Discussing deacidification with a group of colleagues, the writer came to the conclusion that there is no standard answer on what to use or when to use it. There are degrees of treatment, ranging from washing with deionised, alkaline water, ph 7-8, or the same with more calcium bicarbonate solution, or magnesium methyl carbonate (non-aqueous). Choice depends on the type of object and its possible susceptibility to treatment, the environment to which it will return, the aesthetic effect of any possible treatment, and finally the function of the object (it is likely to be used or simply looked at?) it is emphasised that all three treatments listed above are irreversible major interventions and should not be undertaken without considering the above factors.