Can you cast white metal or low melt solder by pouring it into a simple mould?

[Londontram]

Hi chaps I think I asked this a few years ago but don't think I got an answer or can't remember if I did.

 

 I've picked up over the years the odd unmade or half built kit that was missing the odd part.

 

 So the question is if I make an impression mould of a flat simple part say a smoke box door or something simular in a medium like plastacine could you then pour a small amount of white metal or even low melt solder into the mould and make a casting?

 

  If plastacine wouldn't stand the heat is there anything else like plaster of Paris that would do.

 

I'm looking for a cheap and simple way of making a few odd parts not a large scale production so want something simple I could do at home.

 Thanks Steve

[GeoffAlan]

Dry Sand. Capitals intended.

You can use a fine sand, but if it's damp even a tiny bit, you'll get showered with molten metal. We used to make fishing weights and other bits where a bit of 'grain' on the surface doesn't matter. 

For modelling purposes you'll need something like the stuff the commercial casters use, which is a rubber like material. They use it in a spinning disc to minimise air bubbles. 

[hayfield]

I have made moulds from a product called Siligum from a well known art store

 

https://www.ebay.co.uk/itm/311597267467

 

The mould formed very well, and fine for resin casting, trouble with casting with whitemetal is keeping the whitemetal hot enough not to solidify too quickly, failing to flow into all the crevices. Then you have the shrinkage problem. I guess its fine for smaller parts

Edited April 5, 2020 by hayfield

[knitpick]

Many years ago I did some low melt metal casting using RTV (Room Temperature Vulcanising) Rubber moulds that I created from a plasticard master.  The RTV Rubber wasn't that expensive. 

 

The RTV rubber came from Alex Tiranti (if my memory serves) and the low melt metal was Prince August casting metal for model soldiers.  But then it was quite some time ago . . .

[chris p bacon]

If you're only doing small items I would look at picking up a small resin casting kit,  That might be a lot easier.

 

Like Knitpick I've used some RTV and cast some small items such as chimneys and domes, it was ok but a bit hit/miss as it's difficult to get the temperature of the white metal right. 

 

I made the master in plastic

Then cast them

This was the first cast and from this I learnt all about airways!

 

[RodneyS]

If you are pouring hot white metal into anything that might be a bit damp it could spit back at you.

Commercial casting machines have a lid to catch anything that comes out of the mould.

 

ALWAYS WEAR EYE PROTECTION. 

 

Your skin will heal from a metal burn, your eyes won't.

Rodney

[burgundy]

1 hour ago, chris p bacon said:

If you're only doing small items I would look at picking up a small resin casting kit,  That might be a lot easier.

 

Like Knitpick I've used some RTV and cast some small items such as chimneys and domes, it was ok but a bit hit/miss as it's difficult to get the temperature of the white metal right. 

 

I made the master in plastic

Then cast them

This was the first cast and from this I learnt all about airways!

 

A couple of suggestions prompted by this post.  

A light dusting of talcum powder before setting up the mould will help to keep the mould useable for longer. I think Tiranti also sell graphite powder for the same purpose before first use of a mould. 

The first couple of pours will seldom produce good castings. You need a couple of goes to heat the mould up, as this will mean that the metal will flow more freely and solidify less quickly in the wrong places!   

Best wishes 

Eric 

[chris p bacon]

16 minutes ago, burgundy said:

A couple of suggestions prompted by this post.  

A light dusting of talcum powder before setting up the mould will help to keep the mould useable for longer. I think Tiranti also sell graphite powder for the same purpose before first use of a mould. 

The first couple of pours will seldom produce good castings. You need a couple of goes to heat the mould up, as this will mean that the metal will flow more freely and solidify less quickly in the wrong places!   

Best wishes 

Eric 

Thanks Eric. Yes those are some of the lessons I learned from this, I'm lucky in that I am in contact and meet up with Mike Trice (of the original MJT) and he has given me lots of help and advice over the years.

