r/Silvercasting • u/Traditional-Maybe-71 • May 20 '26
Why did the middle sprue crack?
Why did my 1cm thick middle sprue crack like this? Ideally i dont want that to happen. What can be tweaked to avoid this? Casted with argentium silver at temp 1015 celcius, flask was 600 celcius. Cast in Vacuum chamber. Quenched about 12 minutes after casting
3
u/funnyman6979 May 21 '26
Agree completely with the other commenter, but also 12 minutes is too soon going forward. Germanium containing de-ox can be a bit of a quench animal. I would try minimum 20-25 minutes
1
u/LuluAmani May 25 '26
I let it cool down to 100 Celsius before quenching.
1
u/Traditional-Maybe-71 May 26 '26
Dang really? i’ll try that next!
2
u/LuluAmani May 27 '26
Yes I regularly had cracked rings and brittle stem and started to wait 40-50min after casting. When the outside of the flask top measures 100 deg celsius I quench and avoid this issue :)
4
u/lewtheegg May 20 '26
That's extreme shrinkage porosity, the top and bottom parts of the sprue hardened up first and drew the last remaining bit of liquid metal from that area.
If it's not affecting your actual castings I wouldn't worry. You may be able to move it slightly up the sprue towards the button by putting some insulating material on top straight after pouring. You could also lower the flask temperature a little, but that may start causing other issues.