Really awesome idea for an experiment, especially for those interested in general candle-based heating.

I did this with home made lard candles and clay pots, it did a great job! 😊

Erica, there a vids on creating mini-heaters using 3- wick candles and assembled clay pots...the clay pots distribute the heat. Would you be interested in trying that in your greenhouse for us viewer's?

This is actually fascinating! Truthfully I hadn’t expected the candle to make a noticeable difference but your video shows that it can - great! It would certainly be a handy way of keeping back the worst of the frost for those times when you think you might get caught out with what you have in the greenhouse. Super video!

I have covered my plants with bubble wrap and fleece on the coldest nights, but it's only cabbages and things like lupins and foxglove seedlings plus salad leaves

Thanks for this info Erica. I really enjoyed this video.

Such a good experiment! We had down to minus 14 one night here in Scotland. Even today I went into the greenhouse and there was ice inside the roof even though the snow has melted the puddles were frozen this morning. I know people put tealights in terracotta pots but tealights dont last. This is a brilliant idea. Thanks Erica.

Love this experiment Erica. I’ve tons of Christmas candles I’m allergic too so this is a perfect way to use them up and get my greenhouse warmed up!

Hi Erica, I'm Dave, Your video is brilliant as all your vids are. Just like to mention that I understand that this is an experiment for a bit of fun but could also be very useful to people like me who for one, has already ordered my 100 hour candles. Reading all the previous comments people are telling you that you must try this and that, they obviously don't realise that you already know these things and that your experiment was just that! An experiment! We have all seen and read about the different ways to heat or keep the frost out of the average greenhouse and I think that your experiment was very informative. The people in the comments that are telling you about tube heaters and whatever must think you are new to the game, I know different, I have been following you for ever and I take on board all your vids which help me so much in my gardening adventure. Thank you Erica for sharing your experiences, Best regards, Dave.

Could use solar to heat and store. Or black barrels of water that holds the heat over the night.

Your thermometer is right next to the candle. So it’s only measuring the “heated air” right there. The heat from the candle won’t emanate much farther than that.

I bet adding stone block or terracotta surrounding the candle, would help it’s heating efficiency as it would warm and distribute heat longer. My south facing front yard has loads of stone work and the stone really holds the suns heat. I can work soil much earlier than anywhere else in my yard in the spring. It’s an interesting microclimate. Fun experiment!

It depends on very many factors.

Hi Erica. Thanks, I loved watching your experiment and was surprised at the results! I'll pass it on to friends. One other way of heating seedlings in a greenhouse is to build a hot bed. I wonder if it also heats the air around it? Also I've used thermal mass in the form of bottles filled with water. The greenhouse can heat up to over 30 on sunny days in winter. We don't get snow here in Auckland NZ, but very occaisionally a frost. When I compared our little greenhouse to a friend's one we had warmer overnight temperatures for our summer seedlings with the bottles than did he, and they grew faster.

nice experiment erica

I love a fun experiment 🔬 hey what else are we going to do in winter 😂😂. Keep warm Erica stay safe 👍👍🇨🇦

You need to have floating wick holders in several small tins using vegetable oil and tissue paper for wicks. If you insulated the greenhouse with say bubble wrap then two floating wick holders would raise the temperature by about a degree C. So ten would raise the temperature by 5 degrees C. This is approximate and depends on the size of the greenhouse. if you have any sensitive plants, the best method is to enclosed them and just heat that enclosed space. If you are able to lay on electricity then use a heat mat under the plants. A 21 W mat will make a massive difference and again enclose the plant/ tray to retain the heat in that space. You could also use a 50W slow cooker or tube heater which are very cost efficient and will produce a lot of heat. A 50W heater will cost around 2p per hour, so 48p per day. The 21W mat will more than halve that. Of course a paraffin heater will produce the most heat and may last about a week for 4 litres, should be at least 4 days (Some small paraffin heaters will last well over a week maybe ten days). Paraffin is more expensive than vegetable oil. Also used vegetable oil is just as effective and if you can get it very cheap. The key is not to try to heat the whole greenhouse but the spaces around your plants and it is only worth doing if you use some kind of insulation to trap the heat. Messing about with 1 candle and no insulation is pointless.

Hi Erica, I love your videos on the hundred hour candle. You should of had to two terra-cotta flower pots which would’ve made more heat. I will try and get video can’t get but look at simplify gardening about seven years ago it dose work

Nice one Erica, love these sort of trials! Could be you were getting a false reading as the thermometer was so close to the candle? A candle typically outputs 100W of which 90 is heat and 10 is light so it is probably as good as a small tubular greenhouse heater. A 100W heater would cost £3.40 to run for your 100-hour trial. Soy wax candles give off more heat than paraffin wax ones and could be better for the environment. And it may be more effective to place the candle on the floor so it heats more of the air before reaching the cold glass.