 

I used talc and managed to get enough usable items out of the moulds for my purposes, I'm currently experimenting with some bogie sides which I'll put on my thread (when I get to it)

 

 

[Fat Controller]

2 hours ago, RodneyS said:

If you are pouring hot white metal into anything that might be a bit damp it could spit back at you.

Commercial casting machines have a lid to catch anything that comes out of the mould.

 

ALWAYS WEAR EYE PROTECTION. 

 

Your skin will heal from a metal burn, your eyes won't.

Rodney

I'll second that; a school friend poured molten lead into a mould that had some residual moisture. The lead 'blew back', causing severe burns (and subsequently scarring); fortunately, his eyes escaped injury. Oddly, he became a technician in the Metallurgy lab of our local steelworks.

[John Harris]

3 hours ago, knitpick said:

Many years ago I did some low melt metal casting using RTV (Room Temperature Vulcanising) Rubber moulds that I created from a plasticard master.  The RTV Rubber wasn't that expensive. 

 

The RTV rubber came from Alex Tiranti (if my memory serves) and the low melt metal was Prince August casting metal for model soldiers.  But then it was quite some time ago . . .

 

Prince August are still around, now based in Ireland.  Now producing mythological figures from Ireland, though sadly short of UK stockists, only W. Hobby.

 

jh

[Devo63]

I have cast a fair amount of metal parts over the years using both RTV and plaster moulds. RTV is great for complex shapes that may require undercuts etc. to the parts whereas plaster is handy for simple pieces. RTV is best if you need a large number of copies of a part. Plaster moulds only give you a few castings before they are no longer any use.   

I make a simple card container (sometimes the bottom of a milk carton will do) and place a layer of plasticine in the base into which I press the master. At this stage I use some scrap plastic or wood to make basic pouring gates. They nearly always need adjustment to get the metal to flow properly but doing it this way cuts down on some of the carving later. 

I pour over the RTV or plaster to make one half of the mould and then allow it to set completely. I have a small hand vacuum pump which I use to suck out air bubbles from the mix before it sets. 

Once set everything is removed from the container and the half completed mould can be placed back in ready for the other half to be poured. Be careful not to dislodge the master when removing the plasticine. I use a simple light oil spray to stop the second half of the mould bonding to the first but there are probably better products around for this. I forgot to do this on one plaster mould and had to chisel out the master and start again when it all bonded together.

RTV moulds can be used almost straight away but I usually give them a clean before I first attempt a pour. The plaster variety need to set very hard and be devoid of moisture before you can cast. I sometimes bake plaster moulds in an old toaster oven at about 80°C to make sure they are thoroughly cured.

I still have a couple of kilograms of casting metal in twelve inch rods that I bought a few years ago from a local war gaming and model supply shop which is sadly no longer in business but I have located another casting supply shop when I eventually need to buy some more. I do most of my casting in the back shed or the carport using a small gas camping stove ring and a small ladle I acquired in the dim, distant past. Also, as recommended above, I have safety goggles and leather gardening gloves for a bit of protection. I dust the inside of the mould with talc and clamp a pair of thin plywood sheets to either side of the mould to provide support and then start casting. It sometimes takes a couple of pours before the mould has heated up sufficiently for even distribution of the metal and you may need to cut more air channels in the mould to get a better flow. Any failures can go back in the ladle.

I have been doing this off and on for the last 30+ years. I have had a fair few failures but these are outweighed by the many successful castings I have made.

One last quick note - there is sometimes a bit of shrinkage to the castings when cooled compared to the original master. This is usually most noticeable on larger parts such as boilers etc. and allowance may need to be made when crafting the master. Some of the modern casting metals don't seem to shrink as much as the older types but it is something to be aware of. 

 

Dave R.      

 

[Londontram]

51 minutes ago, Devo63 said:

I have cast a fair amount of metal parts over the years using both RTV and plaster moulds. RTV is great for complex shapes that may require undercuts etc. to the parts whereas plaster is handy for simple pieces. RTV is best if you need a large number of copies of a part. Plaster moulds only give you a few castings before they are no longer any use.   

