From PackRat Recipe Wiki

Foil cards are identical to normal cards except they have images in the border of the card that relate to the family of that card. They are extremely rare, so it is best that you hang on to them.

Foil cards can be found in the markets, on bonus draw cards and even on cards made by a recipe. You won't know it is a foil until you get the pop up congratulating you on your purchase or made recipe. The one exception to this is a foil card that has ended up in the rats or is in another person's pack. These cards you will be able to tell are foil before you pick them up.

Vaulting a foil will give you a point value bonus equal to 200% of the face value of the card.

File:Card Vault-foil-family.jpg NOTE: If you're lucky enough to find/buy a foil, do not do not do NOT use it in a recipe!! The resulting card will have the same chances as every other card of becoming a foil (ie, super rare), and so it is -almost- guaranteed to lose its foilyness!!

[edit] Foil Feat

If you vault one foil from each of the 8 families (see examples below) you will earn a feat of wonder.

[edit] Foil Backgrounds & Examples

[edit] Banana

File:Foil-Banana lg.gif File:Foil-ex-banana lg.gif

[edit] Blueberry

File:Foil-blueberry lg.gif File:Foil-ex-blueberry lg.gif

[edit] Cherry

File:Foil-cherry lg.gif File:Foil-ex-cherry lg.gif

[edit] Chocolate

File:Foil-chocolate lg.gif File:Foil-ex-chocolate lg.gif

[edit] Cotton Candy

File:Foil-cotton-candy lg.gif File:Foil-ex-cotton-candy lg.gif

[edit] Lavender

File:Foil-lavender lg.gif File:Foil-ex-lavender lg.gif

[edit] Lime

File:Foil-lime lg.gif File:Foil-ex-lime lg.gif

[edit] Mandarin

File:Foil-mandarin lg.gif File:Foil-ex-mandarin lg.gif