Asking this because I recently moved to a tropical country and have noticed that my new house has a big humidity problem. The main rooms fluctuate between 50% and 60% but my room will get as high as 80%.
I’m worried that my few PSA graded cards may get damaged overtime due to this extreme humidity despite being in a hard plastic case. I know for a fact that Psa labels can get wrinkly after a while for whatever reason
Get a dehumidifier put the PSA cards in a closet or small area with said device and run the device. Remember to empty the dehumidifier. When I was in Djibouti I used them.
I have no experience with cards curling up in my slabs as Belgium is exactly known for its tropical climate, but it seems highly likely that cards could curl due to humidity.
You could combine that with getting a nice sized pelican case so its air tight too. In the event its not the silica packs would take up the slack. I keep all my valuable MTG and Pokemon cards in a pelican case.
When I lived and worked in Vietnam (often 100% humidity, and a 6 month rainy season…plus I was right on the south China sea shore) my PSA cards appeared to be unaffected. Now they were never there for more than a year before I sent them back to the states.
Take that with a grain of salt. There’s several here that should know way better than me.
I live in El Salvador where humidity is usually above 80% all day every day except on the rainy season where it hits 100% for a couple of months, all my PSA/Becket cards are still as straight as the day I bought them, as for your other cards if they’re not double sleeved I HIGHLY recommend you purchase a box of those silica gel packets and randomly throw them with your cards, they will do the job.
So short answer: No, they won’t curl even in the most shitty of humidity levels.