I make a simple card container (sometimes the bottom of a milk carton will do) and place a layer of plasticine in the base into which I press the master. At this stage I use some scrap plastic or wood to make basic pouring gates. They nearly always need adjustment to get the metal to flow properly but doing it this way cuts down on some of the carving later. 

I pour over the RTV or plaster to make one half of the mould and then allow it to set completely. I have a small hand vacuum pump which I use to suck out air bubbles from the mix before it sets. 

Once set everything is removed from the container and the half completed mould can be placed back in ready for the other half to be poured. Be careful not to dislodge the master when removing the plasticine. I use a simple light oil spray to stop the second half of the mould bonding to the first but there are probably better products around for this. I forgot to do this on one plaster mould and had to chisel out the master and start again when it all bonded together.

RTV moulds can be used almost straight away but I usually give them a clean before I first attempt a pour. The plaster variety need to set very hard and be devoid of moisture before you can cast. I sometimes bake plaster moulds in an old toaster oven at about 80°C to make sure they are thoroughly cured.

I still have a couple of kilograms of casting metal in twelve inch rods that I bought a few years ago from a local war gaming and model supply shop which is sadly no longer in business but I have located another casting supply shop when I eventually need to buy some more. I do most of my casting in the back shed or the carport using a small gas camping stove ring and a small ladle I acquired in the dim, distant past. Also, as recommended above, I have safety goggles and leather gardening gloves for a bit of protection. I dust the inside of the mould with talc and clamp a pair of thin plywood sheets to either side of the mould to provide support and then start casting. It sometimes takes a couple of pours before the mould has heated up sufficiently for even distribution of the metal and you may need to cut more air channels in the mould to get a better flow. Any failures can go back in the ladle.

I have been doing this off and on for the last 30+ years. I have had a fair few failures but these are outweighed by the many successful castings I have made.

One last quick note - there is sometimes a bit of shrinkage to the castings when cooled compared to the original master. This is usually most noticeable on larger parts such as boilers etc. and allowance may need to be made when crafting the master. Some of the modern casting metals don't seem to shrink as much as the older types but it is something to be aware of. 

 

Dave R.      

 

Thank you Devo and all of you. Your answers have been extremely usefull and as its for on off items and not a production line I'm very tempted to have a go wth the plaster mould method. 

 

 One final question over the years I've picked up all sorts of abbandend kits and if not complete enough to build have stripped them of useable parts like chimneys and domes and other such parts which has left me with a box of mis shapen bits of white metal would these be usable for casting with?

[t-b-g]

Several years ago Ken Hill and I had a go at casting metal using a beginner's  kit from Citadel Miniatures which we found in the "Hobbies" catalogue.  We made some chimneys, domes and canopy support pillars.

 

It came with metal plus two part mould making solution.

 

Most satisfying and enjoyable.

[chris p bacon]

1 hour ago, Londontram said:

which has left me with a box of mis shapen bits of white metal would these be usable for casting with?

I've used them, it's where my material came from. You do have to keep an eye on impurities in the metal though. 

[5&9Models]

I sometimes have spare capacity in my moulds so if you ever want to send masters to me, I’ll happily find a space and cast up what you require.

(5&9Models)

[Londontram]

44 minutes ago, 5&9Models said:

I sometimes have spare capacity in my moulds so if you ever want to send masters to me, I’ll happily find a space and cast up what you require.

(5&9Models)

Thank you for the offer but after reading the responses on this thread I rather fancy a go now.

[5&9Models]

54 minutes ago, Londontram said:

Thank you for the offer but after reading the responses on this thread I rather fancy a go now.

Go for it, it’s a very satisfying process.

 

On a more general note, if anyone on RMweb has a master for parts they need casting I’m always willing to help out. I don’t need to make a living from it as it’s only a hobby, so apart from the postage the costs are tiny. Always worth asking?

[Devo63]

Reading back through my previous post I noticed that I had neglected to mention a very important step when pouring the first half of the mould. Before pouring the RTV or plaster you should make 3 or 4 indents in the plasticine with a rod to make registration points for when the two halves of the mould are joined for casting. If this is not done it is fairly easy ceate a misalignment which leads to mis-shapened castings.

 

Dave R.