Casting with Zinc (a review)

[Evil Dog]

Will be laying in a supply of zinc tomorrow, so I guess I'd best go over the basics just to see if I am leaving out anything real important.  This is #3 Zinc Alloy (97% zinc) in 22 pound ingots.  My current plan is to place an ingot atop my RCBS bottom pour melting pot.  Will melt it into the pot with either a propane torch or my oxy-acetylene setup.  Since zinc is supposed to melt at 781 degrees F I will set the RCBS pot at 825 to 850 degrees.  Will flux with beeswax and spoon off the trash.

For actual pouring, I plan to transfer sufficient zinc from the RCBS pot to a large steel ladle.  The ladle will be placed on a heavy duty propane burner just to keep the zinc up to temp between pours.  The main reason for the ladle is that it will pour the required quantity of zinc a lot faster than the bottom pour pot.

Will wait 2 minutes by a clock for the zinc to solidify before opening the mold.  The mold itself is machined steel, 3" diameter by just under 4" long, held closed with "c-clamp" vise grips.

Naturally the usual safety precautions will be observed.... heavy gloves, jacket, face protection, working in a well ventilated area.

Am I forgetting anything that might get me in trouble?

[CAV Trooper]

My current plan is to place an ingot atop my RCBS bottom pour melting pot. Will melt it into the pot with either a propane torch or my oxy-acetylene setup.

EvilDog,

Will your melting pot hold all 22 pounds of zinc at one time? If not, it might be a better idea to cut the ingot into chunks that will fit and let the pot melt it.

I'm picturing an ingot sitting on top of the pot and the torch being used to melt the zinc into the pot sort of the way an ice cube melts. If that works, everything is great, BUT...what would happen if the whole ingot got to 781F and decided to liquify all at once? Could be an extremely dangerous mess.

Having worked in a foundry many years ago, I have a real healthy respect for molten metal. My wife made me quit after about a week because I came home one day and she saw my name tag had melted off of my hard hat.

[Cat Whisperer]

A very LITTLE zinc will contaminate the pot for casting lead alloy!  Save the RCBS bottom pour and use an iron pot on top of  a turkey/fish frying propane burner.

[GGaskill]

I would stay away from playing a direct flame on the zinc as that is likely to oxidize it much faster than just melting it would.  Remember the MSDS for zinc oxide fumes (metal fume fever.)  No reason to produce them when it is not really necessary.

[Will Bison]

Don't use any of your regular casting gear for melting the zinc. I destroyed a good pot that way in 1964 when I was learning how to cast zinc. Also the typical electric lead pot won't achieve the temperature required.

Use a turkey fryer as CW suggested along with an old cast iron or stainless steel pot. No aluminium!!!!

All the rules for lead casting apply, double.

Zinc will require quite a bit of temperature, I bring it up to a very dull red as viewed in a dark place. I don't have a thermometer but I'm guessing around a 1,000 degrees.

Last but not least Ventilation, Ventilation, Ventilation.

[Evil Dog]

Ok, you talked me into it.... will save the RCBS pot for centerfire stuff.  Will just check for old cast iron pots at the local swap or garage sale.

[GGaskill]

Assuming "Zinc #3" means Zamac #3 Zinc, the melting temperature is only (only) 728° F.  See this Purity Casting Alloys Ltd. web page, the next to the last section.

[Evil Dog]

My limited understanding has #3 Alloy Zinc at 97% zinc and 3% other stuff.  That Zanmac does sound pretty close though.  As to melting at 728 or 781..... am I really likely to notice the difference?  Not likely.

[Third_Rail]

If you get it too hot (hot enough to vaporize some of it) you'll notice.

I don't know how you have the guts to cast zinc.