Thanks to the Welding Institute you can get hands-on and learn about engineering and welding with the most delicious of materials… chocolate! Watch the video and follow the instructions to have a go yourselves at home. If you give it a try we’d love to see your results #VICTAScienceFair.

Welding with Chocolate Equipment

1. Chocolate
   • Minimum four bars but extra may be needed in case of breakage
   • White chocolate works best as it melts quicker, but feel free to try different chocolates to test for different strengths!
2. Heat Source
   • Empty wine or milk bottle filled with hot water
3. Weights
   • Food cans/tins are a good option if actual weights are unavailable
4. 2x Plastic Cups

 

Experiment 1

Welding with Chocolate Process: Welding your Box Girder Bridge

Step 1: Have two bars of chocolate ready.

Step 2: Hold the edges of your chocolate bars against the bottle of hot water until they melt slightly.

Step 3: Press the two melted edges together in a right angle, and leave it to cool – this is half of the box section.

Step 4: Repeat this step again to produce both parts of the box girder bridge.

Step 5: Once both parts are cooled, melt the edges of both halves and join together to form your box girder bridge and leave to cool for 20 minutes.

Hint: it should look like a square tower structure!

 

Experiment 2

Mechanical testing of a bar of chocolate verses the box girder bridge made from welding with chocolate.

Let’s try testing different chocolate bridge.

Firstly, we have a single chocolate bar, this is called plank bridge design.

Step 1: Place a single chocolate bar on top of two objects. The edge of the chocolate bar needs to be in the centre of each object. These two objects can be two empty glasses or mugs of the same height, flipped over.

Step 2: Gradually begin adding weights to the centre of the bridge.

Observations:

• How much load have you added when the bridge breaks?
• Does another chocolate bar break at the same load?

 

Let’s try testing the box girder bridge you made!

Box Girder Bridge

Once your box girder has completely cooled and solidified along the edges, it’s time to test its strength.

Step 1: Place a single chocolate bar on top of two objects. The edge of the chocolate bar needs to be in the centre of each object. These two objects can be two empty glasses or mugs of the same height, flipped over.

Step 2: Gradually begin adding weights to the centre of the bridge.

Observations:

• How much load have you added when the bridge breaks?
• Does another chocolate bar break at the same load?

 

1. Non-Destructive Visual Test

Weld defects: feel the edges of your box girder. Is your box girder melted and joined perfectly along each edge? Can you feel or see any weld defects or distortions (HINT: distortion means the beam is not a perfect square in section)?

A question for you to think about: Will any of these inspection or visual findings affect the strength of the box girder bridge?

 

2. Destructive Testing

Repeat the first test using your constructed box girder bridge, gradually adding weights.

 

Some questions for you:

If the box girder bridge is made of 4 bars, will the bridge be 4 times stronger than the single bar bridge?

How much more load can you add to your box girder bridge compared to the plank bridge?

Did your bridge break? Were the welds the weak points of the bridges that broke?

How much stronger would your box girder bridge be if all the welds and joints were perfect quality?

 

Send your results to sciencefair@victa.org.uk, we’d love to see how you get on!

You can also download the resources in pdf format here:

Download the ‘Welding with Chocolate – Student Factsheets 2021’ pdf

Download the ‘Welding with Chocolate – Teacher’s Factsheets 2021’ pdf