But a word of warning here. I used a flat pyrex baking dish dish to hold the foil, baking soda and water, and part way into the process of slowly simmering, it burst with a loud bang, and split into a number of pieces. I was fortunate that I wasn’t hit by the scalding water. I can’t say why the dish cracked as it did, but suspect that the metals (foil and silver) as great conductors of heat may have raised the dish to a temperature (at least in spots) that it would not have attained on its own. I would suggest using an old metal baking dish instead, something that you wouldn’t mind seeing blacked, should that happen.