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NightHawkInLight shows how to make radiative sky cooling paint from grocery and hardware store materials, including a novel calcium carbonate microsphere synthesis. The paint can cool a surface below ambient air temperature in direct sunlight without electricity.

A beginner-focused tutorial on freehand knife sharpening with a single stone, aiming for a shaving-sharp edge in about five minutes.

This Old House's Ross Trethewey explains MERV filter ratings and how air filtration works, then shows how to build a localized DIY air filter, including a box fan with multiple filters.

Matt Risinger covers installing a Zehnder ERV fresh-air system in a tight passive house, explaining balanced ventilation, the benefits of heat recovery and the costs involved.

A roughly three-hour screen recording of designing a barebones STM32F4 board in KiCad, covering schematic, four-layer layout and routing, USB and a buck converter. It ends with ordering manufacture and assembly through JLCPCB.

Ben Vallack walks through designing a custom keyboard PCB from scratch using Ergogen and KiCad, ending with a gerber file ready to order from a PCB fabricator. The example is a split keyboard.

Big Clive shows how to pick up discarded disposable vape devices from the roadside and extract the rechargeable lithium cells inside. He explains why these devices contain the same circuitry as rechargeable ones and how to reuse the cells.