You should not wash foam in a washing machine or soak a cushion unless an instruction allows it. 'Foam' refers to various materials and constructions, and a washable cover does not mean the contents can withstand the same treatment.
Find the manufacturer's information first. If the material cannot be identified, an assessment of made-to-measure foam and the existing cushion is a better next step than a test in the washing machine.
Distinguish between cover and filling
Check whether the upholstery can be removed, and whether it has a care label. Also look for intermediate layers or parts that are glued together. Take a photo before opening or moving anything, so the assembly can be put back together correctly.
A zip may be included for manufacturing purposes. It does not in itself document that all parts are designed for home washing.
Find the reason for the cleaning need
Is there a surface stain, a spill, dust or a persistent odour? Specify what happened and when. This determines whether the question concerns the upholstery, the core or the conditions around the furniture.
If a cushion becomes repeatedly damp from underneath, cleaning does not solve the cause. Placement, ventilation, or a leak must be investigated simultaneously.
Follow the instructions for the specific foam type
Carl Hansen & Søn advises against using solvents and steam cleaning on their upholstery foam. This is a good example that a method used on other surfaces may be unsuitable for a furniture assembly.
Do not combine cleaning products, high heat and harsh mechanical treatment on the basis of general advice. Confirm a suitable method before applying it to the whole cushion.
Drying must include the entire cushion
If the manufacturer permits wet treatment, the drying instructions must also be followed. A dry cover is not in itself proof that the core is dry. Therefore, do not pack a cushion away while there is doubt about moisture.
See storing cushions, when it needs to be stored for a longer period.
Assess replacement if material is degraded
Cleaning will not necessarily restore filling that is crumbling or permanently deformed. The guide to new cover or new cushions helps to define what can be preserved.
If new filling is needed, choose according to support, thickness and use rather than uncritically copying an old, compressed measurement.
