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Residual solvent
Also known as: residual solvent, solvent retention, solvent odour, retained solvents, residual solvent test
Residual solvent is the amount of printing or laminating solvent left in packaging after drying; too much can cause odour and taint.
Residual solvent is the small amount of solvent from printing inks, lacquers and adhesives that remains in packaging after drying, usually expressed in mg/m².
Where it comes from
Gravure and flexo inks are often solvent-based, using solvents such as ethyl acetate or ethanol that are evaporated in drying units. Solvent-based lamination adds more. Drying is never total, so the goal is to keep what remains low.
Why it matters
- Odour and taint: chocolate, coffee, dairy and fatty foods pick up off-odours easily.
- Food safety: residual solvents can migrate, so they form part of the food contact assessment.
- Bond strength: trapped solvent can interfere with adhesive curing.
Measuring and reducing it
Residual solvent is measured by gas chromatography on a heated sample. There is no single legal limit; converters and brands work to agreed internal specifications. Good drying, sensible press speeds, solventless lamination and adequate reel airing all help. If your product is odour-sensitive, say so when requesting a quote and ask what residual solvent checks are performed on each batch.
Frequently asked
Is there a legal limit for residual solvent?
Not as a single universal figure; the industry uses agreed specifications, and residual solvents are also considered in the food contact compliance assessment.
How is residual solvent tested?
Usually by headspace gas chromatography, where a sample is heated in a sealed vial and the released solvents are measured.
Related terms
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