When customers first try foam-in-place packaging, the most common question is: why does one foam feel soft and another feel firm? The answer is foam density. Choose the right density and you get the best protection at the right cost; choose wrong, and you either under-protect your product or overspend. Let us explain.

Foam density is simply the weight of the cured foam per unit volume, determined by the formulation and the amount of A/B material dispensed. More expansion means lower density and a softer foam; less expansion means higher density, a firmer foam and stronger support. Cosmolar foam-in-place packaging offers three densities—6/17/23 kg/m³—each matched to a typical protection need.

6 kg/m³, soft foam, for light and delicate items. LED lights, crafts and small instruments are light and scratch-prone; a soft cushion wraps them gently without adding weight to the carton. Cosmolar hand foam bags use a soft formulation by default—ideal for small shipments, samples and after-sales replacements, with no machine required.

17 kg/m³, balanced and versatile, for most industrial parts. Auto parts, pumps and valves, motors and transmission components need a cushion that is neither too soft nor too hard: enough resilience to absorb impact, enough support to prevent shifting inside the carton. This is the most-used formulation for Cosmolar semi-automatic machines (CM-811/CM-816) in small-to-medium batch production.

23 kg/m³, firm foam with strong support, for heavy and large parts. Machinery, large hardware and precision machine accessories are heavy and generate strong inertial forces in transit; high-density foam provides rigid support so the product never punches through the cushion layer. The fully automatic CM-812 handles high-density formulations consistently on high-volume lines.

How do you know which density fits your product? Test it. Cosmolar offers free sample testing: send us your product or try on-site packing, run drop tests on different densities, then finalize the formulation based on daily output and packaging cost. Density is not about harder or softer being better—it is about fitting your product.

Density selection is just one step of a custom foam-in-place packaging solution. Share your product photos, weight and daily output with Cosmolar, the source factory for foam-in-place packaging, and we will configure density, bag type and machine together—sampling first, quotation second, volume production third: https://www.cosmolar.com/