This morning I found a link that may be related to the borax and nickels thing: http://www.sparkbangbuzz.com/els/borax-el.htm
A great find! Here's Popular Science 1936 :
http://books.google.com/books?id=fygDAAAAMBAJ&pg=PA107&lpg=PA107&dq=borax+rectifier&source=bl&ots=Mk2XMdPw_5&sig=_ObzlgyVPwIypRMcsxAdt0qNcSk&hl=en&sa=X&ei=M8VtULzBMMHviQLl34HgAg&ved=0CFwQ6AEwDA#v=onepage&q=borax%20rectifier&f=false
So the "delay" is what they describe as "forming" (Recommended to use AC, per Jones Beene) after which it can be used for rectification and/or negative resistance.
Front page : http://books.google.com/books?id=fygDAAAAMBAJ&lpg=PA107&ots=Mk2XMdPw_5&dq=borax%20rectifier&pg=PP1#v=onepage&q&f=false
