Retarder can be redissolved within approximately 1 hour of drying by applying water or fresh colour. The re-dissolvability time depends on individual drying factors (ambient temperature, humidity of the air, etc.). Lascaux Retarder is not recommended for use on porous supports, nor for exterior applications.
The Retarder can be added to original colours in a pro-portion of 10 to 30%, either undiluted or diluted with water as desired (up to 1 part Retarder to 10 parts water). The slow evaporation the complete drying time is greatly extended especially if there are several layers. The paint may stay soft and susceptible to water for a considerable time. The use of Retarder is therefore not recommended for outside work, since the longer drying time increases the risk of swelling through contact with water (e.g. rain).