In this project I make Thor’s new Stormbreaker Axe, full size from casting resin and aluminium powder. I’m very happy with the end result considering it was my first time doing anything like this.
Stormbreaker Axe head
The first thing you need is a model to make the mould with. I downloaded a 3D print from the internet and printed it myself. Although you can buy them already printed online from places like Etsy, or have them printed for you online. Despite 3D prints are cool to look at they are not strong, so it simply wont do to leave it. I gave the print a smooth coat of grey filler primer then it was time to make a mould.
Making the Stormbreaker mould
If you look at the Stormbreaker axe head it’s a funny shape. We could build a simple box, but that would waste an awful lot of silicone. That is why my wooden box is a funny shape too, it reduces waste. Ideally you want at least 25mm or so of casting silicone around an object for strength. Because the axe head is so large I decided to increase the area around the axe head to make the mould a bit stronger. Essentially I just took an educated guess but it’s somewhere between 40 and 50m. All the casting materials are listed on the page and bought from Easy composites (I’m not affiliated in any way).
The silicone casting rubber I used was CS25 from EasyComposites. In small scale tests it picked out details very well and cast objects nicely without the need for using a vacuum chamber. It also allowed plenty of mixing time and a 24 Hour final cure. Perfect for mixing the product well and not feeling rushed. Easy composites have some good instructional videos on this product, a brilliant technical help phone line as well as PDF’s on how to use it.
The inside of the wooden mould was painted thoroughly with car paint. This is a VERY important stage. CS25 silicone will not cure correctly if moisture gets into it. Wood contains and absorbs moisture even if it feels dry, this is bad. So the paint allows the silicone to cure by keeping the moisture from the wood, out of the silicone rubber. If you use any casting products always read PDF’s first.
The Duct tape used on the mould is to hold it together (with the nails) and to stop small leaks. This also allows me to take the mould apart when needed.
Calculating volumes for casting and mould making
To cast the axe head, we need to know its volume. I did this with the water displacement method. I simply put water into a plastic container and marked the side with a marker pen. I then pushed the Stormbreaker axe head under the water and marked the new height. The difference between the two marks is the volume of the axe head. So if you add a measured amount of water until the top mark is the same, that’s the volume of the axe. In my case that was 4.7 Litres. This is the amount of casting product required to cast the head.
Next it’s time to calculate the internal volume of the wooden mould. This was also a complicated shape. In the end I poured in Kiln dried sand from a hardware shop in 1 litre increments. This worked out to be about 28 litres, close to where I had previously guessed with some head scratching mathematics.
Now all you have to do is deduct the 4.7L axe head from the 28L mould to get the internal volume of the mould. I called it 26L of CS25 silicone to be on the safe side.
Making a silicone mould
After hot glueing the 3d print inside the mould it was screwed and taped shut, then set onto a level surface. I used plenty of hot glue, the last thing you want is the model floating to the surface! I probably should have used Epoxy glue thinking about it.
I mixed the CS25 silicone in two half batches to make the mix(s) easier. This was done with a rectangular piece of wood trying to mix very thoroughly but not create air bubbles inside the mix. Mix it until you know it’s mixed, then mix it some more. The larger bucket you mix in, the easier it is to mix. I used an old beer brewing bucket.
I then poured the CS25 slowly over Stormbreaker to help capture the details and break any bubbles in the mix. Then I did it again for the second mix.
In hindsight I did manage to trap some small bubbles in the overhanging details in places. If I were to try this again I would probably slow down and dip a gloved hand inside to manually bring any trapped air away from the model and to the surface once the level of the silicone was just above those parts.
24 hours later I cut open the silicone and removed the 3d print before putting it back together again. It is very important that the silicone is well aligned. I checked this by shining a torch inside the mould and adjusting it with my hands while it was in place, on a level surface.
For the Stormbreaker axe head itself I decided to use Xencast p6. This is a tough polyurethane casting resin with a pot life of roughly 6 minutes before it cures. Ideal for high strength applications and curing quickly. Which is good if you intend on putting aluminium powder inside it, the fast cure helps to stop the aluminium powder sinking.
I mixed 500g of Part A, with 500g of 250 mesh aluminum well. Then I mixed 500g of Part B and another 500g of aluminum powder in a separate container. I will explain how this worked out for me in millilitres later.
The two separate mixes, part A and part B, were then poured together into a final mixing bowl. Both parts were mixed thoroughly before going into the mould. There is an exothermic reaction so you have to wait until the cure takes place and the heat is on the way down before a new mix can be added. This can be checked with an infrared thermometer and in my case 45 minutes was the safe point.
In my tests at room temperature 500g of part A was 480ml, and 500g of part B was 420ml. Adding 500g of aluminium to Part A and it was 620ml. 500g of aluminium to part B resulted in 600ml.
Why am I telling you this? Because the PDF said not to work with volumes above 1,000 ml (1Litre). And my final mixed volume was 1,220ml. It all worked out well for me though.
Aluminium casting resin
The aluminium powder in the resin makes the final casting looks like real metal once it has been polished with wire wool. The more aluminum you put in the mix, the better it will look and the more strength it may have. It does however make mixing harder the more you add. When I rang the EasyComposites technical help line, they did say anywhere from 50% to 150% fill by weight works. I opted for 100% (1:1 mix) and it was fine to work with as long as you mix some aluminium powder into part A and Part B first before combining the two.
If you look at my final Stormbreaker closely, you can see a couple of separation lines where the aluminium may have started to settle slightly before the cure took place (a slightly darken or lightened band). This can be a peril of working with multiple large mixes, but it may well have been also the fact I am filming at the same time. Filming is not ideal for concentration when working.
When adding the Xencast P6 mix, I did put my gloved hand inside the mould a couple of times to feel underneath any overhanging ledges and bring out trapped air. A lesson learnt from the silicone stage… Obviously don’t let any product touch your skin if you can help it.
Stormbreaker finishing touches
The pickaxe handle was bought locally for £5 and carved with a Dremel then painted with wood stain. You can wipe the heavy bits of stain with a rag, and even lighten the high spots further with some wire wool when fully dry.
The rope used for the vines was a 1 metre length bought for £3 from a local hardware store. I cut it to length, used 5 min Epoxy to glue and twist it into position, then brushed on a light layer of standard 20 min Epoxy glue. This gave it a stronger more vine like feel and let the acrylic paint not sink it. The thinner twine was just thick string glued into place.
The weathering to the aluminium axe head was a mixture of black acrylic paint and water (called a black wash) which was wiped off all the high spots with a rag. This was also done just slightly to the vines.
Finally I sprayed on some satin clear varnish to the axe head to protect the axe head long term, useful when smashing melons and coconuts.
The above project is aimed at adults for education and entertainment purposes only, not to replicate. Anyone doing so takes full responsibility for their own actions.