Flashing - split from Orange Ink Thread

[Frog]

ripcord, while underbasing may seem like a waste of time, printing something 3 times is probably more of a time waster...

That's true if you have a multi station press...For me it's extra work to print a two color job with a flash because I only have a single station...

You gotta be the last person I know still clinging to a press with only one station.
I still print manually, but the change from my single station Hopkins to a multi station press was like night and day when flashing.  really reduced cool-down time to avoid tacky prints sticking to the next screen as well as the occasional semi-cure in screen, an issue I had completely forgotten about until this thread. (Way cooler for me on a hot day as well)

Of course, you've already shown the biggest reason to change;
You are settling for a lesser method to get coverage on some jobs.

[Ripcord]

Well, being self taught (nobody ever showed me how it's properly done...) I've always been perplexed by flashing. Maybe my flash unit is too small, although it's 16 X 20" which I thought was standard... If I position the flash over a regular size print (maybe 12 X 10",) the center gets way hotter than the edges, so to keep the heat relatively even I need to keep the flash moving a bit from side to side. If I don't, the edges won't gel but the center will be close to full cure temp. I've always read that if you achieve a full cure on an underbase, the overprint won't adhere properly, but I do not know for certain if this is indeed true...

So if I was running a multi station press and just parked a shirt under a stationary flash, I don't think it would flash properly. Parts of the print would be cured too much. I might start a new thread about this because I've always wondered what I'm missing about this...

[Frog]

I think that if a 16" x 20" flash is not gelling a 10" x 12" print fairly evenly, the panel is suspect (or you are too far away, or you have drafts)

And, 16" x 20" is bigger than a lot of manual printers use.

[Ripcord]

I think that if a 16" x 20" flash is not gelling a 10" x 12" print fairly evenly, the panel is suspect (or you are too far away, or you have drafts)

And, 16" x 20" is bigger than a lot of manual printers use.

That's what I've never been able to figure out. I do keep it rather high, about 5" over the shirt, and I monitor it with an infrared thermometer. I've seen videos of flash units just an inch or so from the shirt, but then how do you measure the temp when it's that close? Or should I stop obsessing about flashing a print too much?

[Frog]

Well, you know that your gun is only good for relative readings and not actual temp. That said, what reading do you get? What reading would you get a split second after swinging the panel away? At five inches, how long is it usually over the image?
If I were you, I'd lower that sucker to about two inches and see how that works.

Are you also familiar with how the ink feels to your touch the way you have been doing it? That gives you an easily checked indicator.

[mk162]

5" is too high...think of it as a shadow...the further you move your hand from the shadow the fuzzier the edges...with your flash that far from a shirt your edges are getting "fuzzy"

bring it down...and honestly, I don't check the temp, too many heat waves bouncing around in there.  let you panel come up to temp and check it by time, or swing your shirt out and check the temp that way(it will drop a few degrees)

[Ripcord]

I was thinking that if it was lower it would indeed heat more evenly. My concern has always been that if I can't monitor the temperature because I'll be busy printing the next shirt, how do I know if parts of the image are getting too warm (or is that really an issue? I've never wash tested the theory that overflashing results in the overprint not adhering properly and don't know if it's actually true...) I have learned to tell the difference between a gelled print and a fully cured print, but once it's cured it's cured. I flash to 230-240 degrees and have found that that is just right for most colors.

(I know I sound kind of stupid...I've never worked at a screen printing shop before. Just bought all the stuff 12 years ago and figured everything out along the way...)

[mk162]

we are all figuring it out along the way...name one person in here that hasn't had a job come back or had to reprint because they did everything perfectly...

ok with flashing, what I would do is count, you are much better off this way than with a heat gun. it should be way faster for you as well.

[Ripcord]

I've been printing a two color job this morning with white as one of the colors (the green isn't an overprint, it's butt registered,) so I tried lowering the flash to two inches. It's not a very big print, only 9" wide so indeed it makes the flash seem more even...but the temp as I read it on the surface reaches over 300 degrees. Maybe I'll get a temperature control for my flash unit like I have on my dryer.

So, can you really not print over cured ink or is that something that has been repeated so many times that everyone believes it? It would seem that once in the dryer, the heated ink goes back to a semi liquid state, which is when the bond between ink layers and the final cure happens. I've never understood why it would make a difference if the underbase had been gelled or fully cured.

I think next time I print a job with an underbase I'll do an extra shirt as a test and fully cure the underbase with the flash. Then I'll wash it a few times to see if the color comes off.....

[Frog]

I've been printing a two color job this morning with white as one of the colors (the green isn't an overprint, it's butt registered,) so I tried lowering the flash to two inches. It's not a very big print, only 9" wide so indeed it makes the flash seem more even...but the temp as I read it on the surface reaches over 300 degrees. Maybe I'll get a temperature control for my flash unit like I have on my dryer.

So, can you really not print over cured ink or is that something that has been repeated so many times that everyone believes it? It would seem that once in the dryer, the heated ink goes back to a semi liquid state, which is when the bond between ink layers and the final cure happens. I've never understood why it would make a difference if the underbase had been gelled or fully cured.

I think next time I print a job with an underbase I'll do an extra shirt as a test and fully cure the underbase with the flash. Then I'll wash it a few times to see if the color comes off.....

1. Surface temp reading of 300 after how many seconds? How about less time? Some folks flash as little as 2 or 3 seconds even with IR panels after a job gets going and the boards are warm. I'm guessing that you may be in the 6-10 second range depending on distance. btw, a momentary surface temp reading of 300 with a gun may still be closer to 250 through the ink itself. On a full cure of 310, it's not uncommon to see a split second spike of about 390 with a gun.

2. Though, at the insistence of the custy, I have successfully covered old prints with larger ones, they tended to be thick and bulletproof.
Most ink instructions do warm about diminished adhesion on a fully cured underbase, and many printers will verify this. I think it is not an absolute, and different conditions will provide different results.