The Voyage Is a Test You Did Not Design
Humidity is the slow variable
A container cycles through temperature and humidity swings that indoor packaging is never tested against. Barrier bags with a proper moisture barrier are specified for moisture-sensitive devices for a reason; an ordinary shielding bag slows vapour transfer but does not stop it. Where the consignment includes moisture-sensitive items, the bag spec, desiccant and humidity indicator cards should be treated as one system, not three afterthoughts.
Cartons should also survive condensation on the outside. Kraft over foam that wicks moisture can arrive soft; a liner or a moisture-resistant outer layer is worth specifying for sea legs.
Time, dwell and what foam remembers
Foam under load remembers: a cavity insert crushed under stacked cartons for six weeks at deck temperature may not spring back the way a bench sample did. Review stacking orientation so the insert carries load the way it was designed to, and check compression-set behaviour for the chosen foam grade when long dwell under load is expected.
Finally, plan for inspection at the destination. Marking cartons so the first-opened box is the one with humidity indicators makes acceptance checks faster, and giving the receiver a one-line instruction on what to look for prevents a "readings changed" dispute from becoming a claim.
FAQ
Is a shielding bag enough for sea freight?
A shielding bag protects against electrostatic discharge but only slows moisture transfer. For moisture-sensitive devices, a proper moisture barrier bag with desiccant and humidity indicator cards is the standard system.
Why do cartons need a moisture-resistant outer layer at sea?
Containers see condensation cycles. Kraft or paper outers that wick moisture can arrive soft and lose stacking strength before the goods are unloaded.
Can foam inserts be crushed during long voyages?
Yes. Foam under sustained load and heat can take a compression set, so stacking orientation should let the insert carry load the way it was designed.
How do we speed up acceptance checks at destination?
Mark the carton containing humidity indicator cards as the first to open, and give the receiver simple written criteria for reading them.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.