Tracy, did you manage to find a supplier for hartshorn?
I noticed that it's fairly easy for me to find, in my area, but I also found a site that sells it for a lot less than an arm and a leg.
This is this month's newsletter:
http://www.kitchenproject.com/GermanGoodies/Notes/
This is the page for ordering the hartshorn:
http://www.mcssl.com/SecureCart/ViewCart.aspx?referer=http%3A%2F%2Fwww%2Ekitchenproject%2Ecom%2FGermanGoodies%2FNotes%2F&mid=088CB691-847D-43BE-9C84-0A39137E5F82&pid=60b2e1b97d9911c9d5745fdbab40425f&bhcp=1
and this is the page for some baking ammonia/hartshorn recipes:
http://www.kitchenproject.com/german/recipes/Cookies/Hartshorn.htm
ViolaB