Force-ripening Green Tomatoes

When I overheard a co-worker saying you can force green tomatoes off the vine to ripen in the sun, I thought this would be a cool experiment to try with the kids. We found our sunniest window, a south-facing one, lined the sill with paper towel and patiently waited. To our pleasant surprise, after just a few days, the tomatoes started turning red.

I did a little research on this and turns out heat is the main proponent required to ripen green tomatoes, not sunlight. This blogger mentioned sunlight inviting rot and toughening the skin. The rotting on my tomatoes was more of a sunburn at the very top, which I always slice off anyway. Further, the texture of the skin seems normal. However, next time, I am encouraged to try his brown paper bag and banana method.

How do you force-ripen tomatoes?