T-Shirt Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
32 Posts
Discussion Starter #1
Help me please. I have been using my flash to cure out shirts since I started a few months ago. I just received a call telling me that the ink fell off of a shirt after the second wash. I remembered having one of that particular order left over and washed it to see for myself and the ink did indeed come off in some spots.(Only on the white ink though) I have my flash set at 2 inches and cure for 1 minute. If I leave it any longer the shirts start to smoke really bad. Any clue to why this happened only to the white ink???
 

·
Registered
Joined
·
815 Posts
Get a laser temp gun and make sure all your shirts are cured to 320 degrees, don't mind the smoke a little smoke is okay!

I have cured with my flash without issues this way.
 

·
Registered
Joined
·
2,919 Posts
How thick is the ink? If you're printing white ink on darks, and you're really loading up the ink with print/flash/print it's possible that the ink at the bottom isn't curing completely. And, a flash unit will often leave the ink around the perimeter of the design cured less than that in the middle. A stretch test will help determine cure, but with a flash you're going to have to make sure the entire design is cured all the way through . . . not just the part in the middle where it's hottest.
 

·
Registered
Joined
·
9,534 Posts
Tom, how many seconds would you recommend the ink to stay at say 320F?

I have read that 25-30 seconds (more or less) under a heat press is ideal but some people claim plastisols can be cured in 10 seconds I think. I am sure that the recommended dwell time of commercial conveyor dryers is much higher than 10 seconds.

This post in another thread says 45 seconds
Yes, you can cure plastisol with a flash dryer. We recommend the unit to be 3" off the garment and leave it under for 40-45 seconds. This is an estimate, it may take longer by a few seconds or shorter as the shirt board heats up.
Plastisol needs to reach 320 degrees to be cured. That time frame should get you there. It is best thought o have a temp gun to make sure you are getting to 320 degrees.
Source: http://www.t-shirtforums.com/screen-printing-equipment/t82554.html#post487003

One reason why I am asking is that my 4 year boy has a pair of pants he likes and has worn for several months. It is an image of a pair of rubber shoes and the plastisol inks were quite thick. It sayted fine after several washes but just a couple of days ago, the prints cracked up bad. Is that a case of undercured prints that appears to be cured?
 

·
Registered
Joined
·
66 Posts
Hi,

the ten seconds on plastisol inks is used as a quick cure between different colours. Usually I dry mine at around 6inches high, for 120 seconds for a complete cure and this seems to hold fine.

As with all things its practise practise practise until you get a rough feel of how powerful (hot) your flash dryer is and how long it requires to dry. I think two inches is a bit close and this is the reason you are burning the shirts...

hope this helps..
 

·
Registered
Joined
·
2,919 Posts
Depends on the flash. If you don't have an off-contact thermometer, about all you can do is do a stretch test and, ideally, a wash test. Most plastisol ink manufacturers will have a disclaimer about their ink washing off, advising a wash test prior to printing.
Like I said earlier, the biggest problem with using a flash is the edges of the print get less heat than the middle. The middle will almost boil by the time the edges get hot enough to cure, and if there's a draft in the area of the flash, that can have an influence.
 

·
Registered
Joined
·
9,534 Posts
Hi,

the ten seconds on plastisol inks is used as a quick cure between different colours. Usually I dry mine at around 6inches high, for 120 seconds for a complete cure and this seems to hold fine.

As with all things its practise practise practise until you get a rough feel of how powerful (hot) your flash dryer is and how long it requires to dry. I think two inches is a bit close and this is the reason you are burning the shirts...

hope this helps..
Just curious. Why 6inches? It seems pretty high unless curing waterbase or to cover a larger area. Or is it to give the heat enough time to penetrate into the ink without overheating the outer film?

So 10 seconds or so under a BBC Blackbody 14x14 flash cure seems like an undercure? Some people insisted they are not but when the plastisol print on my son's pants cracked after being worn (and washed) for several months it does seem that some people have been unintentionally undercuring their plastisols.

To repeat the TJ Ryonet Tech quote above, with the flashcure set 3" above shirt, it will take about 45 seconds to full cure plastisol prints. In relation to the thread starter's problem, a 1 minute curing time should be enough unless the temperature is set too low or some other problem like cold spots. Time and temperature should be inversely related.

And while on the issue of curing temperature and time, I just searched some videos on youtube summarized below for reference:

With a 750F setting on the "face of the heater" 2-1/2 inch above the shirt, Vastec suggested 25 seconds dwell time. The measured ink temperature is 370-380F on their Econored II full fledged infrared conveyor dryer. Source: [media]http://www.youtube.com/watch?v=fHz-zYVEtCQ&feature=related[/media]Workhorse recommended 45 seconds under a 320F setting(330-340F ink reading) on their dedicated quarts conveyor dryer. Source: [media]http://www.youtube.com/watch?v=PJoeiavaUDQ&feature=related[/media]I believe the the same temperature/time settings are about correct for other powerful 10,000-20,000w infrared dryers. And, 1-2000w flash cure units should not be expected to do better.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #9
I am using Union low bleed plastisol ink. I didn't buy a temp. gun because I watched a video by a silk screening consultant and he claims they are not accurate in stating that the gun actually reads the ambient temp between the substrate and the gun itself, Not the actual substrate. He did this by checking the temp of an ice cube and holding it while turning on a top burner in between the ice and the gun. While the red dot was on the ice, the temp rose to 98% in seconds. I'm new to this so I figured he knew what he was talking about.
I have used the stretch method to make sure the ink is dry and it seemed to work until now. Now because I just started , I only have one flash dryer so I use that for a final cure station and use a blow dryer in between as a flash. Could that be the problem? If so, why does the stretch test seem to work until they wash it?
 

