The interpretation of the high-quality observations of the surface of TNOs provided by JWST requires new and refined laboratory data. In particular, infrared (IR) optical constants of ices are needed for models that simulate the reflection-absorption of sunlight on the surface of those objects. In this presentation, the main characteristics of the IR spectra of some ices of pure species and mixtures, already available in databases, will be given. In particular, the changes in the IR absorption features due to phase transitions, interaction with neighbor molecules in the ice matrices, or ice morphology will be discussed. To illustrate this, we will use some examples of the work previously performed in our laboratory (Maté et al. JPCA 2008, 112, 457, Gálvez et al. ApJ 2009, 703:2101). In a second part of the talk, the procedures to determine optical constants from IR absorbance spectra of thin ice layers will be described, stressing the main sources of error (Luna et al. A&A 2018, 617, A116). The importance of these magnitudes for the simulation of band profiles will be illustrated using as an example our recent publication where information on grain growth in the cold dense cloud Chameleon I was extracted from JWST spectra (Dartois, Noble, Caselli, et al. Nat Astron 2024. Doi:10.1038/s41550-023-02155-x). Finally, some ideas for future experiments involving different kinds of ice mixtures, oriented to the interpretation of TNOs surface observations will be discussed.