Help!!White ink cracking on 100%- passing hard stretch on 50/50 and 100% poly??!

[acescreen]

Ok after doing this for about over 15 years I was stumped today!!!...... Just when you think you know a thing or two.....

We started a run this morning of 200 dark green shirts (PC54) with a full back logo 10" wide state of Texas image, white ink, print flash print (Workhorse Flashback) 123 mesh, curing them through an M&R heatwave gas dryer, oven temp set to 350* surface ink temp hitting 335-340* midpoint through the 8'6" chamber.
The first shirt my printer ran through was a test print 50/50, did our standard stretch test held up fine. Printer running solo, when I came out to get a size change, I stretched one and it easily cracked open, so I turn up the temp and slow down the belt. Ended up messing with it for a while.... slowed the belt even more, oven temp up to 365* and it was still cracking easily in some areas. So I figured bad batch of ink(local supplier private label we've been using for a few years) so I called my supplier and he brought me a different ink (Triangle Phoenix) which was our go to before we switched to his ink. We ran one shirt through with Phoenix and it passed the test... I figure problem solved, bad batch... so we started up the run again, came out to grab another size change checked it, cracks easy again!!!!!

We ended up slowing the belt down to a craw cranked oven temp up to 375* (first time ever that hot) and at the end it was still cracking on some shirts but not all shirts. At the end of the run I ran a 50/50, 100% poly, Bella Canvas 100% and a Gildan 5.4oz 100%. They all held up fine to the stretch test except for the PC54 and the Gildan 100% which still cracked easily???  I will be hitting all 200 with our heat press to ensure they cure to the shirt and to fix the ones we stretched out.

I noticed that the ink on the  poly/blends was hitting higher temps than the 100% shirts. Which may explain a little but the 100% were still getting to the 355* range crawling in the chamber and then still cracking???

Please let me know your thoughts.

Also can you guys running gas dryers let me know what temp/speed you are running shirts. I know everything has it's variables and is specific to the shop and area. We just switched to gas less than a year ago and I was just getting comfortable and confident in my settings and now I feel like I'm lost.

Thanks in advance guys!

[Doug S]

With our mini sprint 8' chamber I on average run it at 390 with a belt speed of 16 for underbased shirts and 18 for non-underbased.  With the exception of 100 poly and then I'll bump the speed up to 25 and the temp down to 360.   I did however turn the speed down to 14 to cure some metallic silver.   Like you said though it will be different at different shops.

[Screen Dan]

I can't comment on the rest...it is perplexing and I have no idea.  But I do know that our 2 Sprint 2000 HOs, 8 segments...forget how many feet of heat that is,   I think 12 plus with ~6ft infeed and outfeed each.

Our temp is set to 385 for a target temp a ~375, 22f/m belt speed, which could go up or down ~2f/m depending on if discharge or HD plastisol, etc.  It has been set like this for over a decade now and has worked without fail...for us, in our shop anyway.  No cracking, full cure, very long lasting wash-safe prints.  QCM inks.

[screenprintguy]

We never set our heatwave that low accept 100% poly shirts. Surface Temps always need to be hovering around 350-360 for a full cure on cottons. When we did the donut temp tests, any surface Temps on cotton that were around 330 were below 300 at substrate level, so obviously the surface temp test will give a false reading for full cure. So for cotton,  we set our heatwave at 375, speed 2.8.

[Colin]

Sprint 2000HO
12 foot chamber
330 degrees
12 speed

Sounds like you may have a blockage in your air chambers/air knives that push the heat onto the shirt.

Do you see a difference on either side of the dryer?

Just a random guess on my part

[cleveprint]

48" sprint with 8 feet of heat here. i had a similar problem when we first got it. had an order of 80 hoods come back completely cracked and washed off. needless to say, we have been testing like crazy since then! since then, ive found that 375 with the belt at 12/13 seems to work for us. poly stuff we have been at 320 with the belt at 16. so far so good, but always trying to stay on top of it.

[mimosatexas]

Are y'all relying on the dryer to tell you the temp of the cure?  I laser temp as they are in the chamber on every run.  If the temp is good on the test prints, I start my run, and on longer runs will laser temp periodically to make sure nothing is fluctuating.  Haven't had a washed out plastisol print come back to me yet and I use lots of random test print shirts as shop shirts so they get wash tested as I wear them too.

[cleveprint]

yeah we have a laser gun and i finally bought a donut too. laser on every job to be sure. the donut maybe every few days just to be safe. but i feel like we are pretty dialed in now.

