Material most similar to today's paper is Papirus. Egyptians made papirus 4000 years ago using a plant called CYPERUS PAPIRUS. 200 years B.C. in Pergamon PERGAMENT was made. This material is considerd today to be the best material for writing with ink. Paper in today's form appeard in China around 105 years A.D. Mass industrial production of paper began in the first half of the 20 th. centuty. The most important raw materials for production of paper are : different sorts of wood pulp, tehnical cellulose, semi-chemical pulp and rag pulp. Paper is produced from pulp. Phases of preparing pulp are : dissolution and grinding of fibrous raw materials, mixing of different fibrous materials, addition of filler, addition of color and addition of sizing material. There are two ways of grinding : fast beating and wet beating. Paper is continuous tissue, composed of interwoven fibers of plant origin. By the term of paper we mean the sheets up to 150 g/m2 that well bend. There are different sorts of paper according to it's production procedure, composition of fibrous, surface treatment, use, adsorption, sizing and grammes per square meter. The topic of this work is dependence of pH value of office paper according to sample preparation. Seven different types of office paper have been used (Navigator, Rcopy, Fabriano, Xerox, Plano Premium, IQ i Pioneer). It was examined the impact of procesing paper ( with and without defibration) and time of mixing on pH value and conductivity of solution. Comparing the results it was concluded that time of mixing has a smaller influence on pH value of paper with defibration than of paper without defibration.