Can plastisol be too hot?

[Maxie]

I've just been reading an old thread and Frog said the ideal temperature for printing plastisols is 70F
Our shop goes over 90 on hot summer months.     Can the Plastisol be too hot?

[Sbrem]

Our shop is routinely 90° to 95°, so I wouldn't worry about. In fact, in the two shops I've been in over the years, 18 years at one and the last 25 here at my own shop, it's always been miserably hot...

Steve

[Frog]

Note that the key word here is "ideal". Not sure what the context was at the time, but probably initially got this from Colin,
our resident former ink tech who told us that 70F was the reference constant for testing purposes.

[abchung]

https://printwearmag.com/features/print-without-additives

There is a graph in the above article by Mark Coudray.


Sent from my SM-G930F using Tapatalk

[mooseman]

keep im mind the chart referenced is degrees C so according to the chart at the transition line of unstable to stable the temperature is 35C or 95 F, and the apparent lowest viscosity is around  54 C or 130 F . In summary then we would most likely never get plastisol at it's optimun temperature or too hot based on viscosity as the standard. PFP situations we all know can bring some different results in ink characteristics but that is a different conversation.
print on!
mooseman

[Frog]

Here's a thread from April, interestingly, also started by Maxie.
After reading it, this current thread, and the article, one has to ask  "at what point in the process are we talking about?"
You have storage, testing, or temp during the actual printing after being worked in screens on hot platens.

[Maxie]

I'm talking about temperature when printing.
I am also interested in knowing if you still need to stir plastisol in a hot working environment.

[Frog]

I'm talking about temperature when printing.
I am also interested in knowing if you still need to stir plastisol in a hot working environment.

So, you've mentioned your shop's ambient temperature can be in the 90"s, have you ever stuck a probe into the ink sitting in the back of a screen during a run? (while the press is stopped, of course, LOL)

[Maxie]

No, does printing heat the ink?
Have you done this?

[Frog]

No, does printing heat the ink?
Have you done this?

Not only does the friction of printing do this bit, as the linked article explains, the heated pallets really have an effect.

[Maxie]

So we don't really know the temp of the plastisol we are printing with.
If we are flashing a lot it will be hotter, not flashing cooler.
We often set up the day before and print in the morning, we leave the plastisol on the screens.
I need to look more carefully to see if there is a difference between what we print early and what we print after everything warms up.

[Colin]

I have used a laser gun to check temps of new inks while running to figure out how they perform under stress/while cold/etc.

Standard Ink run temps will range from mid 80's maybe low 90's with a single flash and a low number of prints needed (100-300) - to upwards of 120-130 (sometimes more if no one is paying attention) on multi thousands of shirts with 3 flashes.  At this point utmost care is taken with flash speed to keep temps down.

We actively try to keep our board temps between 120-130 (when they get up to 135+ I start to really pull back on the flashes as I can.  Sometimes I cant due to the inks nature).  This ensures good flash characteristics. Hotter than that and it becomes painful for the press op and you get to a tipping point on ink gel if you are using fast flash inks.  Most white inks have "faster flash" characteristics.

Oh, we have an M&R press with rubber tops, not honeycomb, so they hold heat for longer periods of time.  Honeycomb will, of course, cycle temps faster.

Most Ink companies have a tech sheet that will tell you its gel/flash temp.  I find that I don't want to get within 20-30 degrees of that temp....

Hope this helps a bit Maxie.

[Prince Art]

I need to look more carefully to see if there is a difference between what we print early and what we print after everything warms up.

I have no technical expertise regarding ink temp. But if you don't have a discernible difference between strike-offs & first few dozen prints, and prints made later in the run, I'd be surprised. Not only does temperature affect ink viscosity (& therefore how it prints), the squeegee action on a small volume of ink is like stirring the ink a lot more than you do before you put it in the screen. Add factors like desirable ink build-up on the back of screens, and I almost always find that prints about 3-4 dozen pieces into the run are superior to the earliest ones. Conversely, if the run goes on for awhile, I find the pallets go from helpfully warm to uncomfortably hot, and then I start to see problems arise. Sometimes opacity of white starts to drop, most often the hot pallets start curing the ink buildup on the back of screens, causing sticking issues.