Somewhat Realistic Light Sources

Hello. It’s been a while. I blame my uni workload again, it’s been pretty heavy.

Anyways, I started thinking about light sources the other day, and attempted to research some things.

Duration

How long does a light last? Well, that depends…

Torches

A normal wooden torch lasts probably 30-60 minutes. Roll 1d4+2 turns if you want to be fancy, or just say one hour if you want to be generous.

Candles

This depends a lot on what kind of material the candle is made of. Far as I can tell, a beeswax candle (expensive) will burn around 5 grams of wax per hour of use, while a tallow candle (the regular kind) burns maybe 10 grams of tallow per hour instead. Tallow candles are also quite smelly and smokey. If you use a thicker wick, it might burn faster.

Oil

Making an olive oil lamp is quite easy, just a bowl with a wick in. From what I’ve read, both olive oil and kerosene (“coal oil” in premodern times) burns around 15 ml/hour on a normal wick. The wick is consumed at such a slow rate it’s basically negligeble. I think someone said they had burnt 1 cm of wick in 150 hours.

Light Amount

This was so stupidly difficult to find proper sources on that I just experimented myself. I made myself a small olive oil lamp, and brought a proper ~75 gram candle. I didn’t make a torch at this time, because that’s a bit of work and requires some good wood (preferrably töre) and or pitch/resin.

oil_lamp
There’s just a small metal cup with some random string as a wick, and some olive oil.

Outside

I first tested them in during the night, outside. It was moonlit, if fairly overcast. As it wasn’t midwinter, I could still make out some things. The oil lantern cast light that was discernable from the moonlight up to around 0.4 to 0.6 meters from the lamp. The modern candle cast discernable light somewhat further, around 0.6 to 0.8 meters.

lamp_vs_candle
Left is oil lamp, right is candle. The middle blob is a tealight.

This means the modern candle cast light maybe 40% further than my tiny, improvised oil lamp. From what I read, modern candles are a lot better than medieval tallow candles, so an oil lamp might still be better than one of those.

Inside

 

I then proceeded test the candle in a the cellar, with windows blocked. The candle lit up a wall approximately 5 meters away. I estimate the light might have been discernable around 8-10 meters from the candle itself. You could read within 1 meter of the candleflame, perhaps 1.5 meters if you have good eyes.

Cost

This wasn’t the easiest ever but…

According to this (pretty useful source, btw) a tallow candle was 1.5 penny per pound in the 15th century, while a beeswax candle was 6.5 pennies per pound.

Through some stupid shenanigans with multiple sources on olive oil in rome and recalculations between currencies, I landed on olive oil being worth around 2 pennies per liter. I have no idea on how reasonable that is. It seems a basic laborer could get half a liter of oil for one day’s pay.

Torches probably cost fairly little. You can make one yourself from wood.

The Results (and/or TL;DR)

Light Source Duration Light Notes Weight Cost
Torch 1 hour 9 m 1 kg 0.1 p
Clay Lamp 10 hours 9 m Uses 150 ml of oil ½ kg 1 p
Iron Lantern 20 hours 9 m Uses 300 ml of oil 1 kg 4 p
Iron Lantern * 9 m Uses a medium candle 1 kg 4 p
Candle, Huge 40 hours 9 m (400 g) ½ kg 1.2 p
Candle, Large 20 hours 9 m (200 g) ½ kg 0.6 p
Candle, Small 10 hours 9 m (100 g) 0.3 p

All the basic light sources provide around 1.5 meters of bright light and 7.5 additional meters of dim light (for a total of around 9 meters).

  • Light: one-sixth of the light radius is bright light; the rest is dim light.
  • Weight: Lamps and lanterns are noted with their weight including its oil or candle.
  • The cost of lamps and lanterns does not include any oil or candles.
  • The default oil is vegetable, and the default candle is tallow. Modify burn time and price as noted.
Material Burn Speed Light Notes Cost
Vegetable Oil 15 ml/hour ×1.0 Stops burning if spilled. 2 p/L
Coal Oil 15 ml/hour ×1.33 Keeps burning if spilled. 4 p/L
Tallow 10 g/hour ×1.0 Smelly and quite smokey. 3 p/kg
Beeswax 5 g/hour ×1.33 12 p/kg

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