The present invention relates to a method of manufacturing heat sensitive recording material for the bar code reader wavelength range of 660-690 nm, the recording material containing a base layer and a coating, and the coating containing at least a color former and a developer. The method of the invention is characterized in that the color former and the developer are selected so that when the reflectance of the color former-developer compound on the recording material is determined, it remains below a target curve determined with a function Hp=1.775*Ap^22*10^-61, where Hp is the reflectance percent and Ap the wavelength (nm) used in the bar code reader.