Low melting point casting

Here we look at casting with low melting point metals such as peweter and lead. These are safer than other metals, due to the lower tempratures, whilst the principles are the same.
This is still dangerous and we take no responcibility for anything resulting from the information on this site or the accuracy of any of the information.

Equipment :-

Low melt point metal

To start with it's good to use a low melting point metal. Lead is easy to work with BUT bear in mind that lead is poisonous the fumes are particularly bad for you. A beter bet is to get some lead free pewter (see suppliers) which is just as easy to work with and not so harmful.

Plaster of paris / Moulding plaster

Bag of Plaster Used to make a mold. Plaster used to fix a hole in the wall will be OK (polyfiller etc.) I use modeling plaster which is a very fine grade mainly because I have it around for other projects. A cuttle fish from your local pet shop (used for birds to chew on, NOT a live fish!) can be used to make the mold from if it's easier for you. A number of other substances can also be used but best start with what you know before you experment.

Ladle

An old ladle or long handled spoon type thing, anything made of steel / iron etc that looks like a big spoon BUT it must have a long handle or you'll burn yourself! It may well be 'damaged' in the process so don't use the spouse's best tableware.

Heat source

The heat source can be a bonfire, barbeque, even an old stove will do. Make sure that whatever you use it is used outside and isn't wanted for dinner later! You also require a means of securing the ladle over it as it may take longer to melt the metal than you can hold the ladle steady in your hand.

Method :-

Make a mould

The mould can be a carving made in a cuttle fish which is the fastest method of making a mould.
If using palster, mix up the plaster and leave it in a pot of some kind (bottom of a plastic milk bottle, yougart pot etc.) and leave it to dry. Plaster MUST be VERY dry before use for metal casting! A couple of days drying should do it or a few hours in the oven at a temprature over 100c if it is in a container that can take this temprature. If it's in a plastic pot, wait till it's set, remove it from it's pot then put just the plaster in the oven.

Now into the plaster carve your design using a knife, chisel, old screwdriver or any impliment that you wish. Bear in mind that your making a negative! You will be filling the mould with the metal so if you want half a sphere to be cast, scoop out a dip in the mould material.

Plaster in a pot Plaster carved into a mould
Plaster Setting in a pot Set Plaster after carving is done

Once the master mould is made place it on a pile of earth or sand or something near the fire. The earth / sand will support the mould AND if you spill the moulten metal the earth / sand should contain it. Don't pour moulten metal where an error could result it the metal going onto something that could catch fire or where it could run off downhill towards you or something that could be damaged.

Melt the metal

Place the metal in the ladle (make sure you don't over fill the ladle! Half full is about as much as is safe. Place the loaded ladle over the fire and leave it there till the metal melts. Peweter, lead, and most 'white' metals will melt this way quite easily.

Starting a melt Metal softening Moultern metal
Starting a melt Metal softening Moultern metal

Pour the metal into the mould

Before starting to pour your metal ensure that you have a safe place to put the ladle and it's remaining contents. When the metal is fully moltern carefully pour it into your mould. Set the ladle down somplace safe leaving any excess metal in it. when the metal cools it may easily come out or it may not depending on the exact composition of your ladle. If it comes out as a sort of ingot all well and good, if not you can add a little more to it and use it on your next casting of the same type of metal.

Take the object from the mould

Wait for everything to cool down and you're all done!
This could take anything from 10 miniutes to several days depending on the size of the casting. Best to be safe than sorry and leave it longer than you think it needs. Extracting the casting from the mould only to throw it across the room and set fire to the dog with it because it was too hot to handle will ruin your casting, require the dog to have emergency treatment, your wife to beat you with a rolling pin for being so silly and eventualy you to go to A+E for the 1st degree burns on you hand. Best wait a while I think.

Cooling in the mould Moulded item
Cooling in the mould Moulded item

Conclusion

You are now a founder!
This should show that foundry work can be quite simple.
You may notice that most of the time was spent making the mould. If you didn't really take your time on the mould (I did the one above in a very short time) then the results aren't that good. Like many things in life preperation is the key to good results. Pattern and mould making is the true key to good results and most books on foundry work concentrate a large percentage of their words on the subject. Once you have a mould all you do is melt some metal and pour it in.