Parallel versus Tapered Threads

Threads

Limescale Removal

Calcium carbonate (limescale) dissolves in a range of mild acids.

Rust and WD40

WD40 stands for Water Displacement, 40th attempt (name used by the chemist who developed it in 1953). Norm Larsen was trying for a formula to prevent corrosion, achieved by displacing water. WD40 has no expiration date. It also cleans and degreases and can be used to lubricate the chain on a bike. WD40 cans contain carbon dioxide as a propellant.

You can remove rust with a wire brush and coat with WD40 to prevent rust.

Soap

The earliest evidence of soap-making comes from Ancient Babylon around 2800BC. A formula for soap consisted of water, alkali and cassia oil ("false cinnamon"). Recipes for soap have existed through the centuries. Only till about the 1850s did industrial production of soap commence. The Latin word "sapo" means soap.

Industrial Uses of Gold and Recycling

Gold has some useful properties that make it usable in electronics. Gold is highly conductive (lots of free electrons) and also resistant to corrosion and oxidation. Some people have tried to remove gold from household electronics.

Some experiences:
"I am using nitric acid and getting a good amount of what looks like gold"

What is Chicken Stock?

Chicken stock is the remaining water in which you boiled chicken, containing fats and oils. Sometimes used to cook rice.

Rowing Machines

Rowing machines, intended to simulate the sport of rowing, come in many shapes and sizes. The most common ones use "air pressure". They tend to be fairly noisy. You also get rowers with water resistance or magnetic resistance (the most quiet). You should always warm up before using the rowing machine, including lower back exercises. When rowing keep your back straight. Rowing hard at high resistance will increase shoulder size.