How do I baseline correct when measuring a coating on a solid sample?

For solid sample transmission measurements, baseline correction generally involves measurements on air with no sample mounted.
However, to measure the transmission characteristics of only the film or coating on a substrate, before measuring the sample, perform baseline correction on a blank substrate with no film or coating applied.
As it may be impossible to obtain accurate measured results at wavelengths where the blank substrate exhibits high absorbance, it is extremely important to confirm the transmission characteristics of the blank substrate.