[mimosatexas]

There is just no way I would trust some dial on the dryer to tell me the exact temp of the shirt.  Different colors and materials heat differently.  Laser tells you what's up and takes a few seconds at most.

[screenxpress]

Are y'all relying on the dryer to tell you the temp of the cure?  I laser temp as they are in the chamber on every run.  If the temp is good on the test prints, I start my run, and on longer runs will laser temp periodically to make sure nothing is fluctuating.  Haven't had a washed out plastisol print come back to me yet and I use lots of random test print shirts as shop shirts so they get wash tested as I wear them too.

What he said

[acescreen]

Thanks for the responses guys. Just to answer a few questions/comments...yes we always laser temp our garments on every run and in between/during runs on big jobs or busy days. Air flow seems fine but I still took a close look and cleaned up the filters, exhaust fan box, etc. Lots of air moving in the chamber and exhausting out the dryer. Like many of you mentioned I wear my shirts and I wash them and I don't think we've ever had an order returned due to ink washing out, as a matter of fact a customer came to order camp shirts for this summer wearing the shirt we did last summer and it looked like it did when it left our shop. 3 color prnt with 2 white coats on a 50/50 camo shirt. 

After making and getting calls and doing a ton of research these last few days here is what I got from this ordeal:
Sorry for the book, but I wanted to share details as I have learned tons from detailed posts I've found on here)

OVEN TEMPS:  Sounds like most of you gas guys run that chamber way up there in the temp range. I tried running yesterday @ 375 and the inks were coming out at 380ish and the shirts were so damn hot you could hardly touch them even at the end of the belt and tags were shriveling up. So that for us is way too hot.  I ran a 6 color with a base white on Gil 100% and took the oven temp down to 360, ink surface temp came out about 355, stretched it pretty hard and it held. I ran some 50/50's at 360 and the ink surface temp was up to 371 and shirts would scorch your finger tips, so I went back down to 350 on those ink surface temp was 355ish , stretched it and it held great. All speeds were moderate not fast at all but not crawling. The shop I used to work at has a Sprint 2000 and he said they never set it past 345. Also Colin commented on this thread he is running at 330 with a Sp2000...I got a call from someone yesterday that said most people are running way too hot and it could be over curing the ink. He mentioned over cured inks will crack just like under cured. We talked about how most manufactures inks gel/cure at about 300 but they ask for 320-330 to cover their ass.
So I think we all agree there is no magic number, different oven temps and belt speeds for different garments and every shop will be different. Hell I wonder if there are properties in the gas that we all get from different suppliers that would effect how hot the flame burns effecting the oven temp??? 

GARMENTS: I took that PC61 dark green shirt that started this whole thing and washed it and it held up fine. Stretched it after the wash and it still cracked some??? I ran one through the drier yesterday at 375 2 times at a craw stretched it and it cracked??? So is this the weave of the shirt that is opening up too easy, is the weave so open ink is getting pushed too far into the garment making it more prone to cracking when stretched? (My print pressure was not too high) Also keep in mind some stretched out and some cracked with a light tug??  I know not everyone sees the stretch test as a cure test either so is this one of those garment/ink variables that will always crack when stretched? In the end for my own piece of mind we hit them with our transfer machine and after that they wouldn't crack on a hard pull.

Retail Store test: (my wife hates when I go around doing this) I went to a retail store here locally that evening and went on quality/stretch test rant as I'm sure many of us do. I was only checking darks with white plastisol ink. I tugged on a few Cowboys shirts(100%cotton) with a star logo (2 whites) that cracked easily, tugged on a few Spurs shirts (100% cotton) with a very thick white that would not crack no matter how hard I pulled. Found a USA vs Mex soccer shirt on a premium Next Level tank that damn near cracked just by taking it off the hanger!  Too my surprise all the 100% poly dri fit stuff would not crack, all of the 50/50's would not crack unless pulled on really hard. The only shirts that I found that would crack easily were all 100% cotton shirts (to clarify not all 100% cracked easy but any shirt I found that did was 100%). That's weird that's the exact pattern I'm finding at my place.

Conclusion: (white inks on dark shirts)
*Stretch test is not the end all be all of a cure test
*100% poly and 50/50 garments- prints will stretch much better than 100% and also they get much hotter in the chamber
*Economy100% cotton tees- looser weave, prints have more tendency to crack when stretched, run cooler in the chamber
*100% cotton premium/ringspun- tighert weave, prints hold up better it takes more stretch to crack

Let me know what you guys think of all this and what you have found in your testing. I know it's something that we all have to stay on top of and check on a daily basis. So the more we share the more we can try and control all these crazy variables. Hope this helps more than it confuses people. Thanks guys.