Effect:
This is a classic oil and water effect, where four red cards and four black cards are interlaced, then shaken and shown to show that they have separated back to four red and four black. This is repeated three or four times. The for a climax, the shuffled deck is picked up and shaken. Then it is spread to show that all of the cards have separated into red and black. There are many methods published, I don’t remember where I found these, but you can find a list at the conjuring archive1
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