Why container cartons are vulnerable
A carton of heavy goods is supported by its contents: stack another carton on top and the load goes through the product. A carton of nested thin-wall takeout boxes, PP cups or empty storage bins has almost no support inside. The product is mostly air, it flexes under load, and the carton walls carry nearly all of the weight from above. When the carton gives way, the product inside takes the load and deforms or cracks.
At the same time these goods are shipped in large volumes. Because they are light and bulky, freight is charged by volume, so buyers and plants are tempted to fill every centimetre of a container and stack cartons as high as the space allows. That combination of tall stacks, weak support and long transit is what produces crushed cartons.
Pack count and how it affects strength
Pack counts in partner plant materials give a sense of the range. PP thermoformed takeout boxes, soup cups and starch-based bowls are typically packed 200-300 sets per carton. Injection molded PP cups are packed 300-500 per carton; one reference is 500 cups in a 41x32x48 cm carton. PET cold cups run around 1,000 per carton and sauce cups 2,000-5,000. Storage boxes and organizers are packed in much smaller counts, often a few units per carton, sometimes assembled and sometimes flat.
The pack count decides how tightly the product fills the carton. A carton with a gap at the top lets the lid flap sag and the walls bow; a carton overfilled so that it bulges loses most of its stacking strength because the walls are no longer straight. The right count fills the carton snugly without pressure. The packing counts and carton specs note covers how to set them.
Carton grade and humidity
Export cartons are usually corrugated board, and their stacking strength depends on the board grade, the flute and the quality of the paper. A cheaper board saves a little on each carton and can cost the whole shipment. Humidity is the hidden factor: corrugated board absorbs moisture and loses a large part of its strength in damp conditions, and a sea container crossing warm, humid regions is damp for weeks. Cartons that pass a stacking check in a dry plant can fail at sea.
The desk asks for the board grade to be stated in the order and, for new programs, for burst and edge crush results and a stacking check on the packed carton. These are the carton tests listed in the standard inspection items; counts and pass criteria are a stated working default and are confirmed per order. See testing and inspection.
Stack height and the load plan
Stacking strength is only meaningful against a stack height. A carton that holds four layers safely may fail at seven. The load plan should state the maximum stack, whether cartons are palletized or floor-loaded and what else shares the container. In consolidated LCL shipments, other shippers' heavy goods can end up on top of light packaging cartons; marking cartons clearly with stacking limits and fragile labels helps, but in LCL there is less control. Sea transit typically takes 15-25 days to the US West Coast and 30-45 days to Europe, which is a long time under load.
Palletizing adds protection: corner boards, a top sheet and stretch wrap spread the load and keep cartons square. It takes some volume, so the trade-off between pallets and floor loading is worth checking against the freight cost. The packaging and palletizing and logistics and shipping pages cover both routes.
Packing inside the carton
Inner packing matters as much as the carton. Nested takeout containers in sleeves of a sensible height resist crushing better than one long stack. Lids packed separately keep their shape. Storage bins can be nested with a top sheet so the upper bin does not take the load directly. Assembled organizers and drawer units need dividers or inner boxes so the units do not press on each other. Paper gift boxes and folding boxes from the printing cluster around Longgang are usually shipped flat, which is efficient but needs a stiff carton so the flats do not bend.
Diagnosis table
| Symptom | Likely cause | Check | Fix |
|---|---|---|---|
| Bottom cartons crushed, top fine | Stack too high for board grade | Stacking check at stated height | Stronger board or lower stack |
| Cartons soft and bowed on arrival | Humidity weakened board | Compare dry and humid stacking | Higher grade board, pallet wrap, desiccant where used |
| Carton tops sagging | Pack count leaves a gap | Open a packed sample carton | Adjust count or carton height |
| Carton sides bulging | Overfilled carton | Check carton squareness | Reduce count or enlarge carton |
| Damage only in LCL shipments | Heavy goods stacked on top | Ask the forwarder for load photos | Pallets, clear marks, FCL where volume allows |
| Products cracked, carton intact | No inner support, impact damage | Drop test on packed carton | Sleeves, dividers, top sheets |
What to put in the order
- State the pack count, carton inner size and board grade for each item.
- Agree carton tests: burst, edge crush, a stacking check and a drop check on the packed carton.
- Set a maximum stack height and decide between pallets and floor loading.
- Specify inner packing: sleeves, separate lids, dividers, top sheets.
- Require stacking and orientation marks on every carton.
- Ask for loading photos from the plant or forwarder.
Balancing freight cost and damage
Every packing upgrade has a cost in material or container space, and every damaged carton has a cost in replacement, freight and customer goodwill. For most container programs the right answer is a moderate upgrade: the correct board grade, a sensible stack height and good inner packing, rather than the maximum load. Nesting design also helps, because a product that nests deeply puts more pieces in each carton without raising the stack. The desk compares options on the packed sample before the first shipment.
Next step
Packing changes can affect the carton count per container and therefore the order plan. Starting quantities and lead times are on MOQ and lead time. To review a damaged shipment or plan a new one, send carton photos, the pack count and the load type through the quote form.