVP and work it in with the current screens to see if I can find something.

[Gilligan]

I wish every manufacture was willing to send you a demo unit to put through the test Alan.

A true independent shoot out would be great!

[Orion]

@ Alan, humidity has been really bad here in CenTex for the past few days. Moisture content in your stencil, pre-exposure, is worth looking at.

I measured 78% percent today in our production area and we were  having a bit of a tackiness issue this morning running discharge on 225S coated 1/1 with SP1400. Applied hardener to the next DC ubase screen and that seems to have helped.

[ebscreen]

Orion are you using an LED exposure unit?

[Orion]

No eb, and I don't foresee bringing one in here any time in the near future.

[alan802]

@ Alan, humidity has been really bad here in CenTex for the past few days. Moisture content in your stencil, pre-exposure, is worth looking at.

I measured 78% percent today in our production area and we were  having a bit of a tackiness issue this morning running discharge on 225S coated 1/1 with SP1400. Applied hardener to the next DC ubase screen and that seems to have helped.

I've been watching it closely, it's been tough keeping it below 45% in the screen room but we've managed to keep it around 40 most of the last week.  The screens have been tackier after washout but I think we're able to get them developed quick enough to keep the moisture from affecting exposure, but I know the screens are drawing in moisture pretty quickly. 

Anyone have any idea how fast a dry, coated screen can go from dry to moist in a humid environment?

[ZooCity]

Anyone have any idea how fast a dry, coated screen can go from dry to moist in a humid environment?

I wish I did.  Purchased a humidity sensor, the type used for lumber typically, and had one of my crew file the pointy tips down and polish but it won't read on a screen, not enough surface area I guess.

[Gilligan]

Anyone have any idea how fast a dry, coated screen can go from dry to moist in a humid environment?

I wish I did.  Purchased a humidity sensor, the type used for lumber typically, and had one of my crew file the pointy tips down and polish but it won't read on a screen, not enough surface area I guess.

Well, that saved me from doing that myself.

[jvanick]

after a whole lot of testing with Al from Murakami ... I don't think we have a bad batch of emulsion, at least now...

I think that there's a combination of issues going on:

1. we had EOM of around 30%, which he feels is too high... started coating 1/1 sharp on our 160S mesh and the EOM is now down around 10%, too low for me to be super comfortable with, but we'll work that out...

2. exposure times are definitely longer than the SP1400-W, why, I have no idea, but we're now settling in around a minute or so.

3. our first and second batches of emulsion had expired/bad diazo, which started this whole debacle...

We are playing with Ulano Proclaim EC as well now too... shot a few really good screens with it, at roughly the same as the SP1400... (about a minute on a 160S)... I am digging the fact that it's a dual cure that you don't have to sensitize, and it has a shelf life of 18 months...  with that being the case, I might get some Pure Photopolymer that's better suited to the Starlight and have 2 emulsions... 1 for waterbase/discharge jobs, 1 for pure plastisol... still haven't made up our mind on this yet.

Kev from River City is sending me a sample of SP1400 from his warehouse too, so we'll be testing that as soon as it gets here.

[alan802]

Yeah, 30% would cause some problems for us.  The MH unit didn't really struggle with thicker stencils but the Vastex definitely does.  For low mesh I still like to be around 20-25%, middle mesh counts 15-20% and high mesh counts are 10-15%.

[T Shirt Farmer]

My shop-HVP 2 over 1 on everything every time - vastek LED set 30/ 110-135 mesh  25/ 150 -180 mesh  20/225  15/ 280 and up-  works every time we have no issues at all - my shop

[alan802]

My shop-HVP 2 over 1 on everything every time - vastek LED set 30/ 110-135 mesh  25/ 150 -180 mesh  20/225  15/ 280 and up-  works every time we have no issues at all - my shop

Wow, our screens won't reclaim at those numbers anymore.  That looks really close to the numbers I got when using the expo calculator and we used similar numbers for months.  We coat most S thread with a 1/1, glisten method, but a really slow coating speed so I usually get a glisten with one stroke.  I don't have to use the 2/1 until I get to the 280's.

[jvanick]

so far, really liking the Proclaim EC... shot a bunch of screens this morning with it... it's almost like a pure photopolymer in that the open areas literally just fall out of the screen after a minute or 2 in our post-exposure soak tank. (new kitson terminology)