Jim just read your post on 1/4 " at top of flask. From my
experience and what i have read you only want 1/4" to 1/2" of
investment over the top of your highest wax in the flask. also
be sure to scrape the top skin off the investment before burnout
as it tends to form a skin of airtight investment on the top as
the investment sets up. this makes it more difficult to draw
gases through either with vacume or centrifical.
Frank