Like many scientists who lived 300 years ago, Benjamin Franklin worked on lots of different problems in science. But it wasn’t enough for him to just understand the science. With each discovery he made an invention: something to make people’s lives easier and safer. He made no money from his inventions, believing that they should be used freely by everyone.

You will need...

Several wine glasses. You may want to try different shapes to find out which is easiest to use
A jug of water
An audience
Another musical instrument, such as a recorder or piano, to tune your glasses (optional)


How long?

This activity can take as long as you like. You can put together a simple glass harp in five minutes, but you can take much longer if you want to tune the instrument and practise enough to make some music on it.

What to do...

As there is water involved there may be spills, so beware of wet slippery floors. And because this only works with glasses, you may need to take extra care not to break the glasses if the students are taking part themselves.

Full instructions are given on the students' pages.

You can split the students into teams and devise a competition where one team (or yourself) plays a tune and the other team must identify it!  Alternatively ask students to perform in a school assembly.

What is happening?

The wet fingers slide and stick as they go round the glasses. This causes the glass to vibrate, which makes the air inside the glass vibrate. This works in very much the same way as the bow of a violin sliding across and sticking to the strings to make them vibrate, with the wooden violin box amplifying the sound.

The glass armonica

Students can have a look at a glass armonica on the BBC History of the World in 100 objects site:
http://www.bbc.co.uk/ahistoryoftheworld/objects/2HirTsxfT5y1VKp9IyVl2Q

There are many videos available on You Tube of people playing the glass armonica. You can also search for 'glass harp' to see people playing complex pieces of music on singing wine glasses.

Curriculum Links

Science:

Working scientifically

 

Lower Key stage 2  Year 4
Sound

 

Upper key stage 2 Year 5
Properties and changes of material

Literacy:

Reading - Comprehension

Geography:

Human and physical geography

Music:

Develop an understanding of the history of music

 

 

 

 

Scottish Curriculum

Science

 

SCN 1-11a

Forces, electricity and waves - Vibrations and waves

Collaborating in experiments on different ways of producing sound from vibrations, demonstrating how to change the pitch of the sound. [Note: level 1)

 

SCN 2-11a

Forces, electricity and waves - Vibrations and waves

explaining how sound vibrations are carried by waves through air, water and other media.

Expressive arts

EXA 2-17a

Music

Unusual instruments

As well as an interest in science and politics, Benjamin Franklin also loved music. He played the violin, harp and guitar. He lived at a time when many of the world's most famous composers were alive, such as Handel, Bach, Mozart, and Beethoven.

While he was in Britain, Benjamin Franklin heard a concert performed on a glass harp. These were wine glasses filled with different amounts of water. If you rub the rim of the glass a note can be heard.

The Glass Armonica

Benjamin Franklin was inspired by the concert to make a new instrument, the glass armonica. Instead of a row of glasses filled with water he had a glassblower make a series of glass bowls of different sizes. These were stacked on their side and could turn, dipping into a trough of water so they remained wet. The musician simply had to touch each glass bowl as it turned, to make the sound. Both Mozart and Beethoven composed music for the glass armonica!

Glass Armonica

 

Make your own glass armonica

Download a pdf of the instructions here.


You will need...

Several wine glasses. You may want to try different shapes to find out which is easiest to use
A jug of water
An audience

Glass music

What to do...

1. Take three of your glasses and fill them to different depths with water.

2. Wet your finger and rub it gently around the edge of the glass. You may need to hold on to the base to keep the glass steady. Try changing the speed and firmness until you hear a note.

3. Practise with the three glasses until you become good at moving from glass to glass, making a note each time. Notice how you get different notes with different amounts of water.

4. Add more glasses. You can now change the amount of water in your wine glasses, and tune them to match different notes on your other musical instrument.

5. Amaze your audience with your glass harp... and your musical talent!

Does having more water in the wine glass give you a high or a low pitched sound?
Is it possible to make the sound louder and quieter?

What is happening?

Your finger is sliding and sticking as it goes round the glass. This causes the glass to vibrate, which makes the air inside the glass vibrate. The vibrations travel up to your ear through the air, and your ear hears the vibrating air as a sound.

You might be able to feel the vibration in your finger a little as you rub the glass.