I use this method to heat up my greenhouse in the winter when weather drops really low.  It works and has helped me a lot. Maybe this will help someone in the North or East who has their trees in garages or shed on freezing nights.

Nice idea for those who do not need a ton of heat,
Thanks!

what a great idea for outdoors greenhouse (to protect the plants from freezing)or even camping (to keep the cattle hot). I wonder if just one candle would be enough. The tea candles last 4 each, 100 pack for $5.00 in IKEA

Aaron, my greenhouse is a 10 by  20. I use two candles and it has worked out fine. I usually stock up on holiday clearance candles  or candles at the dollar store. Since I only heat at nights (freezing nights) two candles have lasted me a good 4-5 days(only nights). It keeps the room warm and ice or frost from forming. The Crisco candle method works a lot better and longer.

Rawgreens,
Thanks for posting.
Your Mini Masonry Heater has many applications for providing heat in the colder zones.
I've used a kerosene lamp powered chicken brooder successfully, replacing the candle with any inexpensive kerosene lamp would provide 24 or more hours of continuous heat on a pint of fuel. The inexpensive kerosene lamp at Walmart...Cost $7.00

Lol I was just watching this video the other day on YouTube.

Hey great idea.
Is there any issues with the fumes produced?

 Build this yesterday using 3 clay pots and a candle in a small pail. Brought temp up 15 degrees in a 12x10 hfgh overnight. It was placed beside a 30 gallon plastic water barrel with a brick spacer and it worked.  Going to up grade to the Crisco and/or oil lamp.

 Richard
 Zone 6 MA. with Greenhouse