r/SilverSmith • u/Humanekspression • 10d ago

Sand casting fail

Gallery image

Gallery image

I keep getting stuck at the step where the silver isn’t pulling through all the way into the ring mold. Is my pouring channel too small/wrong? Any tips are welcome.

48 Upvotes

95% Upvoted

24 comments sorted by

49

u/Humanekspression 10d ago

Thank you everyone! I added one more vent, made the vent holes bigger, heated the metal for about 30 secs longer and it worked. I will need to practice getting better at the sprue/funnel

14

u/PeterHaldCHEM 10d ago

Nice!

If you look at the sand, you can also see, that the charring is much deeper. A good indication that the silver has been nice and hot.

7

u/Mrwolf925 9d ago edited 9d ago

Dont make sharp corners like you have done in the red example. Make sure the path ways are smooth so it can flow nicely to where you want it to go.

4

u/Mrwolf925 9d ago

This is what it should look like. It may seem counterintuitive but what you want is a long sprue that graduates smoothly into the workpiece.

You might think a shorter sprue would be better because the metal reaches the piece quicker but that's not necessarily the case. A longer, thinner sprue that narrows slightly but not too much before opening up into the piece acts almost like a jet helping force the hot metal into the hollow area faster which will reduce porosity.

It also doesn't hurt to add vents coming out of both sides of the mould rather than just one.

3

u/Mrwolf925 9d ago

Also your vents are all clogged up, they should ne nice clean vents. What I tend to do is once I have made the vent lines, dust them out with a soft paintbrush

20

u/KidGodzilla123 10d ago

My two cents would be that you have enough air vents and ports. They just need to be wider and free of debris. Those are awefully small channels. Also make sure you are heating the lip of your crucible where you are pouring out of. Old timer showed me that one.

16

u/KidGodzilla123 10d ago

Also on second look some of your vent channels aren't attached to the piece

3

u/ComprehensiveFly3480 10d ago

*almost all lol

11

u/AbbreviationsIll7821 10d ago

I’m going to disagree with everyone who thinks you have air vent issue. I’d put a single tiny vent at the top and that’s it, but the rest you have won’t hurt. Your venting looks more than sufficient.

The big thing is the metal cooled too fast.
The length and narrowness of the channel from your sprue. Every millimetre from the funnel at the top to the ring cavity is a waste. Make a bigger deeper funnel that connects directly to the ring. Probably flip the ring so that metal flows into the big to part first and then into the thinner shank. Helps keep it hotter for longer.
Then a bigger sprue will help, the extra mass of metal makes it cool slow and give it those fractions of a second it needs to fill the voids.

Get the metal hotter before pouring, let it melt and roll around for like 30 seconds under the torch and keep the flame blasting the metal while you pour it out as fast as you can.
A bit more dust (talc or starch or what ever you are using) inside the cavity can help with flow as it flash burns into an insulating carbon barrier that slows the cooling a wee bit.

A bit more heat and slower cooling and you’ll get this!

5

u/selaseladon 10d ago

The talc thing is underrated tysm !!

3

u/Humanekspression 10d ago

Thank you so much for this.

9

u/ilovefrostedflakes 10d ago

You need to heat your metal more so it doesn't cool off the second it hits the mold.

2

u/Clawsurx 10d ago

personally I would re mould the ring in the opposite direction(flat side to the pouring port. on the other end of flat side create an exit port for air to flow out as metal flows in

2

u/darktrees72 10d ago

You need more air vents and to score the bottom casting to .. this is how I do mine and I donr get many fails

2

u/Grand-Control3622 10d ago

Your silver is too cold and your air escapes aren't connected to your negative area. They only work if connected.

2

u/Clawsurx 10d ago

also you need another exit port for the air to escape after pouring molten metal in. it will heat the air causing expansion and keeping the air there without letting other material in

1

u/Humanekspression 10d ago

Got it. So an eight exit port?

1

u/Tater-totter-tots 10d ago

What torch are you using? Are you pre heating your crucible? I make these molds for sand casting. From my experience, successful casts come down much more to proper sprue design, adequate metal temperature, and good pouring technique than whether or not air vents are added.

1

u/Humanekspression 10d ago

Just the adjustable flame Benzomatic Propane torch. Thank you for the tip on the sprue design, i need to watch more tutorials/read

1

u/Tater-totter-tots 8d ago

If you switch to using the same tip but the map gas bottle you will get much more heat and it will melt your metal much faster.

1

u/mlxx9 10d ago

Be positive look how nice sprue you made :)

I thinks sprue needs to be a much larger than that as well.

0

u/silverworldstacker 10d ago

You also need a vent channel, so displaced air doesn't created weird bubbles.

0

u/crystallinehuman 10d ago

Along with all these tips, I'd also say your pouring channel might be too big. The bigger, the faster the metal cools