Introduction: Welding With Chocolate
This is part of a series of Instructables detailing free science kits and activities developed by the spectrUM Discovery Area in Missoula, MT. The kits and activities are for use at home, in the classroom, or in a distance learning setting with teachers.
For more on how our museum shares these activities with students and teachers, see this video on YouTube.
Explore welding and engineering design with this simple, delicious activity! We were inspired to explore this using a guide from The Welding Institute - check out their website and fantastic video on how they do this. We've worked on a small-scale, kit version of this that is easy to do at home or with a classroom full of students, and incorporates a 3D printed jig.
Students will weld together pieces of chocolate or Andes Mints with hot water in a jar to create I-beams or box welds, then test their strength. Of course once you are done welding, the ultimate test is how delicious the chocolate is!
While there are many different types of welding processes, the chocolate welding process uses a fusion welding technique which involves a localized melting of the material and then bonding the two surfaces together and stabilizing it until the material has cooled enough to provide a secured bond between them. This is really the same with both chocolate and metal. Fusion welding can be performed using gas, electricity or any other type of source that creates heat. It differs from other welding processes because it only uses the parent material and heat to create the bond between two objects. In other types of welding such as arc welding, welding rods or welding wire is added to the heating process in the presence of an inert gas in order to bond the two materials together.
- Chocolate - small Hershey's bars (like the ones you give out for Halloween) work okay. A teacher we work with had the best success with Andes Mints, though - they are dimensionally uniform, melt pretty good, and the individual wrapping is handy. They can be purchased at most grocery stores in the US or on Amazon in bulk.
- A plate, paper is best but plastic or ceramic is okay, just use care and common sense if testing with weights
- Wax paper
- A jig for the box welds - we designed and printed a few versions which we'll share, you can cut up a plastic food container as well
- Hot water - a small glass jar is ideal for this, a kettle or microwave or stove to heat the water is necessary
- A fridge, freezer, or patience
- Heavy things like weights, books, or alternatively a woodworking clamp
- If you want to see how much weight your welded piece will hold, you'll need a scale - a bathroom scale is okay, but a postage scale or kitchen scale is ideal. Something that measures up to about 20 or 30 pounds is fantastic.
Step 1: Create a Jig in Advance
It's helpful to create a jig for your welding in advance. Jigs are used in all sorts of fabrication, from woodworking to welding to paper folding. Simply put, a jig is just something that holds your pieces in place in a specific orientation for a specific process or multiple processes. Ours will hold two pieces of chocolate together at a 90-degree angle while they are cooling.
We designed and 3D printed these mini ChocoJigs to accompany this activity as a kit for students in schools. They print very quickly - I print in batches of 8 and that only takes about 35 minutes at 0.38mm layer height in PLA. You could likely get several hundred out of a single standard roll of filament. They come into contact with the chocolate for only a brief time, and are really intended to be disposable so they don't get gross. PLA is relatively benign and a good choice for this (don't use ABS or TPU). If you are concerned about using food-grade certified filament for this for this, there is information out there on that. If you'd like to use larger planks of chocolate like pieces from a full size Hershey's bar, download the full size one to print instead of the mini. Scale and experiment with what works best for you.
You don't need a 3D printer to make a jig. As indicated in the video in the introduction from The Welding Institute, cutting up a plastic food container works well. You can also just put a strip of wax paper down on a flat surface, and weld two pieces together at a right angle to each other with one flat and the other pointing straight up - just be careful not to knock them over while the chocolate is still melted.
Step 2: Heat Up Water and Prepare Materials
Once you've created a jig, it's time to get welding! With metals, welding is usually done with a torch that gets to a very high temperature using additional gasses like argon, or through the high temperatures created by high current electricity arcing across two metals. We won't be using any of those dangerous things here! To make our welds, all you need is a small jar of hot water. It is helpful to have a jar like the one shown with straight sides, but that is certainly not necessary - a mason/ball jar, old jam jar, wine bottle, etc. is fine. Make sure it is glass and not plastic.
USE CAUTION WHEN HEATING WATER!! It doesn't need to be boiling hot, just about as hot as a cup of coffee or tea. If you are microwaving the water, DO NOT LEAVE THE LID ON THE CONTAINER or it can explode! If you are using a kettle or stove, get the water to just hot enough that it's uncomfortable to leave your finger in but not so hot that it is boiling. I would recommend that if the water comes to a boil to leave it sit for 10-15 minutes before pouring into the jar. For a microwave, use whatever settings are best to heat up a cup of water for tea - usually 2 minutes on high, depending on the size of your mug. Remember, we don't need the water to be super hot here - chocolate melts at a pretty low temperature.
