or equal to 470 u00b0 c and preferably of less than or equal to 450 u00b0 c as well as good producability and processability and crystallization stability application_number US 58619806 A description with the u201c inner quality u201d of a glass is meant according to the present invention that the glass contains a proportion of bubbles and or strias and or similar defects which is as low as possible respectively preferably that it does not contain such defects at all in the following the term u201c x free u201d or u201c x free u201d respectively u201c free of a component x u201d means that the glass substantially does not contain this component x i e that such a component is only present in the glass as an impurity however that it is not added to the glass composition as a single component here x represents an arbitrary component such as for example f in the following all proportion data of the glass components are given in by weight and are based on oxide unless otherwise stated the basic glass system of the glass according to the present invention is a germanium oxide containing bismuth oxide glass having a ratio of both components bismuth oxide to germanium oxide of at most 5 which is a good basis for the desired properties the glass according to the present invention has a proportion of bi 2 o 3 of at least 55 by weight preferably of at least 56 by weight particularly preferably of at least 57 by weight the proportion of bi 2 o 3 is at most 70 by weight preferably at most 68 by.