This video presents a detailed, DIY guide to melting various metals, including aluminum, brass, copper, and even cast iron, using a household microwave. The core components required are a silicon carbide crucible, which absorbs microwave energy and converts it into heat, and a homemade insulating chamber constructed from ceramic fiber blanket. The creator provides step-by-step instructions for building the chamber, outlining methods for smoothing surfaces, drying with a microwave, and optionally hardening the ceramic fiber with a blow torch or boric acid solution. Two techniques for crafting silicon carbide crucibles are demonstrated: one using a glass mold and another utilizing 3D-printed molds with sodium silicate as a binder. The video also covers critical aspects such as preventing crucible sticking with kiln wash, optimizing melting efficiency through proper material selection, and practical safety considerations for operating a microwave in this unconventional manner, including the importance of personal protective equipment and understanding factors that affect melting times.
Summarizing Microwave Metal Melting
0:00 Introduction to Microwave Metal Melting: The video demonstrates a method for melting metals like brass, aluminum, copper, and cast iron using a standard microwave, showcasing brass scissors as an example.
1:18 Essential Equipment: The core setup requires an ordinary microwave (often used on its side), a silicon carbide crucible (which absorbs microwaves to generate heat), and an insulating chamber made from ceramic fiber blanket (Kaowool).
1:58 How It Works: Silicon carbide efficiently absorbs microwaves, converting them into heat. The ceramic fiber chamber then insulates the crucible, trapping this heat to reach temperatures sufficient for melting various metals.
2:18 Building the Insulating Chamber: Instructions cover rolling strips of ceramic fiber blanket around a cylinder, securing the layers with Kapton tape (rated for high temperatures), and cutting to size. A respirator is essential when working with ceramic fiber.
6:00 Smoothing Surfaces with Sanding Glass: A "sanding glass" (a piece of glass used with silicon carbide grit and water) is employed to smooth the bottom of the chamber and base, compressing the ceramic fiber layers.
8:04 Microwave Drying & Optional Blow Torching: The completed chamber and base are microwave-dried to remove moisture. Optionally, a blow torch can be used to harden the surfaces, with a warning to trim any burnt Kapton tape to prevent arcing.
10:02 Preventing Sticking with Kiln Wash: To stop the crucible from sticking to the chamber, a kiln wash is applied to the base. This can be a commercial product or a homemade mixture of Kaolin clay and aluminum oxide.
13:40 Optional Hardening with Boric Acid: A boric acid solution (5-10% in water) can be sprayed onto the ceramic fiber and then burned (producing a green flame) to further harden the surface, though over-application can lead to issues.
17:31 Making Crucibles (Glass Method): Silicon carbide powder is mixed with 8-10% sodium silicate (water glass) and compacted into a drinking glass. After shaping the interior, it's microwaved until the glass shatters, creating a "Stage One" crucible.
21:42 Making Crucibles (Freezing Method): Free 3D-printable molds (available on Patreon) are used with the silicon carbide and water glass mixture. The packed mold is frozen for several hours before being removed and hardened in an oven or by gradual low-power microwaving.
20:22, 25:01 Hardening Crucibles to Stage Two: For increased strength, crucibles from both methods can be wrapped in ceramic fiber and microwaved until they glow red, then allowed to cool.
27:26 Melting Efficiency Demonstration: Melting 24g of aluminum in a cold crucible takes approximately 4.5 minutes. The video demonstrates how placing microwave-absorbing materials like a fire brick inside the microwave drastically reduces melting efficiency.
29:11 Factors Affecting Melt Time: Melting times vary based on microwave power (which can degrade over time), crucible/chamber size, and the shape and type of metal. Aluminum typically melts in 5-8 minutes, brass in 8-14 minutes, with larger quantities taking significantly longer (e.g., 900g brass in 25-30 minutes).
32:07 Safety Considerations: The creator asserts that flipping a microwave on its side is safe based on personal experience. Microwave leakage detectors are an option for those concerned. Thin chambers are generally more efficient for quick melts. Arcing is uncommon when metal is contained within a silicon carbide crucible.
34:52 Importance of Personal Safety: While some demonstrations are done without gloves to show chamber efficiency, the creator strongly advises wearing gloves and appropriate safety equipment at all times when performing metal melting.