Abstract: The present invention relates to a gel comprising A) a solution of at least one organic peroxide essentially solubilized in a phlegmatizer, B) at least one cellulose ester as thickening agent essentially solubilized in solution A, and C) at least one thixotropic agent selected from hydrogenated castor oil and fumed silica. These gels offer the advantages of essentially no phase segregation during storage, essentially no formation of solid crystals during storage, and easy metering into thermoset resins because of their thixotropic behavior. Furthermore, these gels may be transparent, with the advantage that brightly colored gels may be prepared therefrom.