Blisters in an ingot

I poured about an 85 gram ingot that was 5mm thick by 4" long. After sanding it down smooth and forging all the sides, I rolled it out to about 12" X1"X18 gage. It is all smooth with no fissures, but there is a small area with what look like blisters that appear after annealing. They are on both sides. This happens from time to time and I just roll them down and am careful how I use the piece in finishing. I decided today to cut out this section and do an experiment soldering and finishing a piece from this section so that I can see how it behaves. See the attached picture. Does anyone know what the blisters are or why they happen? The scrap is all clean with solder removed, a magnet used to remove any ferrous bits and the ingot was annealed often.

It’s been interesting to be stuck at home with all of my retail shops closed and no web traffic. I have been able to try some things that I would normally not have had time to do, clean benches, restock chemicals and do the experiment described above. I hope that you are all coping with this mandatory down time and able to stay safe, sane and healthy…Rob

Air pockets. They happen when the molten metal is not poured smoothly and fast enough.
If you plan on using the metal to fabricate with they will pop up again after soldering. Looks like you may have to start over or just cut away the air bubble areas and just remelt those bits in another ingot.

Jo…Thanks! What you say makes a lot of sense. They pop again after annealing. Thinking back, I didn’t tip the mold before pouring. I usually do to help get the air out. I cut out this small section to experiment with. I made three pair of earrings that turned out OK. One had a small void that I was able to work around. Thanks again…Rob

Glad you were able to salvage enough of the metal to make some jewelry.

That same thing happened when I annealed and rolled out 10 oz bars of A-MARK .999 fine silver. Only on one one side so just used that on the back of pieces I chase and repose.

The rolled ingot is about 12" long and 1" wide. The section with the blisters is about 1" X 1.5". I was able to work around the blisters and made some earrings that I have been thinking about. They are in the attached picture. While my stores are closed and there are no sales or orders coming in, this shelter in place has allowed me to do things that I have put off. I guess that some good has come from it other than to, hopefully, avoid getting sick. Thanks again for the help…Rob


We too are catching up on studio work. My husband has even threatened to clean his bench! I’l believe that when I see it.