[BLTNJ]

Hi, i'd really love any feedback on this issue. I'm still fairly "new" to screen printing. I'm in the middle of a 3 color job and i'm using yellow 230 mesh. This mesh i'm sure is a bit overkill for the design but it happens to be the screens i have the most of atm. The emulsion is breaking down just a bit around 20 shirts in. This happened on a previous job so I added about 30 sec to the burn time. I have an 8 bulb black light exposure unit. I'm using a hybrid emulsion and i'm doing 1/1 with the rounded edge of the coater. I'm wondering if I should do 2/2 or maybe burn them even longer. I did do a burn test on these very screens and our best results were around 4 min 15 sec. I've since upped it to about 4 min 45 sec. No slime/residue during washout. I feel I degrease them well too. I'm really stumped here and it's frustrating because i'll have to re burn one of the screens to finish this job. Also this particular job is water base ink and I use a push stroke. Once again any feedback would be awesome. Thanks in advance!

 

[20vK]

Water based ink is almost certainly breaking down your emulsion.

Swap emulsion or buy and rub in a hardner.

Check out the info for your particular emulsion to see if it's suitable for WB ink. What emulsion is it, exactly? Brand and type?

 

[BLTNJ]

Hey Rich, thanks for the reply! The emulsion i'm currently using is from Ryonet... it's WBP Hybrid Emulsion: Diazo Sensitized Photoemulsion... says recommended for plastisol and water base inks. Also says it has "excellent water resistance"... I have heard of the hardeners you can add... (didn't think of that). I've also heard of people clearing out the stencil and then burning again briefly to harden a bit... is that a common practice? Thanks again.

 

[Fresh Prints]

Hey Rich, thanks for the reply! The emulsion i'm currently using is from Ryonet... it's WBP Hybrid Emulsion: Diazo Sensitized Photoemulsion... says recommended for plastisol and water base inks. Also says it has "excellent water resistance"... I have heard of the hardeners you can add... (didn't think of that). I've also heard of people clearing out the stencil and then burning again briefly to harden a bit... is that a common practice? Thanks again.

I was having this same problem with wbp, I eventually switched emulsions with hardener and did OK. But I just recently got a new gallon of wbp. I have the same 8 bulb exposure, I burn for 6 minutes, washout, dab dry with news paper and expose again for 5 minutes. I have always post cured my screens. Either in the sun or ink side towards bulbs after drying. I am now getting perfect stencils, no hardener needed. I just did 55, 2 color discharge, along with 15 plastisol and it worked great.

On a side note. When I was using hardener, I did lock in a couple 230s with it. Oops... So if you do use it, I find using it in small amounts on ink side only helped to not lock the emulsion.
Also If anyone knows how to unlock those it would be appreciated.

 

[BLTNJ]

Wow... I think i'm gonna try that. I was going off "recommended" burn times. If you're telling me you've had success with a FULL 6 min burn and then an additional cure ink side down, i'm definitely gonna try that. I suppose the reclaiming may take a bit more elbow grease... but i'll trade that for screens breaking down in the middle of a run anyday! Thanks for the reply!

 

[daynawalraven]

i had this problem too. the help desk at ryonet told me to post harden the screen either in the sun or the exposure unit. i let the screens sit in the sun for 5-10 minutes and the problem was gone! ryonet said that sometimes all the emulsion is not exposed or dryed properly, so the post hardening fully exposes everything eliminating the stencil break down. i also tried out the new emulsion from saati, phu. it's a photo polymer emulsion for waterbase, discharge and plastisol. it exposes super fast and i haven't had any break down issues. it also has a one year shelf life.

 

[Fresh Prints]

Yes I have had success with these times, I tried "recommended time" but It didn't work for me, but there are alot of variables that could affect it.
My bulbs may be older or the emulsion coating etc... I use the pressure washer for washout.
Reclaim is not bad, it breaks down pretty easy with Envirostrip and a pressure washer.

I usually burn the SVP photopolymer for 3.5 to 4 min. and its held up fine for plastisol and solvent ink.
I hope you get it all dialed in, Good luck.

 

[20vK]

How is your humidity? If it's above 40% then your emulsion may not form cross links during the exposure process, leaving you with a weak emulsion.

 

[BLTNJ]

First of all... these forums are great lol. Even more confirmation from all you guys on the "post hardening". Setting them out in the sun is also a great idea because I can continue to burn other screens while the burned ones are out in the sun. As far as humidity... I think i'm okay. It does get a little humid/warm in my darkroom but I don't think it's anywhere near 40% (at least right now). I will definitely do a check on that when it starts getting really hot outside. Good stuff guys! Really appreciate the feedback!

 

[jgabby]

Here is a usefull link about climate control.
Climate Control | Printwear


Screen + humidity can be a real pain.

A simple harderner that can be use is white vinegar.
I like Ulano Hardener X

 

[tpitman]

When I was in a commercial location, I always set my screens out in the bed of my pickup after shooting and washout to let the sun have a go at them. I still do it when I've got a bit of sun, or at my part-time job in Daytona if I need to reshoot a screen and have to get it right on press.
They'll dry in about 5 minutes, if that long, and they're as "post-exposed" as they're ever going to get.