Abstract Several antireflection treatments such as Teflon dipping, dipping in silica saturated fluosilic acid, have previously been tested. The films made with the fluosilicic acid showed an increased solar transmittance of up to 5%. Outdoor testing for more than 7 years indicated an excellent long-term stability. The problem with this process is the involved chemicals, which are too harmful to permit a large-scale production in Sweden. Therefore, a dip-coating process has been investigated, which uses silica sols. Two sols were investigated, one polydisperse and one monodisperse. The highest attained solar transmittance was achieved with the monodisperse sol. It is believed that the increase in the solar transmittance is connected to the size of the silica particles, the larger the smallest particles the higher the solar transmittance. A decrease by up to 5.2% in the solar reflectance has been noted. A problem is the mechanical properties and especially the adhesion tends to be low. It is, however, possible to improve these properties by baking the film at approximately 550°C during 30 min. The solar transmittance decreases when baking the film since it collapses partially, but the mechanical properties seemed to improve. During baking the temperature is close to that of commercial tempering. It should therefore be possible to bake and temper at the same time. The deposited film does not introduce any absorption. It is concluded that this process should be suitable for large-scale production, since the involved chemicals are harmless and the process is fairly rapid. Films were made at withdrawal rates of up to 1 cm/s.
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