Strange Curing Problem - White Ink

[GraemeDeroux]

Yo, what's going on?

Having a bit of an issue these days - can't sort it out. Done the best I can to try to solve the problem myself and having no such luck.

I am having an issue with undercuring on dark garments. Specifically Alstyle 1701 and G500's.

First I had a 2 colour job come back as a washout. Tan and white, flash, white highlight on a black alstyle 1701. Assuming my problem was time spent at 320 and not actually getting to 320, I slowed my belt right down, and raised my element. Giving off a solid 340 - 350 for around 5 seconds. Long enough - or so I thought.
I re-printed the job, haven't had an issue yet with that.

Second, I had learned my lesson and began wash testing before sending out garments. Leaving an extra day and ordering one extra that I would take from the middle of the run. I was doing temp tests at the beginning and end of the dryer belt. First item, mid-run, and then final item. I am SURE that this item was pushed to 340 - 350 for long enough. Some were even hitting 360. Not torching garments, but absolutely getting hot enough and all the way through.
I printed a charcoal G500, one pass of white. Through the dryer, reaaaal slow. A small nape print, the size of about a business card. Getting up there at 360 - 380 for around the same, 4 or 5 seconds, checked beginning, middle, and end of run again. Test washed that, and boom. Print could basically rub right off. After wash one, I was missing half a print. The stranger thing is that the front of the shirt, cured at the same belt speed / temp didn't even move and it was an entire chest print. Cured PERFECT.

Anyone have any idea what is causing this? I know my dryer is maintaining heat - I know my temp gun works. I know both sides of my dryer element is working. Am I getting too hot now? Not long enough? What do you guys suggest?

I printed through a 110 screen, cured in a 110v conveyor dryer, vented at the very end and not through the oven, so not interrupting the chamber. Printing with Wiflex Super Bright White.

Suggestions? Advice? I am happy to try anything. I'd really love to stop having to run my garments through a wash test on every single job in order to make sure they won't come back freaked. My dryer is working because I tried to torch a garment this morning and with the belt slow enough will do it on ANY spot on my belt.

[mimosatexas]

110v dryer with a single element? I'm guessing the heat chamber is like 20" long, right? No baffles, skinny belt so shirts are being folded to fit through, etc. We use one of these at live events and set it so exit temp is 400ish with a laser reading. Its not even under the element long enough to scorch in our experience. Dwell time in the whole chamber is like 15 seconds max, which makes controlling the actual cure temp through the whole print basically impossible. One thing on our dryer we noticed and part of why we have it cranked so high is any air movement will cause drastic swings in the surface temp of the garment. Fans, ac kicking on, gusts of wind if you're printing with a door open, event just the act of laying the next shirt down on the belt can cool off the shirt massively in the chamber.

[Doug B]

  What Mimosa said... 4-5 seconds at cure temp? That should do for a flash
but not a full cure. The backs held up better than the L/C because even though
the print was down, it still went through the dryer twice and the L/C only once. If
you can't slow the belt any more then at least run them through twice and start saving
up for a better dryer.

[GraemeDeroux]

110v dryer with a single element? I'm guessing the heat chamber is like 20" long, right? No baffles, skinny belt so shirts are being folded to fit through, etc. We use one of these at live events and set it so exit temp is 400ish with a laser reading. Its not even under the element long enough to scorch in our experience. Dwell time in the whole chamber is like 15 seconds max, which makes controlling the actual cure temp through the whole print basically impossible. One thing on our dryer we noticed and part of why we have it cranked so high is any air movement will cause drastic swings in the surface temp of the garment. Fans, ac kicking on, gusts of wind if you're printing with a door open, event just the act of laying the next shirt down on the belt can cool off the shirt massively in the chamber.

Wow very helpful. I originally had this dryer set to have an exit temp of around 400 and I was nervous I was actually torching garments. So I turned it down.

I am going to raise up the element, and slow down the dryer even more and do some tests. Thank you for this info!!

[GraemeDeroux]

  What Mimosa said... 4-5 seconds at cure temp? That should do for a flash
but not a full cure. The backs held up better than the L/C because even though
the print was down, it still went through the dryer twice and the L/C only once. If
you can't slow the belt any more then at least run them through twice and start saving
up for a better dryer.

The back is what rubbed off. I printed the back then the front, so the back did go through twice and the fronts did not. The fronts stayed on perfect.

4-5 seconds at cure temp, I thought with Plastisol it just has to GET to 320, I didn't know it had to stay there. This is news to me!

[screenxpress]

I found this write-up at the Union Ink site.  It's probably similar for most brands -

Curing Plastisol Inks
Curing plastisol inks is a matter of exposing them to the proper amount of heat for the correct length of time. Correct curing of plastisol ink is extremely important. The most common problem encountered with plastisol inks is poor washability. In almost every case, this is due to incomplete ink cure.

When plastisol is heated, the resin particles absorb the surrounding liquid (plasticizer) and swell, merge with each other and form a tough, elastic film. It is generally impossible to overcure direct prints because the overcure temperature is above the scorching point of the garment. However, it is not recommended that you heat the ink layer above 350º F (176º C). Above this temperature puff inks fall like a cake when you slam the oven door, and problems with dye migration are greatly increased. If the entire thickness of the ink is not brought to the correct curing temperature the ink will be under-cured (the resin has not absorbed all of the plasticizer) and the ink will crack and flake off the garment when washed.

Temperature
Plastisol will start to become dry to the touch or gelled (also called semi-cured) between 180-250º F (82-121º C). It becomes fully cured between 280-320º F (138-160º C), depending on the type of plastisol. The temperature at which the ink becomes fully cured is called the fusion temperature. Most Union Ink plastisol inks cure at 300º F (149º C). Check the Technical Data Sheet for each Union Ink plastisol for complete instructions.

Measuring Ink Temperature
Temperature test strips are useful for determining temperatures of the printed ink film. For thick prints, a temperature tape should be placed inside the garment to make sure the proper temperature is achieved at the bottom of the ink film. Temperature probes and infrared thermometers (pyrometers) can also be used. Although they are extremely precise at measuring temperature, they may give erroneous ink film temperature readings if not used correctly because the probe may not react quickly enough to changes in the ink film temperature.

Time
Once the entire ink film thickness reaches the proper temperature, the ink is fully cured. This means that with a high enough temperature in the curing unit, the plastisol could actually be cured in a few seconds.

Here is the actual link - https://www.unionink.com/tips-techniques/general-info-plastisol-inks/

[Frog]

I originally had this dryer set to have an exit temp of around 400 and I was nervous I was actually torching garments. So I turned it down.

I am going to raise up the element, and slow down the dryer even more and do some tests. Thank you for this info!!

The back is what rubbed off. I printed the back then the front, so the back did go through twice and the fronts did not. The fronts stayed on perfect.

4-5 seconds at cure temp, I thought with Plastisol it just has to GET to 320, I didn't know it had to stay there. This is news to me!

How are you measuring? Just what is reaching 400? I suspect that that's just the surface, and the bottom of the layer never reached cure temp. It really does only have to get to 320, but that means ALL OF IT, COMPLETELY THROUGH TO THE BOTTOM! It is possible with a tiny 110v  dryer (for years I used a 4 ft. Scamp) but it will not always be  easy or consistent, and, may always have issues on the edges of full sized prints. I once worked in a shop that was using a half-assed DIY dryer, and I had to run 'em through, rotate 90 degrees, and run again. Not great for real production as you try to grow.
Another thing you may want to consider is adding low temp cure additive available from most ink companies.