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Is there really not an electric kettle that can be controlled in single digit increments and heat to lower temperatures like 85 or 90 degrees F? What am I missing here?

This will teach you how an electric kettle works:

https://www.youtube.com/watch?v=VzqN4Cn8r3U

You have a mechanical switch. If you want something that is more customizable, you need to get a more advanced kettle. Also realize anything kept below 140°F is considered not food safe. I personally use a Zojirushi water heater that's awesome, but it is meant for common tea brewing temps in the hundreds.

I dig old computers and used bookstores. 

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@whatrocks Have you looked into a sous vide? It will do exactly what you want, but is intended to be used for water bathing something else in a sealed bag.