Ponencia presentada en el XIX Congreso Internacional de Acústica (ICA2007), Madrid, 2-7 Sep 2007.-- PACS: 43.35.Bf.The determination of particle size in suspensions is a relevant issue in many industrial applications, for which this size represent a quality parameter of primary importance. The use of particle size ultrasonic measuring systems is becoming widespread especially in those applications dealing with concentrate suspensions, where optic methods are less efficient. In this work, the analysis of amplitude and time of flight variations by means of pulse-echo a through-transmission techniques of different size and nature pigments and solvents is presented. Different frequencies and temperatures were used to detect variations of ultrasonic wave propagation characteristics in the suspensions. The preliminary results presented here show the viability of using the measurement of amplitude and time of flight to asses the quality of suspensions and therefore, to develop noninvasive and non-destructive methods to control the pigment production.This work was done with funding obtained from the CSIC by means of the project 200550F0190 during the joining of a pre Ph-D fellowship I3P financed by the Social European Fund.Peer reviewed