Rinse your cast iron kettle clean with warm water. If there are any stubborn rust stains remaining, you can spray them with oven cleaner, wrap the entire kettle in a heavy-duty plastic garbage bag, seal the end off with tape and let sit overnight. Wash the kettle clean with warm water.
Binary numbers and arithmetic let you represent any amount you want using just two digits: 0 and 1. Here are some examples: Decimal 1 is binary 0001. Decimal 3 is binary 0011. Decimal 6 is binary 0110. Decimal 9 is binary 1001. Each digit 1 in a binary number represents a power of two, and each 0 represents zero: 0001 is 2 to the zero power, or 1. 0010 is 2 to the 1st power, or 2. 0100 is 2 to the 2nd power, or 4. 1000 is 2 to the 3rd power, or 8.
As an example of a binary representation, consider the decimal base number 13. It is equivalent to 2^3+2^2+2^0 and so has the binary designation 1101 with the 1 designating an existing power of two and 0 if it does not exist. Likewise twelve is expressed as 1100 since the number equals 2^3+2^2 and no other powers of two. To double a binary number one needs to only add a zero at the right.