Pollution caused by the clean up of lithographic printing presses is a major problem faced by the printing industry. This paper explores alternate ink systems where the use of hydrocarbon solvents and volatile organic compounds (VOCs) for clean up is eliminated. The ink under consideration is a microemulsion, which can be emulsified in plain water-the property that can be used for its cleanup from presses. Furthermore, the washing is a completely physical process with no chemical reaction occurring thereby eliminating any salt streams. The ink washing commences in the form of tiny jets of water-soluble material vigorously coming out at the interface of the microemulsion ink drop and the wash liquid. Spontaneous emulsification is therefore proposed as the mechanism of washing. This paper discusses the ink formulation, its properties, and a model for spontaneous emulsification to explain its washing. The theoretical work is supported by experimental results. (C) 2004 Elsevier Ltd. All rights reserved.