Definition
A colorless, fast-evaporating organic solvent (chemical formula C4H8O, also called butanone) used in aviation maintenance to clean, degrease, and prepare metal and composite surfaces, and as a thinner or activator in certain paints, dopes, and adhesives. It is highly flammable and produces vapors that are harmful to inhale, so it must be used with ventilation and proper personal protective equipment.
Plain English
A strong, quick-drying cleaning and thinning liquid used in aircraft shops to wipe surfaces clean before painting, bonding, or sealing. It evaporates fast, catches fire easily, and the fumes are not safe to breathe without good airflow.
Context Anchor
Seen in aircraft maintenance manuals, shop procedures, material labels, and safety instructions for cleaning or preparing parts.
Derivation
The name describes its chemistry: a 'methyl' group and an 'ethyl' group attached to a 'ketone' (a type of organic compound). Knowing it is a ketone signals that it behaves like acetone — a strong, fast-evaporating solvent — which matches how it is used in the shop.
Why Pilots Care
Maintenance technicians and owner-operators handling paint, fabric covering, or composite repairs need to know MEK is both effective and hazardous. Improper storage, poor ventilation, or using it near ignition sources can cause fires or health issues, and using the wrong solvent can damage finishes or weaken bonded repairs.
Intuition Check
MEK is not just a stronger household cleaner. It is an industrial solvent that can burn easily, give off harmful vapors, and affect aircraft materials if used in the wrong place.
Example Sentence 1
The technician wiped the aluminum panel with MEK to remove oils before applying the primer.
Example Sentence 2
MEK dries quickly so the mechanic could reinstall the cleaned fuel lines without delay.