The author critically reviews accepted processes for deacidification of paper with special reference to Langwell's improvement on the ammonia method. We are reminded that in the Vapour Phase Deacidification process book become deacidified in about two week by interleaving with sheets impregnated with cyclohexylamine carbonate, and the contents of typically sized archival boxes require 6-8 weeks. The VPD process compares unfavourably with the Barrow method of spray deacidification, using concentrated magnesium bicarbonate with 25% ethyl alcohol, because CHC does not leave a permanent residue of basic material in the paper. The author notes the use of different methods to age paper and to measure its pH. He stresses the need for standardization, and suggests comparison under standard test conditions of VPD with known wetand spray processes of deacidification. 6 tables.