Yes, and if you want the best quality you should scalp (remove) the outer surface to get rid of any metal/mold reaction products.
Do you use a steel mould?
I used Delft clay because it was just easier to reset the mould in
case of operator errors.
When I picked up a copy of Mark Grimwade’s book “Introduction to
Precious Metals”, it confirmed that it’s a good idea to use sand or
clay for making ingots… well if you’re interested in an even grain
structure throughout the ingot. So of course I use it all the time
to make ingots.
I was wondering if the use of steel moulds today is due to the
expense of the clay or because “it’s always been done that way”.
Regards Charles A.
P.S. Just traded away some of my ingot moulds, and gave away a few
to people in need.