I'm looking for information (from an expert) on restoring and protecting the varnish on an ancient tyrolean Double bass (17c Alban). I believe much of the original finish is present but there are numerous flaws including some places with bare wood. I would like to preserve and protect the varnish and improve the appearance. I understand that the work should be done by a competent professional, but I would like to be knowledgeable about the procedures. If any can suggest some literature to read or a professional to talk with I would be grateful.