[reactiongfx]

This job is going to be the death of me! Did a run of 3-color shirts and hoodies a few months back and had lots of issues with the top colors washing off the underbase after only one wash. Pretty certain I was over-flashing the underbase. Doing another run now and want to be sure I don't have this issue again. Here's the process I'm using this time:

1) print first hit of white underbase (One-Stroke FF Hybrid White)
2)flash 8 seconds
3)print second hit of white underbase for bright white since these are all going on dark garments
4)flash another 8 seconds
5)this time around I'm hitting it with a flattening screen to try to reduce the rough texture I got on A LOT of the hoodies last time. Just a coated, exposed screen with no image, one firm hit.
6)print red (Union Ultrasoft Bright Red)
7)print blue (Union Ultrasoft Royal)
8)cure in conveyor dryer to 325-345 for 5-10 seconds

I did a bunch of test print this time and they all passed the stretch test so I went to the wash test. They all still looked good out of the washer (front loader), but after putting them through the dryer at medium heat, 3 of the 4 tests have some minor spots of red/blue ink washing off. The only one that came out acceptable was 8 seconds of flash for both white hits at about 2-3" above shirt, but it was a really fine line between being gelled and still leaving ink on my finger. The shirt I did at 10 seconds per flash had minor washing out. It's also impossible to get an accurate temp reading with my laser when flashing because I think the warm platen is affecting my readings.

Anyone have any tips/tricks here? I have like 90 shirts, some front and back (all prints are a similar 3-color design), and 110 hoodies to print and I'm definitely not feeling very confident. This could be a very costly mistake if I screw up a second round of prints.

 

[Ripcord]

5-10 seconds in the dryer isn't long enough. It should be at least a minute to make sure the entire layer of ink reaches the cur temperature. Also, make sure the whole print surface reaches your target temp, not just the center. Take a reading with a laser thermometer and you'll find the edges are significantly cooler than the center.

 

[reactiongfx]

5-10 seconds in the dryer isn't long enough. It should be at least a minute to make sure the entire layer of ink reaches the cur temperature. Also, make sure the whole print surface reaches your target temp, not just the center. Take a reading with a laser thermometer and you'll find the edges are significantly cooler than the center.

This seems to be a hotly debated subject. Some folks say it only needs to REACH 320 degrees and DING! it's cured, other say it needs to dwell at 320 degrees for anywhere from 10 seconds to a minute. (First I've ever heard anyone say a minute for plastisol, though.) My shirts are in the chamber for probably 30 seconds, but only up to temp for 5-10. I do understand it needs to be 320-ish all the way through and I'm definitely laying down a thicker deposit of ink, but my current dryer is just a Ranar Scamp, so lengthy dwell time is difficult to achieve. I'd have to run them through so slow production will take absolutely forever, and I'm sure things will probably get scorched.

Here's the thing, though, the white ink seems totally fine. It's only the top colors washing off the white. The white is not washing off at all and didn't wash off any of the previous run. Wouldn't the top colors cure before the underbase? This would lead me to believe it has to do with the flashing--I'm overflashing so the top colors are just not adhering to the white base. I could be wrong...but I'm certain I was overflashing on the last run.

If you honestly think this is due to undercuring, I can experiment with dryer settings and try to get more dwell time, but there is absolutely no way I'm going to get a full minute.

Believe me, a bigger dryer is #1 on my list of equipment to buy. My dad has used this Ranar Scamp for probably 25 years and it suits him fine, but he does mostly single-color, simple stuff using 110 screens for pretty much everything (old school). He also only prints a few small jobs a month. My clientele is vastly different and this is my business, so my production is much higher and my customers expect more from me. This dryer just ain't cutting it.

 

[gardenhillemb]

If you aren't sure the shirts are curing completely, heat press them and then wash test. If they come out ok after heat pressing, then you're not curing enough. Also, use your laser temp to check the flash and see if you're curing the white ink during flashing.

 

[reactiongfx]

If you aren't sure the shirts are curing completely, heat press them and then wash test. If they come out ok after heat pressing, then you're not curing enough. Also, use your laser temp to check the flash and see if you're curing the white ink during flashing.

I am using my laser temp gun during flashing, but I think it's picking up the heat of the platen or the white is reflecting heat because almost immediately after putting it under the flash I'm already getting a reading around 190. Trying to keep my flash temp below 215, but it seems very difficult to get a good reading.

I did try heat pressing some prints during the previous run to attempt to smooth them out (the hoodie prints in particular were REALLY rough, and I know that's another issue entirely), and if my smoothing screen doesn't help with that this time around, I may try the heat press again. It worked pretty well on some thermal longsleeves, but when I tried it on a few hoodies it seemed like it was pulling off some of the red and/or blue ink. I was doing it at 350 (I think), using just the weight of the press (didn't even clamp it shut) for like 2 seconds. I was using some parchment paper over the prints. Didn't try a Teflon sheet, but maybe I will this time.

 

[Industryps]

It sounds like you are over-curing the underbase and under-curing the additional ink layers.

You may want to try hitting the red and blue after the first hit of white, flash, and then hit the white again with a highlight screen instead of another underbase. This will give you smoother printing surface, and should save you time in your printing.

However you go about your printing, you let the shirts cure a little longer in the conveyor dryer making sure the shirt is as flat as possible because air needs to circulate around it.

 

[reactiongfx]

It sounds like you are over-curing the underbase and under-curing the additional ink layers.

You may want to try hitting the red and blue after the first hit of white, flash, and then hit the white again with a highlight screen instead of another underbase. This will give you smoother printing surface, and should save you time in your printing.

However you go about your printing, you let the shirts cure a little longer in the conveyor dryer making sure the shirt is as flat as possible because air needs to circulate around it.

I think you're absolutely correct--overcuring my underbase and undercuring my top colors. After printing about two dozen scrap test shirts, last night I was FINALLY able to get good results. I flashed for 8 seconds per hit of white, then tweaked my dryer settings to slow things down enough so that the shirts are hitting at least 310 for a good 25 seconds or so. My last four test prints all looked good and they all passed the wash test! YAY! Now I just need to do that consistently for about another 375 prints!

I've tried using a highlight white screen in the past as I've read that is really the proper way to do it, but I felt the red and blue were nowhere near as vibrant as they are when printed on a bright white underbase. Plus, I only have a 4-color press right now and I think the blank flattening screen I'm using on the underbase this time is making a world of difference in the overall feel of my prints.

Thanks for the input, everyone!

 

[Industryps]

Congrats on getting it to work!
A flattening screen is a great idea, definitely sounds like you have a good grasp on what you're doing.