Glass needs to be clean when it comes in for repair because it is not the glassblower’s job to clean the glass of a dirty consumer. If the customer does not have the pride or respect to clean their piece we can not help them.
Dirty glass will cause it to melt very badly during the repair, and since we know this, we will not repair the dirty glass.
Also, who would bring in their piece filled with germs and dirt to anyone they would ask help for.