Rigging Cards With RFID ChipsSocial Things
It is surprisingly difficult to convincingly conceal an RFID chip inside a playing card.
This was a genuine dilemma. Finding the right paper stock was a nightmare as it had to live up to several criteria:
- The paper had to resemble a playing card in thickness, feel and texture.
For this purpose I confiscated a deck of Bicycle cards from Alex (I ended up eviscerating a card with a scalpel to unlock its secrets. That’s how committed I am). Of course Bicycle works with a patented paper stock that has a particularly slick and pleasant texture which can’t be replicated with normal paper. I had to find something preferably coated, ideally gloss but not sticky (so photo paper was out of the question).
- It had to be as opaque as possible
The entire enterprise hinged on convincingly concealing the RFID chips. This was non-negotiable. This means that, say, Heaven 42 – which has the right texture but is a bit too transparent – would be useless. This can usually be solved with thicker weights, except:
- It had to be between 140 and 200 GSM
I would be sticking two sheets of paper togerther to make the cards. anything thicker than 400 gsm total (and that’s already stretching it) and the result would not look or feel like playing cards anymore. The cards had to be convincing, meaning as close in handling and appearance to a real playing card as possible.
Here are some of my prototypes:
These are the original prototypes which I used when setting up the RFID scanner module and to compare the two chip types I had on hand. The larger, round stickers were ever so slightly thinner and had a considerably better range, which is why I ended up going with them. The paper was 140 gsm card stock from the card shop. Pretty but the texture was completely wrong and the tags were so easy to see through the paper at all times that I did not even need to remember which chip was in what card.
This was the 160 gsm version of the default gloss stock that is in the university printers. I was teying to see whether a dark print on the background would affect how easy it was to see the chip. As it turns out, the dark background helped though the paper left a lot to be desired. I could still see the chip (though not quite as well) and the paper felt a bit too cheap and basic to be suitable for playing cards.
This was a disaster. The white paper on top had the right texture but was quite thin. It was around the same time I had the idea that maybe I could use three layers instead of two, adding a thin sheet of black paper in the middle to make sure the chip cannot be seen through the paper. The chip can be seen very clearly through the paper. The white paper on top also turned out to be a giant sticker and I get the impression that the people in reprographics would not thank me for that.
This was the point at which I went to Shepherds in Victoria and spent about an hour looking through their paper. As usual they delivered on having everything but the kind of thing that I was looking for (hint – Shepherds is useless, just use GF Smiths). I got a few bits of reasonably smooth card stock (at an unreasonable price) which turned out to be just the right thickness to comfortably conceal the chips but the texture was terrible.
Infuriatingly, I found the best paper in Scott’s office in Finishing. The one place I forgot to look. In other news, Scott is the best. The amount of times that man saved my behind close to deadlines is uncanny. The paper is a bit thicker that I would have liked and it isn’t quite as smooth and nice as some playing cards though that standard would be impossible to achieve with my resources. It’s a gloss, coated stock, reasonably smooth and the prints are quite decent. You can see the paper bulge a tiny bit where the chip is but only when you are looking for it.
The cards ended up looking very decent in the end. I did not design a full deck because of time constraints and the backs are solid red, as I could not guarantee that the two sheets would align reliably enough for a full back design to be viable.