How Humidity Affects Sublimation

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The intention of this article is to provide straightforward advice on how humidity can affect the sublimation process. I will specifically address its effects on the printing and heat press process of sublimation.

I first encountered this phenomenon when I thought I had my three pillars of heat pressing—temperature, pressure, and time—perfectly calibrated. On one particular day, all my pressed sublimations were turning out flawlessly. However, the very next day, I noticed a significant drop in quality. The results weren’t quite the same, despite no changes in my core settings.

I noticed that the lighting in the room was darker, which led me to consider the rainy weather outside as a potential factor. The day before had been sunny, and the difference in weather made me wonder: could humidity be the culprit? If so, it meant that regular calibrations would be necessary to compensate for these fluctuations.

The Science of Humidity and Its Impact on Sublimation

Ok. we know humidity is the concentration of water vapor present in the air, but how does this play a role in the sublimation process? It can significantly impact the heat pressing procedure, the materials used (substrate) and the printing of ink on sublimation paper. Here’s how:

1. Fabric Quality: Fabrics used in sublimation, such as polyester, can absorb moisture. High humidity can make the fabric feel damp, which affects the transfer process. The presence of moisture in the fabric can prevent the sublimation inks from penetrating deeply, resulting in a less durable print.

2. Ink Bleeding: High humidity can cause sublimation inks to bleed. When the air is too moist, the inks don’t dry as quickly as they should. During heat pressing, the excess moisture can cause the ink to spread beyond the intended design boundaries, leading to blurred or smeared images.

3. Color Shifting: Humidity can also alter the colors of the sublimated image. High moisture levels can affect how the inks transfer and bond with the substrate, resulting in colors that are less vibrant or shifted from their intended hues.

4. Ink Absorption Issues: High humidity increases the amount of moisture absorbed by the sublimation paper. This excessive moisture can interfere with the paper’s ability to absorb and hold the sublimation inks properly. The ink may spread out more than intended, leading to blurred or fuzzy prints. Not only that, the paper can curl up due to the moisture and hit the printer’s print heads.

5. Ink Drying Delays: In humid conditions, the inks take longer to dry on the sublimation paper. This delayed drying time can cause smudging or smearing if the paper is handled too soon after printing. It can also result in poor transfer quality during the heat press process and lead to premature cracking and peeling of the print.

Troubleshooting The Humidity Issue

One of the easiest and effective things you can do is to suck all the moisture out of your substrate. This is done by pre-pressing the fabric for a few seconds to remove excess moisture. The fabric should be dry enough ready for sublimation.

But what about humidity on sublimation paper? Higher quality sublimation paper have better quality coating to handle moisture, I would recommend using these. If for whatever reason you have already printed your design on the sheets but need to store them for a while, consider purchasing teflon sheets and place them in-between the sublimation paper to prevent moisture from getting to them.

Lastly, as always, perform test prints when there are noticeable changes in humidity to adjust the color profiles and ensure accurate color reproduction.

Conclusion

When I figured out that humidity was messing with my sublimation prints, I had to sacrifice a few substrates and tweak the temperature, pressure, and timing until I got it just right. Pre-pressing the fabric before printing also made a difference.

The recommendations provided in this article are for places with high humidity. Luckily, where I live, the humidity doesn’t that change significantly, so I don’t have to worry about it too much. But if you’re in a more humid area, these adjustments will help improve the quality and durability of your prints. Just keep tweaking until you get a feel for what needs to be done depending on the humidity levels!

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