Not 5 minutes later my costrel was well & truely cooked. However, one has to be philisophical about these things. I had learnt the hard way. My wife said "oh well, order a new one". But I could not give up that easily. So I set about trying to clean it out & reseal it with beeswax. This I have done, & only time will tell if it has worked.
The damaged costrel
The tin I used to melt the beeswax.
I only had to melt the wax once, & I was able to apply 3 coats of wax inside, swilling it about with the plug in place & pouring the wax back into the tin each time. Fingers crossed!