- Material sciences and production techniques -


research project 1994-1997
The project aimed at developing a method for utilizing waste glass by sintering and pressing fine ground glass. The main part of the project (1994­1995) was financed by the Technology Development Center of Finland TEKES and it was carried out in cooperation with YTV, Helsinki Metropolitan Area Council, Tampere University of Technology and Suomen Erikoismurskaus Oy, Siilinjärvi. Two researchers, Päivi Kekäläinen (UIAH) and Markku Rajala (UIAH), were working on this project from March 1994 until the end of 1997 in several periods. 

The results indicate that sintered glass is a noteworthy material for facing tiles or other clinker applications. However, the results the project produced are preliminary and are not yet sufficient for building up actual production. 

In the sintering and pressing process, first the glass is ground to a fine powder (particle size under 0,5 mm) and mixed with a binder. The mixture is portioned out into a metal die and pressed (300­500 kg/cm2). The pressed article is removed from the die and fired in a kiln to the sintering temperature, 700­900°C. The result is hard, somewhat porous glass. It is not transparent or does not otherwise look similar to molten glass. 

The conventional policy to utilize waste glass is to melt the glass and manufacture packages, glass fibre, etc. Using the sintering process it is possible to achieve several advantages over melting glass. Sintering takes place at 700­900°C, whereas melting the glass requires about 1400°C. This means considerable savings on energy costs. Due to the lower temperature, the expenses of the kiln materials are also lower. Recycled glass often contains some impurities, metal etc. This is a problem when processing molten glass. A sintered glass structure will bear impurities both technically and aesthetically. 

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Päivi Kekäläinen, @
Markku Rajala, @

University of Art and Design Helsinki UIAH
Department of Ceramics and Glass
Hämeentie 135 C 
FIN-00560 Helsinki, Finland 
fax: +358 9 75630275