I have restarted the test. This time I have planted seeds directly into plant pots. I have planted three tomato seeds per pot, I have used six pots, and this time divided them into three groups - seeds that are being fed water boiled in a microwave oven, seeds being fed water boiled in an electric kettle, and seeds being fed ordinary tap water.
I expect I shall have some photographs in about a week. I planted the seeds on April 12th, and already a couple are breaking through the soil.