Activity: Candle Math

To fully appreciate the importance of the value of light, try out some candle math and see how much effort goes into lighting up your life!

We often like to romanticize the past and frequently imagine the soft glow of candles or imagine the quaint candleholder lighting someone’s way to bed. But candle making was hard work!

Various records and diaries from the 1700s give us a clue as to how much effort went into candle making.  In 1728 the New England Weekly Journal described that an average household of nine people consumed about three candles a night. In 1743 Reverend Holyoke, president of Harvard College, described making seventy-eight pounds of candles in just two days—that was enough to last just six months. In the 1790s, Martha Ballard, a midwife, wrote in her diary about making 10-20 dozen candles every few months. She was frequently paid for her services in candles too.

There are two different ways to measure how much light we can get from a light source.  Lumens are how much light an object produces, and lux is a unit of the illumination for an area. 1 lux is equal to about 1 lumen per square meter.

• 10-inch wax candle = 13 lumens; lasts about 2 hours
• 100-watt filament light bulb = 1200 lumens; lasts about 1,000 hours
• 18-watt compact fluorescent bulb = 1290 lumens; lasts about 10,000 hours

Questions for Discussion

• How many 10-inch candles would you need to equal one 100-watt bulb?
• How many 10-inch candles would you need to equal one 18-watt fluorescent bulb?
• How many candles would you need to light your classroom or bedroom based on the lumens you currently use?
• Consult the object story on the short history of lighting. Consider how much time it might take to make all the candles you need using the candle mold.  Or, think about how many rush lights it would take to create the same effect.