Salaried labor is a fixed cost. Hourly labor is a variable cost. Spoilage is a fixed cost.
Fixed costs AND variable costs grow as the company gets bigger. Please don't get confused by the word "Fixed". Fixed costs are not immovable...if I change my marketing budget, the costs change! If I build a new factory to produce more goods that capex fixed cost changes!
A variable cost is one that changes for each additional unit produced. A fixed cost stays fixed for a given incremental increase in productions.