While your water is heating, get out a plate - paper is fine but ceramic is good too, use whatever you have. Set your jig on the plate. If you have wax paper, that is fantastic - it helps a lot with cleanup and for testing the welds, as you'll see in the next steps.
Step 3: Make Your First Welds and Cool
Now it's time to get to welding! I recommend washing your hands before starting this step - always a good idea these days, but especially when handling food that you want to eventually eat. If you are doing this with a classroom of students this is especially important. If you have wax paper on hand, it helps immensely to wrap the jar with a sleeve of it and tape in place - this just makes cleanup of the jar much, much easier - chocolate is pretty fatty and greasy and hard to clean off the sides without a lot of soap.
To Create a Box Section:
You'll need 4 separate pieces of chocolate/mints to create what's called a "box section" (called that because, well, it looks like a box!). Take 1 piece of chocolate or an Andes Mint (or 2 at a time if you're feeling brave) and push the long edge against the side of the jar. Let it melt a bit until you get a good bead of chocolate, but don't leave it for so long that your piece starts to get too small. Start slow at first to make sure you don't melt it too much. Take your 2nd piece and do the same. Then, lay them so that the melted edges are touching each other in the jig. Create another set like this, so that you have filled up the jig as shown above. Once you've created this weld, you'll need to let it cool - it helps to stick it in the fridge or freezer for a few minutes. If it's cold outside, you can set it out there, or just wait for about 5 minutes at room temperature.
To Create an I-Beam:
As an alternative to the box section, you can create an I-beam (called that because, well, it looks like the capital letter "I"). You just need three pieces of chocolate/mints for this. Melt the long edge of one piece as shown above against the side of the hot jar. Set it down on the face of another piece and hold it in place, so it looks like an upside-down "T". Blow on it for just a bit until it will stand up on its own, then stick it in the freezer or fridge for a few minutes. You can also set it outside in the cold, or wait about 5 minutes at room temperature.
Step 4: Create Your Second Welds and Cool
To finish your box section or I-beam, take your assembly out of the fridge/freezer follow the steps above again. Fro the box section, melt the exposed long edges of the two right-angled pieces and assemble them together to form a box as shown above, then set them in the jig in one of the slots and freeze/refrigerate again. For the I-beam, melt the other edge of the piece you melted in the previous step, place on the face of the other piece of chocolate to form an "I", then place in the fridge/freezer again.
Step 5: Test and Eat!
Once your welded piece has cooled completely, it's time to test out how much weight it will hold! Welders and engineers can test how strong their welds are by seeing how much weight they can bear. This is called a stress test or load test.
I like to use a kitchen scale and woodworking clamp, but something heavy like the weights shown or some clean bricks/blocks, etc. will work. Use wax paper here so that whatever you are using to test the chocolate weld does not come in direct contact with it - it allows you to eat a clean piece of chocolate, and to keep whatever you are using to test chocolate smudge-free.
Turn on your scale if you're trying to measure this and tare it with the chocolate piece on there. If you're using a clamp, add the clamp and start squeezing slowly and keep an eye on the weight measurement. Squeeze incrementally until the piece breaks. How much weight did it hold? If you're using weights, stack them on top of the piece until it breaks. How much weight could it bear?
We've found that these small welds can hold up to 20-25 pounds when built very well. If you're using full size chocolate bars, it helps to straddle the weld over a span like a bridge so that it snaps in the middle, and those can hold much more weight.
Once you have tested your chocolate weld's strength, it is time to test how delicious it is! Eating the chocolate makes cleanup much easier.
Step 6: Explain, Expand and Evaluate
Here's a video from one of spectrUM's role models about how she uses welding to create amazing sculptures in addition to her work as a fabricator. Check it out to see welding in action!
Have your students share how their welded pieces performed with the class. Here are a few questions to ask:
- Why are welded pieces of metal so strong?
- Both the box weld and I-beam will hold more weight as a bridge over a gap than just a single flat piece of chocolate. Why is that?
- What other candies or food items might we add to our design to make it stronger?
- Are there other shapes that we could weld our flat stock (chocolate pieces) into that would be structurally sound?
Here are some questions to ask during reflection:
- What would you change about your welded structure if you were to do it again?
- Would you consider a career in welding or fabrication? Why or why not?
- How might you demonstrate arc welding with food products like we did with fusion welding?
- What design could you weld with these materials that could hold more weight - like the weight of a grown adult standing on it?