Why do my cards bend? Demystifying humidity

Invited Article | Author: Mr D
IG: dtcg.photography

In humid Singapore, we've realized that the recent foil cards bend very easily. In particular, our delay option cards from ST7/8 was bent out-of-the-box. This is not only an aesthetic issue, but was felt by many as a somewhat "unintentional" cheating mechanism in tournaments. 

With the recent updates in ST7/8 and BT-06, rare cards are now given the foil treatment as well. Seeing a much larger stash of cards bending in natural humidity has motivated our fellow collector Mr. D share his insights on card humidity.

Sistermon is bent 🙁

Why do my cards bend? Demystifying humidity

Imagine that you have just pulled a [BT5-112] Omnimon Zwart Defeat Alternate-Art from a box. Happily, you sleeved it up with your KMC Perfect Hard sleeve and placed inside your zipped binder (or your acrylic brick) and had a wonderful dream that night. A week later, you open your binder to find a slightly bent Zwart Defeat!

From different kinds of sleeves to the placement of your binder (vertically vs horizontally), topics surrounding on “how-to” or “the-best-way” to protect and store TCG cards have always been a thing in the TCG community. Today, we will look into one of the most crucial factors in storing TCG cards – the culprit behind the aforementioned story – humidity. 

We will discuss on:

    • Part 1: The things you need to keep humidity in check:
      • A moisture absorber
      • A tightly sealed storage box, where you will keep your cards with the moisture absorber
      • A hygrometer
    • Part 2: Humidity and cards
      • How do DTCG cards react to different humidity? (With pics!)
      • Can you unbend bent cards?
      • What humidity is good for DTCG cards?

Part 1: The things you need

Moisture Absorbers
Moisture absorbers are everywhere – on every shelf of any supermarket or health/beauty retail shop. It is especially ubiquitous in the country we live in, with a daily humidity of 70-80%. The most common type of moisture absorbers is the lid-covered non-reusable box.

The other type we recently found out is the Deerma Mini Dehumidifier by Xiaomi. It is reusable – by charging it to dry up the in-built silica gels once it becomes humid, and the price is quite reasonable (USD$20 on Amazon US). 

We tried out both moisture absorber (more pics in part2). In short, we would say both are equally good in keeping the air dry enough, which is around 45-55% humidity. In terms of cost, one lid-covered moisture absorber costs around USD$1~$2 and it can last around 1.5 months in our case (subject to your environment’s humidity, and how often you open your box. Our place has a humidity score of 75%). A Deerma Mini Dehumidifier is around $20, and it needs a recharge to dry up the beans every 2~3 weeks. Compared to the lid-types, this is more environmental-friendly (less disposables), therefore we would recommend the Deerma’s over the lid-types.

Storage boxes

Storage boxes are as important as moisture absorbers. They are where you keep your cards, deck boxes and binders, together with your moisture absorber. A tightly sealed box ensures the dry air stays inside the box, thus making sure of the effectiveness of your moisture absorber. We tried with the common “side-click-and-lock” box, and it just doesn’t work. The humidity inside the box does not drop at all, and our Deerma Mini Dehumidifier needs to be recharged after just one night

We suggest using the “top-all-round-seal” kind of storage boxes (as shown below), where you literally need to press all corners to properly close the lid.

Storage boxes

You can find hygrometer anywhere as well. We wanted a “smart” hygrometer, where the humidity readings can be observed via a phone app, or to send us a notification when the humidity exceeds certain level so that we know it’s time to recharge/change our moisture absorber. We got the Xiaomi Mijia Bluetooth Thermometer with Hygrometer. After connecting with Mi Home app, you can read the temp/humidity readings from your phone. They also keep a history of the readings!

Part 2: Humidity and cards

In this part, we show some of the observations we made on DTCG cards when humidity is too high or low, and what is the good humidity that we personally think, based on observations on the cards.

A simple google gave us some insights on the r/MTG community’s opinion on the optimal storage humidity:


And so we plan to test on 3 different humidity levels:

    • Humid: 75% (which is our room’s default humidity)
    • Dry: below 30%
    • Optimal: 50%

Our setting is as follows:

    • A foiled DTCG card: Normal art BT2-066 Machinedramon. The card has been sleeved since pulled and kept in the drawer for a few months.
    • Storage box
    • Hygrometer
    • A moisture absorber
Humid (75% humidity)

The card was kept in the room without any desiccants, so it had been subjected to high humidity for a period of time. The foiled part is the artwork, while the back of the card is non-foiled. The red line is a drawn straight line. The picture below is a sideview of the card, as you can see, the card bends/curls towards the foiled part

Optimal (50% humidity)

For optimal humidity of 50%, we use a newly opened lid-type moisture absorber. In order to slow down the moisture absorption rate (if not it will drop to 20% in like few hours!), we remove half of the aluminum foil instead of the entire covering. Then we put the foiled card, the moisture absorber and the hygrometer into the storage box and cover it, as per mentioned in the setting above. Since we want to observe the long-term effect of cards under this humidity, we let it settle for 5 days. Occasionally, we will open the storage box to mimic the scenario where we usually open the storage box to take or put something.

The 5 days average readings are shown as followed:

Seems like the humidity is kept well although we opened the lid at least once a day. And the card looks straight now

Dry (<30% humidity)

After the previous experiment, we then fully remove the aluminum foil cover of the moisture absorber. We also aired the box to revert the humidity back to room humidity (75%). With the same setting, this time we put the card in the box for just 12hrs.

Left: For just 4 hours, we can see that the humidity is dropping real fast.
Right: The next morning, it is already at 28%. Afraid that it is too dry, we took the card out.

The card now bents in the opposite direction compared to when humid.

From the 3 humidity observations, we would suggest that a humidity of 45-55% is good. And if your cards are bent due to the humid environment, you can always “bend” it back by putting it in a dry environment for a couple of days. Take note: Do try out with your inexpensive foil cards before doing it to your prized cards. 

Final thoughts

As collectors, it is always fun to learn how to protect and store our collection of cards. Humidity has always been the culprit behind many bent cards, especially in tropical climates. We hope that this article is able to shed some light on humidity and its effects on Digimon cards. 

Do let me know if you have any queries, as I would be glad to share my experiences with you!

2 thoughts on “Why do my cards bend? Demystifying humidity”

  1. Excellent post, thanks for taking the time to share this, it has helped me a lot. I live in Costa Rica, a tropical country and it is tedious to see how my cads are folded with so much humidity.
    I am considering buying a dehumidifier for my entire room but i don't know if it will have the same results, if it can control the humidity as well as in the storage box with the moisture absorber, what do you think is better?
    by the way, sorry for the level of my English, I'm not good at all.

    1. Hi, thanks for the reply! I would not suggest buying an electric dehumidifier if that's what you mean, since the cost will be relatively higher when compared to the reusable ones. Smaller ones are easy to control, some cards need dryer air to "straighten" them, while some just need slightly dry just to make sure it doesnt bend. The foiling changes to across BTs, it's hard to have one for all I think.


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