[Thermal Mass]

Thanks! Looks awesome.
I had never heard of Sumac (except the poisonous stuff) either, but will definitely be giving it a run. The wheels are really turning now.
Here is what Penzy's has to say about their product:
Sumac
Cherry red sumac is used extensively throughout the Middle East, especially in Turkey, Syria and Lebanon, either plain or mixed with thyme leaves and sesame seeds (Zatar) as a tabletop condiment. Before the arrival of lemons in Europe, the ancient Romans used sumac for its sour flavor. In the Mediterranean region today, sumac is used as a tabletop condiment or added during cooking to lend a pleasant, fruity sourness and soft cherry color to sauces, poultry, fish, and Turkish salads. The flavor is on the order of lemon juice or vinegar but milder and less acidic. Because of the moistness of the fresh, whole sumac berries, a small amount of salt is added during processing to facilitate grinding. From Syria. Contains Sumac and Salt.

Thanks Titch!