Maybe this topic is talked about more often than I realize and I simply haven’t been made aware, I dunno. In any event, I wanted to condense (ha..ha..I’ve got jokes….) some insights on the impact of humidity on your tarot cards.

Ever notice how a wooden door seems to expand ever so slightly in the hot summer months? Musicians are all too aware of how temperamental wooden instruments can get depending on the weather and the humidity. Paper products like your tarot cards are made of cellulose fiber (derived from plant-based materials, like bark, wood, and leaves). They’re porous, causing them to be highly sensitive to humidity levels.

Cardstock absorbs moisture in the air.

Cardstock is hygroscopic, which means the cards, by their chemical (alchemical?) nature, will try to maintain an equilibrium with its environment, which means it’ll absorb water molecules in the air and also release its water molecules out into the air, to try and maintain that equilibrium. The temperature, humidity, and the climate of the region you live in have more of an impact on the durability of your tarot deck than you may realize.

Humidity can weaken paper products.

Keeping your cards for prolonged periods in very humid conditions will weaken the paper core. Both high humidity and low humidity can have an adverse effect on the core of your tarot decks. Low humidity causes the cards to lose water molecules, shrink ever so slightly, and curl. This also causes your decks to get brittle. High humidity means too much water from the environment is getting absorbed into the cardstock, which can weaken the cards, making them more susceptible to breakage under a riffle shuffle. Whereas those who live in environments with 50% ideal relative humidity can get away with rougher handling.

Ideal relative humidity.

The ideal setting is 50% relative humidity (RH). You can buy a humidity gauge monitor for less than $10 (USD) and getting one wouldn’t just be for your cards, either; it’s for your own health, too. High humidity accounts for lots of health issues, like being more prone to fatigue, muscle cramps, exacerbates disorientation, and exhaustion. Low humidity can account for chronic skin, throat, and respiratory conditions. Those who suffer from eczema or asthma have probably heard from their doctors to get a humidifier. So being mindful of humidity doesn’t just help preserve the condition of your cards. It’s beneficial to your health as well.

Avoid shocking your cards with extreme temperature changes.

When you move the cards from a very cold temperature to a very hot one, or vice versa too quickly, the fibers in the cardstock draw in and then release moisture suddenly, which can cause your cards to be more prone to warping. Keeping the deck properly wrapped in materials that will serve as a buffer can reduce the shock to your cards.

Avoid leaving your cards out exposed to direct sunlight.

There’s this old folksy saying about not leaving your tarot cards exposed to sunlight that made it sound like silly superstition. But I’ve learned the hard way that there’s a kernel of truth to it.

There were a few times I didn’t put my cards away right after use and left them in a full tarot spread out on my reading table, which was next to a window, exposing the cards to direct sunlight. I left it like that for a couple of days, and when I returned, I saw that the cards had curled. Nothing extreme, but still. They definitely warped.

Why the tradition of silk.

You’ve probably heard the superstition of having to wrap your tarot cards in silk. In Renaissance magic, ritual tools were traditionally wrapped in silk. Let’s set aside the spiritual aphorisms and just talk practicality.

Silk has long been prized for its ability to regulate and maintain temperature equilibrium. Silk will absorb and transfer (in this case divert) excess humidity away from what it’s wrapped around, and facilitates whatever it’s wrapped around to better maintain equilibrium with the environment.

Also, silk naturally wards off dust mites, and 100% mulberry silk has innate antibacterial and antimicrobial properties. Thus, in terms of care and maintenance of your prized items, such as a tarot deck, wrapping them in silk does have some rational-based benefits.

Confirm humidity levels of storage spaces.

If you’re going to be storing away a box of your decks for the long-term, then you may want to double-check the humidity levels of that storage space.

Back in law school I had a cardboard moving box full of decks that I left in the attic of a barn and forgot about it. Years later when I retrieved that box, all the decks in it warped, where each deck now had an arch in it.

So if you plan on putting a box of decks away for long-term storage, really think about the humidity and the temperature changes of that location.

Likewise, if you’re storing away unopened, brand new decks as an investment, hoping to earn a profit in the future when the deck is out of print, then be thoughtful about where you store these decks. Humidity can deteriorate the condition of the cards inside the box.

Damp basements, for example, would probably be a terrible idea. Anywhere that gets too hot, too cold and has poor ventilation would also be risky. When I’m about to put down hundreds of dollars, sometimes even up to four digits, for an unopened out of print deck, I’ll ask questions about how long the deck has been in storage, where it’s been in storage, etc. to get a sense of whether the seller has been attentive to humidity issues.

How serious is this humidity issue? 

Fortunately, not that serious, because most of us live in temperature-controlled environments. Chances are if you’re not comfortable, then neither are your cards.

You’re probably regulating your indoor residential environment so it’s as comfortable as possible for yourself. That in turn means humidity and temperature are already at comfortable levels for your decks. Nevertheless, there are still a few easy measures to observe just to keep your precious decks, especially if they’re collector’s items, in pristine condition.