Topic: Cause of Common Manufacturing Fault to Flower Frogs - Sowerby

[thomasandkatherine]

I recently received the question set out below regarding the common manufacturing fault found on the underside of the flower holes on english flower frogs or blocks, in this case a Sowerby frog.  Does anyone know the answer to the question, my guess is that it has something to do with the removal of the glass from the mould, but I am not sure:

"Got a question for you: 
underneath the frogs, on some of the holes, are odd-looking flakes, as if
someone shaved glass away.  The same effect as when a glass marble breaks. 
Can't be damage; because of the way frog is made, couldn't be impact chips
in the hollow. 

Do you have any idea what they are or why they're
there?"

[Lustrousstone]

They are there because the the holes were drilled through from the top when the glass is cold and not quite enough care was taken. The holes are only partly made in the mould. Creating moulds and processes for holes right through was more costly than a man with a drill. These were obviously perfectly acceptable at the time as were annealing flaws and shear marks.

[thomasandkatherine]

Brilliant, many thanks.  That explains partially drilled holes on some items also. Thank you again