Scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDX), Fourier transform Infrared (FTIR), Raman microscopy and X-ray photo-electron spectroscopy (XPS) methods were used to assess the penetration of deacidification solutions of magnesium methoxymethylcarbonate (MMC) in methanol and trifluorochloroethane applied to new and aged primed linen canvase. Differences in penetration were observed by the distribution of magnesium (Mg) and these were related to method of application in order to devise better procedures and understand the likely protection provided. Conditions varied from excessive accumulation of Mg on the reverse to salts being deposited on the front by passage through cracks in the priming.