PERMANENT ADVENT CANDLE

I woke up early this morning, realising that I’d fallen asleep with the bedroom lamp on.

Normally it’s on a timer. It switches itself off at midnight, and then comes on again when it’s time to wake up. Last night though, I turned the timer off so I could keep reading… and then for some reason, the next thing I knew I was waking up at 5am.

“Urgh,” I said. I reached across and flipped it back to timer, plunging the room into sweet darkness.

I had just about enough time to lie back on my pillow, breathe, and blink once… before the timer switched the light back on.

I sighed but it was too late. My eyes were open and there’d be no going back to sleep.

“How tall,” I wondered, staring at the ceiling, “Would my Advent Candle have to be to keep it burning through the whole of Advent?”

I’d lit it yesterday afternoon and worked out that it burns through a ‘day’ in around 30 minutes. If I had lit it at midnight on December 1st and wanted it burn through to Christmas morning without relighting, how much candle would I need?

Well. It turns out that it would need to be over 14m tall, probably about 46 feet. I imagined myself with a step-ladder and a very thin red candle in the garden. It would never work, would it?

According to one website though, paraffin wax has a burn-rate of 7.5 grams per hour and a density of 0.9 grams per cubic centimetre.

What if it were a shorter but much wider candle? Would that work? 

I did some more maths.

H = Number of hours in advent = 1,440

R = Burn rate of paraffin wax (g/h) = 7.5

D = Paraffin wax density (g/ccm) = 0.9

A = Mass of candle required (g) = H x R = 1440 x 7.5 = 10,800g

V = Volume of candle (ccm) = D x A = 0.9 x H x R = 9,720 cubic centimetres

So it would be a candle that weighs 10.8 kg (A). It would be horrendous to lift into position, however tall or wide it ends up.

I have another candle that has a diameter of about 10cm. As it turns out, the flame from that one isn’t hot enough to melt the wax at the edges, so the candle is slowly boring its way through a tube of wax. It’s getting harder and harder to light it without burning my fingers actually, but that’s another story. The point is, there’s obviously a maximum diameter for a candle, such that its melt pool extends beyond its width. Judging from this other candle I’d say the flame has a melt radius of around 4cm, 5 at most.

That gives us a fixed maximum diameter (Y) of around 9cm.

Y = 9cm

V = 9,720 ccm = diameter (Y) x π x length (Z)

V = πYZ = 9,720

Z = 9720/(πY) = 343.8cm

So my permanent Advent Candle would end up being 3.4m tall and 9cm wide. It would weigh the same as a kilo of rice or a car tyre, and it would be perpetually burning for 24 straight days.

At this point, I started wondering whether different types of wick might burn hotter, and whether that could increase the melt radius. But of course, then you’re in a world of complicated chemistry, and to be honest, you can take these things too far.

After all, if I wanted a steadily burning light in my flat for whatever reason, I could always just leave my bedroom lamp on.