The bolussen are done when they sound hollow when you tap the bottom.
The milk in which the yeast is dissolved can’t be warmer than 50 °C.
The name blos is derived from the Jiddish, the language spoken by the European Jews and that has itself taken quite a few words from other languages. The bolus or boles is the plural form of bole, which is derived from the Spanish bollo meaning ’fine bread bun’.