The radiative properties of plasmas are governed by opacity and emissivity. Accurate determinations of these quantities are of relevance, therefore, to inertially confined nuclear fusion (particularly indirect drive schemes) and to resolving discrepancies between the observed behavior of astrophysical plasmas and theory. This work summarises achievements in the field over the last few decades. It also presents the results of experiments to (i) determine the opacity of warm to hot, dense iron plasma and (ii) investigate laser ablation rates using the transmission through sample targets of x-ray laser pulses. These results are compared with the predictions of computer simulations. Laser ablation rates are of relevance to direct drive nuclear fusion and other technologies such as laser welding and materials deposition. Experimental work was undertaken using a nickel-like silver x-ray laser (XRL) of 13.9 nm wavelength at the Rutherford Appleton Laboratory and a 21.2 nm neon-like zinc XRL at the Prague Asterix Laser System.