Curing is sometimes an overlooked aspect of screen printing and the printing process, but it is the most vital part to ensuring the longevity of your print designs.
This article will focus mainly on water base ink curing – or should I say drying – as Matsui International is an exclusive water base ink producer, and water base ink simple evaporates. Since we are on the topic though, plastisol “cures,” because plastisol ink is in essence plastic in a liquefied state due to a plasticizing agent. Instead of evaporating, plastisol inks vary, but approximately only 1% of the ink is burned off through curing and the remaining ink rests on top of the fabric. Drying water base ink is simple enough, but I want to go thoroughly deep into all the details and specifics of how to get the perfect cure with anything, anywhere.
Water base ink can in truth, dry completely out in the sun, but I wouldn’t recommend it, it takes excessive amount of time and can beat up your garment, making it rough and fading it, which will yield poor color fastness and nobody likes a sun-beaten rough garment.
The foundation of drying / curing in screen printing starts with infrared heat panels. These are what exist in flash dryers and conveyor dryers that actually dry your inks. Smaller screen print operations often only have flash dryers for curing and this can be done, but the margin for error is thin, using a plug-in infrared panel or blow dry type heat gun are even more questionable forms of drying that will yield many garment casualties. Because of this, I recommend at least a flash dryer, especially since these are extremely useful for printing on dark garments with laying done white under-bases to increase color opacity and vividness. Ultimately, everyone will recommend a conveyor dryer as the ideal set-up with a flash dryer as a supplementary essential item. Conveyor dryers have a mesh knit fabric that is rolled on a conveyor belt through an enclose area, creating its own controlled micro-climate, delivering the most consistent cure.
Within conveyor dryers there are gas and electric dryers, much like lawnmowers, gas dryers tend to be more reliable and effective, but, nevertheless electric dryers are preferred for their clean energy source and economy. Gas dryers are more desirable because Electric Dryer’s interior infrared heat panels tend to be more problematic with small fluctuations in temperature that can lead to inconsistent curing, these sometimes erratic fluctuations in temperature will often not be shown accurately on your electric dryer temperature display.
These changes can be caused solely by fluctuations in electric powering being transmitted to your dryer, but it is often a combination of conditions where you are screen printing and drying that are also having an effect on the accuracy of your curing. Gas and electric dryers are both susceptible to changes in temperature at your location, if it’s a closed air room or an open air warehouse etc., the overall humidity, if there’s any wind getting inside the dryer etc.
The severity of these conditions can vary greatly, usually not effecting your drying significantly, but at other times your conditions can make the entire printing process quiet difficult. One key note to remember is that the humidity level where you are printing should always be above 35%. This is an issue that usually only effects extremely dry climates such as deserts.
If you are in a severely dry climate, it might be useful to consider getting a hygrometer which will accurately inform you of the humidity and temperature, they are very cheap online. In the case that you so happen to be below 35% humidity, a simple humidifier may not suffice, we recommend getting a portable evaporative cooler, also known as, a swamp cooler. These devices operate as humidifiers and coolers for large areas.
Heat Guns are also another option for verifying the conditions within a conveyor dryer. They utilize lasers to notify the temperature of the exact spot the laser is targeted at. These devices are fairly reliable, in most cases giving you a good indications if your dryer is close to the desired temperature; however these devices are fallible to a certain degree because laser technology captures the movement of particles in the air in the exact line the laser is targeted at. It is accurate, but not exact.
This leads to the next device, the more precise donut probe, made out of ceramic with two metal cross-hairs that you should rest on the thickest part of the ink. It is of the utmost importance that you place the donut probe at the thickest part because the interior of the thickest section of the ink must reach 320°F for 3 minutes. It is like the analogy of cooking a steak, you can’t cook it on too high of a temperature or else you’ll burn the outside and have a rare inside. In order to cook it throughout you must lower the temperature to a more moderate heat and increase the cooking length of time.
The final accessory to assist in a proper dry is temperature strips, these being the least reliable accessory to inform screen printers of the temperature on their ink when drying. They are very affordable, but truly function as a temperature threshold indicator, notifying screen printers if their dryer simply has reached or surpassed a temperature – even with these certain limitations, they are not a reliable product that any screen printing business should be relying on for high quality consistent prints.
All of the listed factors and tools can contribute to a proper or poor cure of screen printing ink. One last thing that should be stated is if you happen to ever be the end-user of a screen printed item that wasn’t fully cured, you can always throw it in the dryer at the highest temperature setting and that can increase the color fastness and longevity of your shirt. It can improve an improper cure and greatly increase the life of a print.
I hope all these details can make a difference in your quality of prints and product. Thank you for reading.