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Anyone who's collected Magic for a while knows the unfortunate tendency for foils — especially older foils and the heavier promotional foils — to curl up towards the foil side (presumably as the cardstock expands from moisture). Unfortunately, this not only makes it harder to use the foils in decks (they become clearly marked — not a serious problem but still an annoyance for formats like Commander, and a more substantial problem for someone hoping to put e.g. some old foil Rancors into a Standard deck), but it presumably also decreases their value notably.

Unfortunately, just sandwiching the foils in between regular cards doesn't work very well — there isn't generally enough pressure from the regular cards to keep the foils flat; worse, this scheme doesn't really allow for storing a number of foils together (where they'll all curl together). Does anyone have any good suggestions for how to straighten out curled foil cards, or to keep foils from curling in the first place?

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  • I have found that older foils curl less
    – Neil Meyer
    Aug 3 at 17:37
7

Sleeving cards helps keep them flat. Additionally, there are "perfect" or "pro" fit sleeves, which fit cards tightly and can be inserted inside other sleeves. The stiffness of double-sleeving will help a card maintain its shape, as well as protecting expensive cards from rough shuffling or when they are migrating between sleeves.

This, in combination with a deckbox that compresses the cards a little (most of the ultra pro plastic boxes will fit 75 double-sleeved cards, just about) will keep your foils from bending too much. In general, the best advice is to keep them in a deck and keep that deck packed tightly.

4

My understanding is that the tendency for foils to curl is due to humidity. The difference in moisture absorption between the foil side and back of the card causes the card to curl.

With the caveat that I've not tried this myself, I suggest adding silica gel or a similar desiccant to your storage box.

As far as storing foils together, you might try flipping each card so the foil sides and back sides touch.

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  • 1
    My experience living in an extremely dry climate has been the opposite, card warping here is far worse than I ever saw before moving!
    – Affe
    Jun 28 '13 at 5:24
  • im guessing the closer your climate is to the climate where the cards were originally printed, the less they will warp
    – Patters
    Jul 1 '13 at 9:13
  • @Affe Which way do your foils curl? From the front of the card, is it convex or concave? My guess would be that foils warp concave in humid climates (as the paper back absorbs moisture) and convex in dry climates (as the paper back loses moisture).
    – Peeja
    Aug 31 '14 at 16:31
2
+250

Curled foils are caused by humidity. You can undo the curling of a card by keeping it at approximately 72% humidity for a couple of days.

A great way to do this is to buy a two-way humidity packet rated at approximately 72% humidity - these are typically advertised for use with cigars. After using one of these packets in a plastic bag with your curled cards for a couple of days, it will flatten, but will curl again if later stored at a different humidity.

This article from MTGGoldfish describes the experimental process that produced the 72% humidity number. The article also recommends double sleeving and storing cards at approximately 60–65% humidity in a low-circulation environment to prevent them from curling again in the long term.

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As far as the silica gel idea, I believe it does help quite a bit, as I to was wondering why my foil Archon of Triumvirate bent far worse than my foil Hypersonic Dragon(about 4 months older than my newly opened Archon) which i keep in my desk drawer. Upon getting a new laptop earlier in the year, I threw the silica gel that came with the packaging into my desk drawer and my foils stored in the drawer showed a significant difference to newer foils i obtained and did not store within the same drawer. Even today a foil i got less than a week ago reached the same condition of Archon when kept outside of said drawer and my hypersonic is still holding up pretty well unsleeved while in the drawer.

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Some cards came out of the box curled. The From the Vault series was notorious for this. You can double sleeve the cards, but unless you double sleeve fresh from pack and never unsleeve. It is not gonna help. Dragon Shields are the only real sleeves I have found that help with this, but even then when the curling is from poor card stock then nothing on Gaes green earth could stop the curling.

It is hard to say exactly what is poor card stock and what is poor handling. I have a set of foil Shadowmoor kitchen finks that have never seen sleeves and have no curls. It depends heavily on the era and which MTG printer services you area. I think Europe and South Africa falls under Carte Mundi jurisdiction and I really have had no long term problem with card quality, although I must admit it does seem like Ixalan era there was a worldwide problem with card quality. I'm not exactly sure how independent printers in different parts of the world all lowered there printing quality in unison.

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There is a very good article on mtggoldfish. To summarize the points relevant to this question:

As asserted in the question, curling or cupping of foils is a result of improper humidity. To be more specific, curling (or arching) happens when the humidity is too low, cupping happens when the humidity is too high.

To keep foils flat, you need to keep them at the proper humidity. The ideal humidity for most foils is somewhere around 60%. This can be achieved with humidity regulator packs. The article recommends 62%, likely because this is an easily available target number for humidity regulator packs (though this may be slightly too high for older foils). The ideal humidity is not constant for all sets though; Commander Legends for example is probably somewhere closer to 65%. Finally, double sleeving foils helps them retain their shape likely by helping prevent changes in humidity.

To fix cards that have already curled or cupped, use humidity outside of the 60% range for a short stint. Using high humidity for a few days can fix foils that have curled, and using low humidity for a few days can fix foils that have cupped.


Credit to @Toroid for finding a really good link. I am posting a separate answer because I believe @Toroid's answer missed a number of key aspects of the article, especially in relation to this question.

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  • @doppelgreener The question is asking how to keep foils flat and how to straighten foils that are bent. I summarized the parts of the article that answer both parts of the question. What aspect of the question am I missing? As to why I posted my own answer, Toroid focused exclusively on how to flatten bent foils, when the main part of the question (and thus my answer) is about how to keep them flat. I believe my answer is sufficiently different to be far beyond the scope of an edit.
    – Zags
    Aug 3 at 14:08
  • @doppelgreener Also, none of my answer is a quote of the article. This is entirely my own summary and synthesis.
    – Zags
    Aug 3 at 14:10
  • @Zags Thanks for your supplemental information! I've edited my answer to include more concrete humidity numbers for long term storage. Was there any other aspect you think I missed with my answer? I'm happy to edit my answer some more to include anything else 😁
    – Kyle Pollard
    Aug 3 at 17:18
  • This is not entirely true, from the Vualt series universally came out of the box curled no matter what the atmospheric conditions were. The issue more to do with the quality of the foil treatment, but yes how foils are treated also makes a difference
    – Neil Meyer
    Aug 3 at 17:35
  • @Zags Oh, my mistake! Thank you. Aug 3 at 20:48
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To straighten out cards I would suggest you dry them in an oven. Test with one or two first. Set the oven to 60°C and leave for 30 mins, you may see them curl the other way! After cooling place directly into a sleeve. The theory behind curling is water absorption into the card itself causing expansion thus drying it should to a degree reverse the process. Using a desiccant over a longer period, weeks, should have the same effect. The water should not interact with the card itself over short periods of time but could over longer periods causing a potential change the in the cards molecular structure, since they are cellulose base they are naturally hydrophilic and water hydrogen bonds to the structure. Note that all plastic sleeves will allow the diffusion of moisture through the faces but clearly an open end will be worse. so double sleeveing is a good idea but you could still see curling

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