Handle before cleaning
Wash and dry your hands, clear the work surface and support the whole puzzle when lifting it. Do not pull a projecting piece unless you know it is intended to move.
Avoid unnecessary products
Do not apply oil, polish, wax, water or solvent simply because a mechanism feels tight. Finishes, adhesives and mixed woods may react differently, and added material can attract dirt or swell joints.
Control the environment
Store away from radiators, damp walls, direct sunlight and rapid changes in temperature or humidity. Keep every loose piece together in a labelled, breathable container.
When a puzzle becomes tight
Stop and check the solution, grain direction and possible damage. Allow a recently moved puzzle time to acclimatise. Never use pliers, hammers or excessive leverage.
Record condition
Photograph cracks, lifting veneers, loose joints and missing pieces before intervention. Valuable or historically important objects should be assessed by a conservator.