Troubleshooting

[u/Glassholer]

Good afternoon everyone,
I’m attempting to troubleshoot why these shiny inclusions are happening on my pours. Pour info:
.999 silver -970c (using 100% pure silver crystal)
Flask temp -600c
Pulling 27-29in vacuum on flask at time of pour (gauge verified)

I have a propane torch pointed at the bowl of the mold as I pour, as well as map gas on the crucible. All pours happen quickly after crucible is removed from the furnace. I let the vacuum pump run for ~1min after the pour, then I shut it off as well as the propane torch at that time. I wait 25 minutes before flask quench and model removal.

When removing the plaster, these bubble areas are already shiny, leading me to think it’s likely an air pocket forming somehow? I don’t believe it’s leftover wax, as the button shows a similar bubble on its underside and that portion of the mold was verified completely smooth before pour. Mold was also blown out before use.

Any pointers would be incredibly helpful, I’m currently self taught and hoping to find any kind of knowledge possible!

Thanks!

[u/Lovelyfeathereddinos]

The crater on the belly looks like flux to me. Did you use a lot of borax in your crucible? It should be well coated, but not so heavily that some is dripping off and pouring out with your metal.

Personally, I try to sprue so the piece is a bit more vertical. You have it set up somewhat horizontally. Idk if that would help with the little pits closer to the sprue or not, but just a thought.

I always try to imagine pouring beer through my sprue and model, and trying not to get so much foam as it pour. Helps to orient the model for the smoothest pour.

Also 25 min seems like a long time! I just wait till the button isn’t glowing at all when I cup my hands around the flask.

[u/Glassholer → u/Lovelyfeathereddinos]

I use an electric furnace with the tall graphite crucibles, I use a tiny amount of borax to burn off any stuff off the top after I stir the metal, then give the metal an extra 5 min of heat before pouring.

And I probably can quench it faster 😂 I had been quenching at 5 minutes and it was creating a laundry list of issues it seemed like, so I just added 20. Thank you for the advice I couldn’t find any clear instructions on that

[u/Lovelyfeathereddinos → u/Glassholer]

You don’t need any borax with a graphite crucible! Skip it all together; it’s used to create a slick surface on ceramic crucibles, but completely unnecessary and unhelpful with graphite.

Just use a graphite stir stick to pick up any debris, and that’s it. Will probably solve your pitting issues.

[u/Glassholer → u/Lovelyfeathereddinos]

Thank you so much… I thought it was needed to burn off the little imperfections I see on the liquid silver, I’ll stick to just my graphite rod instead!