The effect of optical limiting is investigated in the suspensions of carbon
microparticles in aqueous gelatin gel and epoxy resin. Both transient and permanent
changes of optical transmittance are observed after the irradiation by a Q-switched
YAG:Nd³⁺ laser pulses. The experimental results are explained with taking into account
the formation of micro-bubbles filled with water steam and with gaseous products of
decomposition of the matrix. In the epoxy resin suspensions, the laser-induced permanent
changes of transmittance are caused by pyrolysis of epoxy oligomers in the vicinity of
laser-heated carbon particles.