The science behind pouring shots or flakes?

[autumnwillow]

I understand that the water should be cold enough so that when the metal being poured is cooled before it makes any contact with the tank.

Producing shots would require a second crucible with an orifice that is heated while pouring the metal into it.
Producing flakes would be as simple as pouring the metal into the water. Better if you are pouring in a circular motion rather than a one straight pour.

Is a stainless tank really required? Can I use aluminum or cast iron? Thick stainless tanks are expensive! I need to pour about 500gms to 2kgs of shots.

What causes the metal to explode when poured? This happened to me and it happened when I saw one of the beads glowing red, the water was hot, but not that hot, I could still touch it. I was also pouring by batches as my current "tank" is only about 6" deep.

I know that using ice would help but how about the distance from the tank and the pour?
Does air also take part?
Moving it to a higher distance would make the metal fall faster but it would also help the metal to be cooled by air.

Keita.

 

[nickvc]

It's all a little trial and error with making shot, we used to pour from the crucible onto a vee shaped piece of stainless sheet immersed in the water which went direct into a metre high cold water container with a tap on the bottom, others advise using the drilled heated crucible and moving water in your tank you pour into, if the shot is for yourself I wouldn't worry too much so long as the alloy is good.
You can pour into even deep plastic buckets with a stainless plate in the bottom so long as you do not pour too much or too fast.
The explosions are usually caused by trapping water inside the metal which then boils and cause the shot to explode, we had more problems with silver than gold.

 

[4metals]

It all depends on why you are making shot. Shot made to aid in digestion is simply made by pouring slowly from a standard crucible into water, pour slowly. You can make the shot even smaller by placing a hardwood board in the water at an angle and pouring the molten metal so it strikes the board just at the water line.

Shot for sale to jewelers is usually much nicer, round and more uniform.


This is usually poured through what is called a shot box. A shot box is nothing more than a graphite block or a crucible with small holes drilled in it. I prefer 1/8" or smaller. The crucible is placed in a holder like the one shown below. It is made so the bottom of the crucible is about 1/2" above the water line. This is the shot box (crucible) preheated and placed in the holder before the gold is poured.


I like to pre heat the shot box by putting it right on top of the gold while it is melting.


When the crucible is glowing and the gold is molten it is ready to be placed in the holder and the gold poured. The action of taking the shot box out of the melting crucible and getting it in position and the pouring needs to be done as quickly as possible to avoid the gold cooling off and not passing through the drilled holes.


This is what the gold looks like as it comes out of the drilled shotting crucible into the tank below.


The tank does not necessarily have to be stainless steel. I have seen plastic drums with a large stainless steel funnel to direct the shot into a small stainless bucket placed below it in the drum of water.


I prefer stainless because after going through all of the effort to make fine gold, I prefer not to risk contamination.

Metal can explode when you pour it too quickly and form steam which overheats the quantity of water you are pouring into. This is more prevalent when pouring into small quantities of water.

For producing fine shot a 6" deep tank is simply not deep enough. Unless you are doing very few ounces. In the setup shown above fine gold in quantities up to 600 ounces are poured routinely with good results. It will also work for melts around 1 kilo, but much less gold would require a different approach.

 

[autumnwillow]

Very nice setup 4metals. I'll do that once I get to 600 ounces. Right now I'm just at the 2kg limit.

For now I just bought an aluminum stock pot - not to be confused with the common stock pot here, its a stock pot for cooking. It's about 12-14" in height, and 10" in diameter. I'll give it a try tomorrow with ice in the water and see how it would go.

 

[nickvc]

I'd advise adding some stainless plate cut to fit the bottom, as I said you can pour into a large plastic drum so long as you put a stainless bottom into it, surely you can buy an old pot or a pieces of stainless sheet and get it I fit the bottom.
I'd be worried pouring into aluminium as it's melting point is low if the gold is still hot when it hits the bottom you could have a mess to sort out!

 

[autumnwillow]

The aluminum stock pot worked fine. I still had a one small explosion though. Water was cold when I touched it.
This happened on inquarted gold. 200g first, then i left the 200g shots in the pot, melted another 450g, then poured in 4 batches, it happened on the 3rd batch.
And there was ice in the pot!

I wonder why these explosions happen?

I think I may have been going too fast. I'll try again tomorrow.

 

[grainsofgold]

4 metals-

I see where you have shown the shot box being heated- once removed it takes time to set it up in the shot box holder above the water line-

What is the approximate time window you have to set up the shot box in the holder and pout once its off the heat source ?

I have seen some set ups where there is a torch flame applied to the shot box once its set up to aid in keeping it hot-

Moving hot flasks around and getting them set up properly seems to me where accidents can happen and Im all for thinking it through and even doing dry runs in order to make the process safer-

thanks for posting on this

 

[4metals]

The fixture that holds the crucible or shot box is made to set the bottom of the shotting box about 1/2" above the water and there are usually bolts that can be adjusted for a new crucible. What is usually done is the cold shot box or drilled shotting crucible is placed in the fixture and the water level adjusted so everything is right.

Then the shotting crucible is removed and placed in the melt furnace to heat it up. It only takes a few seconds to put the shotting crucible in place once it is heated and turn around and grab the molten metal to pour it through the shotting crucible. I would guess the entire time frame is 15 seconds between starting to place the shotting crucible and actually beginning the pour of the molten metal.

Some guys do like to keep a flame on the shotting crucible to maintain heat but that is for larger pours or silver where you want to burn up the oxygen with a flame over the shotting crucible.