Our Attempts At Cleaning So Far

AS far as cleaning is concerned, discretion rather than valour may be better applied at this point. So far I think you have done really well with them.

It is my opinion that these coins have sustained corrosion before you ever got to them. I do not think that extra chemical cleaning will help.

The next step will require considerable patience and skill. Picking at them now using an orange stick, and vision assisted with a loupe, seems to be the next move.

Do a screen dump of the pictures you have taken to assist.

I like the theory, but from my experience, it was a disaster.

I tried that once. I heated a late Roman bronze to the point where I could just handle it with my fingers, then plunged it into cold water.

The result?

The coin just broke up into a jillion little particles.

The metal for a coin comes out of the ground. That is exactly where the result of my little experiment ended up.
"From dust to dust, ashes to ashes."

I really do not think heating / cooling, OR cooling / heating with ancient copper silver or bronze coins is a good idea. I found out the hard way.

From what I can surmise, there is a great probability that corrosion products at least to a minor extent, can effuse themselves right through the body of a bronze coin. If that has in fact happened during the last 1600 years or more, and you attempt to heat or cool it, there is a very risk of disaster, as I found out for myself.

You just have no way of knowing the extent of chemical degradation of the body of the coin before you start heating or cooling it.

Degradation of the body of ancient silver coins has a different cause. Quite often after an ancient silver coin is struck, a very slow natural crystallisation process can start, which affects the whole body of the coin. This is why some ancient silver coins are chipped. I would imagine that an ancient silver coin that is subjected to severe cooling or heating may spontaneously break up as well.

I certainly would NOT contemplate the risk.

WOW it broke on the carpet?!! I would have been both shocked and devastated. In my experience of heating ancient bronze coins, I have done it a few times in the oven @ 450 degrees, Out of the 20 or so coins that I have finally made it to the baking process, I lost 4. One crumbled in my hand, the others just cracked and the metal began to flake off in clumps. Not a good idea- this process should be avoided, unless you are treating bronze disease on a small effected area. IMHO.