I really liked this idea a lot. Depending upon which direction the greenhouse is facing the sun will help melt some of the ice at the right temperature. The north side I believe would be the least helped by the sun the south side the most. So the candle 1 or more placed in the right spots would raise the temp and melt snow/ice. I hope you find out a few more things

One thing that you can do in addition to candles is large containers of water near your tender plants. A 4L jug of water placed in the greenhouse during the day will absorb some of the heat produced by the sun and slowly release it overnight. This won't heat the greenhouse but if placed near the plants it will be enough to keep the frost off them.

I've used mass amount of milk bottles filled with rain wate these past couple/few years; good purpose of using excess loading water from 1 butt to another. I've also used different forms of foams (that would otherwise be thrown into landfill) against the outer walls within the greenhouse. And of course, reflective silver bubble wrap. All 3 usages above were free, saved throwing away, and easily installed 😂. I've sure if you had put that candle in the middle of some bricks with an upturned terracotta plant pot, the candle would have generated more heat ❤

I have heard about keeping chickens in green houses for warmth too! Lol

I don't have a greenhouse, but I've watched videos of people who use the candle and put it under a terra cotta pot. The pot absorbs and radiates the heat. One guy put a big pot over the candle and then put a little smaller pot on top of that one and yet another on top of that one. It looked like a big inverted cone. He also puts wicks in a tub of crisco, which burns a long time.

I use candles and pillar candles are the best and mine are on tiles and it increases the temperature by 2 degrees.

My friend had a greenhouse in northern Minnesota (temperatures get down to well below freezing for many months). He has a lot of big black pipes that absorb heat during the day and radiate heat at night. In the summer months, he drains the water out of the pipes. The black plastic pipes are the bigger plumbing pipes with the bottom cap glued on (to make it leakproof) and I believe the top cap comes off to drain it - but I’m not sure. He kept plants in there all winter and that was the only heat. Now, I live in a much more moderate climate so we only have a few days of freezing temperatures and the gardeners post pictures of water jugs painted black and set around their plants under row covers. Black stones or dark bricks help too.

I just try magical thinking currently (wing and a prayer 😄) but maybe I should sort some heating options out.

This was such a great experiment. Someone else beat me to posting that terracotta might work better.

Hi Erica just Subscribed great video was just wondering would it give of more heat if you put it under a terracotta pot

The candle is supposed to be placed on the floor with a large clay pot (one with a hole in the bottom) placed over the top. The clay pot will be warmed and help radiate that heat into the greenhouse. Additionally, it is safer to keep the candle covered.

Thermal mass heating is free. Use barrels filed with water and place them inside the greenhouse. The water will heat up by the sun during the day and release the heat back in the greenhouse during the night.

It got to minus 5 Celsius here in Herts, our pipes froze. Which is unusually cold for us.

Well I’m surprised at the difference it did make… as it was heating it fairly well I believe from watching it. I only have a plastic covered greenhouse and the same in a shelving unit but I do find it makes a difference. A huge difference at time. And a candle may help but atm I am not doing anything but onions so they are ok

Aside from gas and electricity would be water and heat but I guess that doesn't work so well in your temperature. The coldest it gets out here in North Carolina i'd say would be 17 but usually it hangs around 20° At night for a few nights in a row.

Put the candle under terracotta pot ,stack a few sizes .

An interesting experiment. I think it would work with two candles or in a smaller lean to type greenhouse ? we have had exceptionally cold temperatures though. I'm going to give this a go.

Very interesting results , as mentioned a clay pot over the candle will help as would more candles and some bubble wrap insulation layer. Also concrete floors or stone chippings are great for thermal mass heating since it traps heat during day and releases it at night. Barrels of water will do the same thing . Great video thanks.

where to buy or how to make those candles

When you say up here? Are you in the North of the UK?

Use buckets or barrels of water

There are greenhouse heaters that use Paraffin and work well

Make a sand battery.

It heats up the air but most of the heat (and light) it produces passes directly out through the glass. A thick tarpaulin draped as much as possible over the greenhouse would prevent this heat loss. Generally if light can't get out, heat (infra red light) can't get out either. People who go camping in cold weather don't seem to understand this simple concept!

Erica. You are one talented girl. Where did you get your 100 hour candle.

A clay pot heater or two would have done the trick much more efficiently. Place them in the path of your greenhouse down low to maximize the heating effect.

How to keep your greenhouse warm in winter. Goes into the snow covered greenhouse, starts talking. All the while leaving the door open. Right.

Heat rises. Put it on the floor.

5:12 actually that's -0.1°C not -1°C.

Iff there's no air in there then the candle will go out

It is lame to use Celsius. The number 23 by numbers standard is not high, it is quite low. I don't understand why anyone would want to use Celsius as their standard? Oh well.

that space needs 6 candles and done everything will be perfect if you add 45gal water drums x 5 then it will retain and then block insulation on north side and 12 candles a week cheap safe and grow food very simple.