Two boxes with three types of paper were treated at the Di- Ethyl Zinc deacidification plant in Houston. These were part of a larger lot from the State Archives in The Hague. For the Central Laboratory, new, buffered photocopy paper, 19th century paper from a PTT (post, telephone and telegraph service) diary, and a number of pocketbooks, printed arounf 1950 on woodpulp paper, were treated. After treatment the paper was artificially aged over various peiods and examined using chemical, physic-chemical and physico-mechanical methods. The uniformity of the DEZ treatment was examined non-destructively using X-ray fluorescence. The research showed no influence on the aging properties of the new paper. The 19th centruy paper stood, after treatment, better up against accelerated aging. In the case of the woodpulp paper, only a minor improvement showed in the aging behavior. All types of paper were well deacidified. The uniformity of deacidification varied. The new buffered photocopy paper and the pocketbooks were evenly deacidified. The 19th century papere was sometimes good, other sheets less so. Probably this was caused by the heavy surface coating of this paper. The non-destructive x-ray fluorescence technique showed to be quite appropriate for a quick and accurate determination of the zinc content. In general, it cal be stated that the DEZ method is a good deacidification technique, where the uniformity of deacidification depends on the type of paper, but also on the way the paper is packed during deacidification. The research confirmed the results of the TNO project Effectiveness of the DEZ process: Evaluation with bound Dutch newspapers , TNO report nr. PK 93.1020, March 3, 1993.