[Sca-cooks] Recipe for Making Isinglass?

[Elise Fleming]

Greetings.  We are looking for a recipe to make isinglass from fish
bladders.  Can anyone provide a period source?  We've found lots of
recipes _using_ isinglass but none that actually make it, although
Master Patrick McPhelan says he recalls seeing one.  He and I have
searched through all our cookery books and have come up blank.
Can anyone help?

Alys Katharine, on behalf of Master Patrick