The Expansion-Contraction Process
The Expansion-Contraction Process
How foam volume shifts during molding — the step that's hard to copy
MIX
Stage 1
Foamable EVA + polyolefin elastomer + pigment combined
MOLD & HEAT
Stage 2
Mixture placed in mold, heated to activate foaming agent
EXPANSION
Up to 2.5x
Foam expands upon demolding, volume increases sharply
CONTRACTION
Factor of 0.6
Material cools and shrinks back, settling into final form
FINAL DENSITY
Stage 5
Closed-cell structure locked in, determines comfort and durability
Hidden variable: Different pigment colors expand at different rates. Mold dimensions must be individually calibrated per color — a detail refined only through repeated production, not published research.