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We experimentally investigate the properties of crystalline 3D Weaire–Phelan foam structures as photonic crystals. We generate templates on the computer and use direct laser writing (DLW) lithography to fabricate foam designs in a polymer material. Due to the complicated structure of the foams, conventional DLW does not offer the resolution to produce systems with a stop band for telecommunication wavelengths. We employ shrinkage by thermal processing to circumvent this problem and show experimentally that foam Plateau border networks built in this way provide a stop-band within the wavelength interval of λ = 1–2 μm, with the specific wavelength dependent on the degree of shrinkage. We also investigate the dependence of the position and strength of the stop-gap on the solid filling fraction. [ABSTRACT FROM AUTHOR]