# FLash Curing Question



## Hillhouse (Feb 12, 2008)

Hey everyone, I have a quick question on curing my final print with a flash dryer.
I had run a couple test prints of a design i am doing on pieces of fabric, in the design there are two colors, Red and Black. I flashed the red and then laid down the black. After that I moved it to another spot for the cure. I let my flash set about 5 inches above the print for about 45 secs. Now the print was dry to the touch, nothing came off on my finger. The black looked wet in some spots, but like I said it was dry to the touch. After that I took a corner of the material and rubbed it on top of the ink itself and it rubbed of kinda like it was powder. I know that sound weird but that is what it did. I then threw them in the washer for a bit and after I took it out, the black had been smeared all over that piece of material, but the image was still there. It was as if the top layer of ink had not dryed or something. O and by the way the red was completely fine, didn't do anything. So my question is, did I not leave the flash over it long enough or does it have something to do with my ink...? Can your double cure also, so let's say I cure the final print for 50 sec. or so, let it cool down and then do it again, just to make sure that it is cured completely. I know it sounds like a lot of time, but that isn't my concern. I am just doing a few prints, so I got all day....
Anything will help, thanks


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## kriscad (Dec 18, 2006)

im confused... so you dont have a dryer to cure the ink right?


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## snarley (Feb 9, 2007)

Hi Devin,

The important thing in curing plastisol ink is to attain fusion temperature 280-320 degrees Fahrenheit, depending on the type of plastisol used.

Plastisol will start to become dry to the touch at 180-250 degrees Fahrenheit, which is what you do when you Print-Flash-Print (PFP) on multi-color jobs that require it.

Many screen printers use Flash-Cure units to fully cure shirts everyday. On your smaller conveyor dryers they use the same infrared heaters that are in the flash-cure unit.

The thing is to fully cure your ink, it might feel cured but if it doesn't reach fusion temperature it will probably crack or flake off when the garment is washed.

You might want to try using paper thermometers (heat strip). These heat-sening strips turn black at what ever temperature they reach, they are sold in 6 different heat ranges and are sold by many screen printing suppliers. They also have heat temperature guns that measure the surface tempertature of the ink, they are cheaper in the long run as you don't have to keep buying the strips.

You will never be able to achieve a high production output using a flash-cure dryer for curing your final product, you should consider getting a conveyor oven when you need to speed up your production cycle.

I hope this is of some help and good luck on your printing.

Bill m


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## jeffie (Jan 30, 2008)

Hey, well said Snarly...jeff


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## Hillhouse (Feb 12, 2008)

Snarly, Thank you so much.... This is going to help me out huge...
I know a conveyor is next on my list of things to get.... just ran out of my money for now....

Thanks again


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## ieaturheart (Apr 2, 2007)

I have a quick question. What I was doing was after I printing the last color on shirt A then I would go about putting it under the flashing unit while I print the last color on shirt B then take off shirt A and put B under the flashing unit. 

If it stays under the flashing unit for a minute or even 2 minutes will the extra time hurt it. Like does there need to be a happy medium and once that temp range is reached then its done?


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## wormil (Jan 7, 2008)

Hillhouse said:


> I flashed the red and then laid down the black.


Are you doing that because you need to or because you think you need to? Usually you would just print red, then black, then cure. Although there may be times when you would print black then red.

To test your cure give it a good stretch sideways, if it cracks, it isn't cured.


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## marlo45 (Oct 4, 2007)

ieaturheart said:


> I have a quick question. What I was doing was after I printing the last color on shirt A then I would go about putting it under the flashing unit while I print the last color on shirt B then take off shirt A and put B under the flashing unit.
> 
> If it stays under the flashing unit for a minute or even 2 minutes will the extra time hurt it. Like does there need to be a happy medium and once that temp range is reached then its done?


I believe your only problem with up to 2 minutes would be the shirt burning, not the plastisol. You should be fine, i've done that a few times, albeit, totally unintentional. 

On average i keep my shirts under the flash unit for 1:15 - 1:30. So long as it hits that fusion temp like Snarley mentioned, you wont need to worry about the ink, you shirt will more likely start to burn before it does.


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## cutty21 (May 27, 2009)

hey everyone i jus had anuther unsuccessful day at printing shirts. i have a couple questions, first is how many coats of emulsion do most people put on the screen and second is how long do u let it dry before trying to expose your image? and 1 more i forgot about how long should i be exposing my image for?


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## BroJames (Jul 8, 2008)

cutty21 said:


> hey everyone i jus had anuther unsuccessful day at printing shirts. i have a couple questions, first is how many coats of emulsion do most people put on the screen and second is how long do u let it dry before trying to expose your image? and 1 more i forgot about how long should i be exposing my image for?


Lots of variables

You can really coat only 1 side, both sides, 2 coats on 1 side and 1 on the other, 2 coats both sides, etc. Depends on how thick you want or need the emuslion to be. However, 1 coat each side should be safe.

Drying time depends on your climate and the humdity. With an electric fan blowing 2 hours is more than enough. Some reported dry emulsion in less than an hour. With a hair dryer hovering closely above the screen or heat gun (about 15 inches away) it should dry in less than 30 minutes.

Exposure time depends on the type of emulsion, coating or thickness of the emulsion, the type of UV source and the watttage, the distance between the UV source and the screen, etc. For 500w halogens 12 inches high 3-4 minutes should be about right. UV fluorescents should expose most emulions in 1 minute or so.


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