No it is not a general warning it's highly likely possibility. If you want my cv I have been involved with precious metals since I was 14 yr old,plenty of casting experience from bars to jewellery, lost wax, kiln firing, mold making and home refining and pouring. I my experience I have seen what you are showing in lost wax castings and bars, due to the mold not being dry, and also from over heating, mostly from moisture. I would be seriously looking at your casting environment, eg cold area and hot metal pours create moisture and gas explosions from this are a hazard, bake your molds 150- 200c in a kiln or oven for a couple of hours before pours, zip locks won't work, plastic bag molecular structure is not resistant to atmospheric water/ humidity working in the temp range you are working. Just how hot are you getting your metal before pouring, as in temp, I would not recommend above, 1100c for sterling, you alloy composition should not matter to the extent that your issue exists. You must note all changes in your procedure and note the effect of those changes, you must strive for consistency. There are a few of your pours that look fine, you must note whatever change. I will pm when o get home from work and give you some reference books to chase up at a library or online, these are crucial for your future if you want to do this correctly and teach a lot about method, alloy temps etc for casting, lost wax etc. you do not mention your type of mold? Carbon graphite/ silica/ home made or cast iron?
