The ashes are primarily bone ash, calcium phosphate. The sodium
content won't be high enough to give you a problem.
The May issue of Ceramic Monthly includes an article by Jeff Zamek
entitled "Black Friday". It tells about his using the ashes of his
Black Lab to glaze a coffee mug -
http://www.ceramicsmonthly.org/issues/2001-05/friday.asp. The article
is also included in his book, "What Every Pottery Should Know". He
includes the recipe for the glaze he used, but it's cone 6.
deg