Thanks for the heads up Martijn, I am actually going to perform a few small test runs and a project I have wanted to do for some time, I am going to fill a small mold with silver crystals, about 4 ozt. with a graphite lid on top, and see if this results in a better-looking bar, I am optimistic as to the results. I also have one of these on order as well, again, Thanks
If your purpose is to get a homogenous shiny bar, the most important is the heat profile you are following. Allthough this procedure is mostly working with gold, i am not 100% sure the same result will be achievable with silver.
The best result you can get is in a closed electric furnace with heat controller. Could work with gas furnace if you can control the flame (hmm could be a future project for me to try)
The heat profile is as follows:
Linear heating (start with low flame and increase the flame gradually, ex: if you can control it with a valve then small turns every 10-15 seconds) until you reach 1000-1050 C, you have to stay at this temperature a few minutes, then this is the tricky part since the cooling is the most critical.
Now for cooling you will do exactly the opposite but with even longer periods and smaller steps, ex: from 1050C you need to lower to 1047C stay 30 to 60 sec then lower the temp to 1044-1045C and so on...all until you go below 200C
Very time consuming if you`ll do it in gas furnace, with electric you can set the steps from the controller.
The crucible you use has to have a good closing lid which prevents air to enter and spoil your finish. All the time the furnace has to be air free.(as free as it can be)
I have experimented with this up until i broke my furnace (an old calcinating furnace) and still didn`t repair it..(well my kids use up all my time, so probably will
repair it in the distant future)
Good luck, it all goes by experimenting, but fast cooling always spoils the finish on the silver, no matter what process is used.