Modification of the the properties of ceramic masses depends on its application. Modifiers, apart from natural raw materials or chamotte, are usually substances with precisely defined properties that are constant over time. Modifications are made in different ways. The simplest of them, which causes an increase in porosity, is the addition of organic substances that will burn during the firing process, leaving empty spaces. The characteristics of the modifier (grain size, grain size distribution) determine what porosity will be obtained: spherical, longitudinal, or irregular pores.
The aim of the work was to determine how the addition of different amounts of coffee grounds affects the properties of commercial ceramic masses and their possible use in terms of 3D printing to obtain a material with high water absorption.
Coffee grounds are a waste that is being studied more and more widely due to their wide availability. Its use as biowaste is difficult because of the long fermentation time and the possibility of disrupting these processes due to the presence of organic compounds in this waste. In small amounts, they can be used as a fertilizer for plants, but a larger amount can interfere with their growth. Therefore, the literature is richer and richer in the results of work on other uses of this waste.
In the work, three commercial ceramic masses to which coffee grounds were added in three different amounts were tested. Coffee grounds were obtained as waste from coffee brewing (a mixture of Arabica and Robusta) using a pressure coffee machine. The masses were fired at four different temperatures and then their properties. The porosity, water absorption, shrinkage, mechanical strength, phase composition, and microstructure of the obtained samples were tested. Analysis of the results showed that the addition of coffee not only increases porosity but also significantly affects other properties, especially the phase composition of the samples.

The project was co-financed from the AGH UST Rector's Grant 2022 competition.