Hopefully you had a chance to read my previous post about carving a wax model of a ring. In this post, I’ll move forward into spruing the model and casting it in silver.
Once the model has been completed, I attach the ring to a base mold by using a sprue of wax. The details of this process are important because there needs to be a smooth connection and the positioning of the mold should be such that the metal can easily flow upward. The metal will be flowing under extreme heat and very rapidly (within seconds) so if there are cracks or if the mold is angled incorrectly the metal will stop and the casting won’t hold it’s intentional form.
Now it’s time to invest the mold. I need to mix investment with water in an accurate proportion. The investment is sifted into the water and then I mix it with a hand blender. All of this is done while wearing a mask because the investment is hazardous to your lungs. Once the investment is a good consistency I place it on top of a vacuum pump to pull out excess air from the mix. This mix is then poured over the model flask and vacuumed once more.
Once the investment has sat overnight to harden it’s time to put it in an oven to burnout. The oven temperature needs to reach 1350° in order for the wax to completely melt. This is where the lost wax part of the name happens because the wax gets lost/evaporated and the space is left in the mold where the wax originally lived. The flask will need to burn for several hours and then be kept at approximately 900° until we’re ready to throw the silver.
Now let’s move on to the exciting part. The video below will show you what happens more accurately than I can describe but I’ll give it a shot. I put the accurately measured amount of metal into the crucible of the casting machine. I heat the metal it until it turns to a glowing liquid. Then the arm of the casting machine is lifted and the metal will very quickly flow into the flask.
Now I need to take out the flask and make sure there is a button on the end. This was created by the extra metal that filled the mouth of the mold. Once I’m sure it’s there I can move on to quenching and making sure the piece molded properly. Stay tuned for next month’s post for the next part of making a lost wax casting!