The reason you cannot use any paddle to mix any material is that each paddle has a unique design that makes it suitable for its particular job.
A paddle’s construction can mean it’s suitable for heavy duty work (e.g. professional steel paddles) or it can be made to suit smaller volumes of material (e.g. aluminium paddles)
Steel
Steel is a mixture of iron and carbon, which are its alloy elements. Steel is well known for its strength, which is given by these elements.
Steel is stronger than aluminium, however, both are strong materials used to construct a number of mixing paddles.
Aluminium
Aluminium is a relatively durable, lightweight, and malleable metal. It is used to make some heads of mixing paddles. Aluminium can be easily bent or damaged if used incorrectly or not properly maintained.
Hardwood
This is wood from a broad-leaved tree such as oak, ash or beech. Hardwood is not always ‘hard’, and each type has its own set of properties; some even have properties in common.
Hardwood is used because of its density and the fact that it does not rot or decay easily. It is used to make the handles on some mixing paddles.