·
Registered
Joined
·
2,919 Posts
The non-contact thermometer is supposed to read surface temperature. It won't tell you the temperature of the ink at the bottom of the ink layer, so you've still got to make a judgement call. Personally, I check the ink just before it's coming out of the dryer, and aim for an average of about 320 - 330. On the other hand, my dryer isn't running really fast, and I print with as thin an ink layer as I can get away with, so I'm reasonably sure it's cured, plus I do a stretch test. So far I've not had ink wash out. I also like to keep the ink as low as practicable to help minimize shine.
 

·
Registered
Joined
·
1,925 Posts
Use a professional laser thermomether (the one that is used in health care for measuring body temperature) to get accurate readings. And buy a conveyor dryer as soon as you can afford one, flashes aren't really the best way of curing.
 

·
Registered
Joined
·
173 Posts
I only have one flash dryer so I use that for a final cure station and use a blow dryer in between as a flash. Could that be the problem? If so, why does the stretch test seem to work until they wash it?
Do you mean a heat gun instead of a blow dryer? If you are using a heat gun its possible that you are over curing the first layer of ink. If the bottom layer of ink is cured the 2nd layer of ink will come off in the wash.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #14
Not a heat gun but hair dryer.I got that idea from another youtube video. It wasn't just the top layer coming off but all the white ink in some spots.
 

·
Registered
Joined
·
160 Posts
I am using Union low bleed plastisol ink. I didn't buy a temp. gun because I watched a video by a silk screening consultant and he claims they are not accurate in stating that the gun actually reads the ambient temp between the substrate and the gun itself, Not the actual substrate. He did this by checking the temp of an ice cube and holding it while turning on a top burner in between the ice and the gun. While the red dot was on the ice, the temp rose to 98% in seconds. I'm new to this so I figured he knew what he was talking about.
I have used the stretch method to make sure the ink is dry and it seemed to work until now. Now because I just started , I only have one flash dryer so I use that for a final cure station and use a blow dryer in between as a flash. Could that be the problem? If so, why does the stretch test seem to work until they wash it?
Well thats just dandy. Two problems with this "expert".

1.) How many of us cure with a burner between us and the substrate?
2.) Most (not all) flash dryers heat using IR (infra-red) radiation. IR does not heat the air between the drier and substrate. So if the temp gun was reading the ambient air temp it would show room temp all the time.

If you're using an IR flash drier with a laser temp gun and the laser spot is on the shirt then its telling you the temp of the shirt. At 3 inches off mine takes about 35 - 40 seconds to reach 320 at the edges of the print (I measure at the edges rather then the center). With a print put on with a 110 screen I'll let it go another 10 - 15 seconds to be sure for the ink thickness. When the flash comes off there'll be a whif of smoke and the fine smell of well aged and cured plastisol wofting through the air.

With that ... I've never had a print wash off.
 

·
Registered
Joined
·
173 Posts
is the ink only coming off around the outside edges of the design? Keep in mind that if your flash dryer is 14" X 14" it would only evenly cure about a 12" X 12" area.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #17
Thanks Tom. Guess I shoulda known better.... Like I said I'm new at this. But I'm still puzzled as to why the ink stretched fine without cracking and still washed off.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #18
Ink "D"... Yes, it was the bottom part of the design. My flash is a 16x16 and the design was 14x12.
 

·
Registered
Joined
·
9,534 Posts
Thanks Tom. Guess I shoulda known better.... Like I said I'm new at this. But I'm still puzzled as to why the ink stretched fine without cracking and still washed off.
It has been said before that a stretch test does not meant a full cure. It is one indication though but not a guarantee.

Using a 1500w halogen I was able to cure plastisols in 5 seconds or so. That is if we define a cure as passing the stretch test. But after the wash test, some parts come off. For that reason I went back to using a 500w halogen worklamp to cure more slowly. I would presume that the heat have more time to penetrate the upper layer and cure through the entire plastisol print. I would think that this is the reason why some people, and I think this includes the owner of BBC flash dryers, do not recomment using a flashcure for curing - because it cures only the top layer. In contrast, an enclosed dryer or oven can contain the heat more effectively so the curing is not only from the top. The heat from the sides and from the bottom may not be as hot(high) as those from the top but it should help the top heat penetrate into the ink. I may be worng on this but I do think this is the reason why experts recommend the use of conveyor dryers.
 

·
Registered
Joined
·
9,534 Posts
Thanks Tom. Guess I shoulda known better.... Like I said I'm new at this. But I'm still puzzled as to why the ink stretched fine without cracking and still washed off.
It has been said before that a stretch test does not meant a full cure. It is one indication though but not a guarantee.

Using a 1500w halogen I was able to cure plastisols in 5 seconds or so. That is if we define a cure as passing the stretch test. But after the wash test, some parts come off. For that reason I went back to using a 500w halogen worklamp to cure more slowly. I would presume that the heat have more time to penetrate the upper layer and cure through the entire plastisol print. I would think that this is the reason why some people, and I think this includes the owner of BBC flash dryers, do not recommend using a flashcure for curing - because it cures only the top layer. In contrast, an enclosed dryer or oven can contain the heat more effectively so the curing is not only from the top. The heat from the sides and from the bottom may not be as hot(high) as those from the top but it should help the top heat penetrate into the ink. I may be wrong on this but I do think this is the reason why experts recommend the use of conveyor dryers.
 
1 - 20 of 22 Posts
Top