Star Seal vs Flat Seal: Which Base for Which Waste?
The engineering difference between seal types and when the extra cost of star seal pays for itself.
4 min · 2026-10-13
How the two bases actually fail
A flat (or gusseted) seal joins two or more film layers in a straight line across the bottom. Load concentrates at the two outer corners. Sharp or wet waste finds those corners first. A star seal gathers the tube into a multi-panel base so the bottom is more three-dimensional and the stress is shared.
Star seal also tends to sit flatter in a bin, which reduces side-wall stretch on first fill. That is why many retail can-liner programs default to star seal even when the micron is modest.
When flat seal is still the right call
Flat and gusseted seals remain common for large industrial sacks, square cartons of folded bags, and SKUs where the buyer already has a packing pattern built around a rectangular base. They are also simpler to inspect on a line and can be cheaper at very high gauges where the film itself carries the load.
If your waste is dry, bulky and not dropped from height, a well-specified flat-seal HDPE sack often outperforms a thin star-seal liner on cost per kilo of waste moved.
Specifying it in the order
Write the seal type on the technical sheet: star, flat, gusseted, or bottom-weld with side gusset. Add leak test method if the bag will hold liquids. Do not assume “star seal” from a product photo — packing photos can hide a gusseted fold.
For mixed retail + industrial tenders, run two SKUs rather than forcing one seal onto both jobs. The extra SKU usually costs less than field failures and claims.
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