Fig. 4From: Non-invasive identification of polymers in cultural heritage collections: evaluation, optimisation and application of portable FTIR (ATR and external reflectance) spectroscopy to three-dimensional polymer-based objectsFTIR spectra for a CN box ATR clamped and handheld, b CN box ER and KKT, c CA sunglasses ATR clamped and handheld, d CA sunglasses ER and KKTBack to article page