Home built paint can furnace 2020

This furnace is made from a 10 liter (2.1 gal) paint can purchased for $10 at the local hardware shop. It is lined with Fiberfrax (a kind of Kaowool) and the Fiberfrax is lined with Fermit, a 1600°C rated according to the label on the bucket (the site says 1250°C) refractory cement. But earlier tests revealed no melting or softening happened at 1550°C. I got a few 3kg buckets of $11 eacht via Amazon. It is lined by making a kind of porridge with water of it and applying it with a paintbrush to the inside of the furnace. The bore is about 15cm / 6" and the bottom is a cell concrete block lined with the same blanket and coated with Fermit as well and an upside down old crucible resting on the solid floor is used as a fixed plinth. I ran this furnace many times for iron casting and it reached 1500°C within 15-20 minutes with a full crucible (0.8-1kg) of cast iron. But I had no proper lid so I just put a blanket on top to keep the heat inside during melting.

In july 2020 I made a lid from chicken gauze filled with leftovers of Fiberfrax and coated it with a thin layer of Fermit. On the inside I made a collar of Fiberfrax attached to the lid which is also coated with Fermit. I did a dry run with the new lid and it withstood the heat very well.

Photos of making the lid and testing of the furnace July 2020

Furnace and lid just coated with Fermit	The under side of the lid	First test fire with this lid, about to ignite
Five minutes: 1200°C	After 20 minutes: well over 1500°C, (blanket still over exhaust)	Underside of lid after firing
Furnace after firing	Detail inside furnace