Tin, casting?

[chunkolini]

A weird one again.
I have been asked to make a 10th annjversary gift for the cast of a TV show, at present a very vague brief, but they want it incorporating Tin as this is the metal for a 10th anniversary. No I didn't know that either.

Anybody got a clue as to where I can source some, I figure decorative trim using it, so probably in thin sheet, bar or strip form. Many thanks.

Chunko'.

 

[rtbcomp]

What you need is a tin suppliers guide, Ah! here's one

This might be better for the UK http://www.kompass.co.uk/directory/products/item/0/uk/Brass,_tin/3431026.htm

 

[chunkolini]

More information now.
They want 3d life sized models of the heads of some of the cast. A bit out of my field. But...
I have a friend who can make casts of the the faces to use as basis for moulds, is their any mileage in trying foundries, is Tin a metal that can be cast? I am sure this is a specialised job but I cant see why I cant front the job and contract bits of it out.
I will probably turn them down but I should do my research first.

Any info gratefuly recieved.

Chunko'.

 

[rtbcomp]

Tin can be cast, why not use lead-free solder? they don't need to know.

I think modern pewter is virtually all tin

 

[Robotstar5]

My great great grandfather was a tin miner, unfortunately the skills have not been passed down so I can't help!

 

[madkayaker]

its nasty stuff to cast apparanty as it has a habit of going spit really easily from what i remember from watching a program on white metal lining bearing housings you have to heat the tools and moulds etc before adding the metal

 

[peteypt]

I've cast pewter (well, copious amounts of lead free solder) into plaster moulds.

Are you any good at engraving / modelling etc? could you not make a positive of the heads from wood / plastic (see ebay for mouldable plastic - very good) clay / plasticine etc then make a mold (negative) of these, and cast the 'tin' into them

I melt tin (pewtor) in a stainless cup over the gas hob and pour it in to mould, tap it about to remove air etc etc etc then remove from mold. (Use release agent if want to reuse the mould)

Then work some chunko' arty magic around the castings lol?!

 

[peteypt]

its nasty stuff to cast apparanty as it has a habit of going spit really easily from what i remember from watching a program on white metal lining bearing housings you have to heat the tools and moulds etc before adding the metal

Yep...but keep everything nice and hot and play a flame around the mold / molten metal and it's doable

 

[peteypt]

tin content -

Tin can be cast, why not use lead-free solder? they don't need to know.

I think modern pewter is virtually all tin

Just gone out to check my lead free solder composition ;

Metal content is 99.3% Tin - 0.7% Copper - Flux free

I don't think they'd notice..

 

[Shox Dr]

And how much lead free solder would you need to make a bust? I think I'd be looking for cheaper sources of Tin

 

[peteypt]

And how much lead free solder would you need to make a bust? I think I'd be looking for cheaper sources of Tin

Depends how big - I'm imagining a gift to be something fairly small.

In my mind I can heads about an inch in diameter and fairly flat on an elaborate backing piece.

Obviously it will depend how big, but can get more than enough solder off the bay for 15 quid if only a few small heads need casting.

But that said, I've seen Chunko's work, and he likes BIG lol.

 

[mike os]

Pewter mate....

 

[TechnicAl]

Gunmetal could be another possibility but its not Tin colour
http://en.wikipedia.org/wiki/Gunmetal

I think Pewter is the favourite
http://en.wikipedia.org/wiki/Pewter

 

[peteypt]

As a thought for getting hold of cheap pewter - how about broken tankards / ornaments and the like? Cheap off Ebay, cheaper from your local engraving shop (according to a friend they mess up too ) and probably cheaper still from carboots?

Think Pewter has a melting point somewhere in the region of 220° to 240° depending on what's in it. So that's definately doable for a bit of DIY casting

 

[astro_al]

Why not just get it cast in steel and then fart about with some tin around the edges or whatever.

Al.

 

[pidgeon chit welder]

You could make it hollow in two halves using the lost wax casting method and fine flame solder braze it up along the front and rear seam,then polish it out .....like a home made easter egg


Perhaps make a latex mould of their faces ( straws up their noses for breathing and vasaline on their skin to release it all , once set remove it & make a plaster support . fill the mould with warm liquid wax , pour out the remaing wax once the first 1/2 inch has set so you get the thickness of the metal to be cast , then let it cool in airing cupboard type temps so it does not shrink and crack because of cooling too quick ( read up casting bees wax )
Do not bung it in the fridge or freezer to get it to set it will almost certainly crack .

If you get to this stage gently remove the wax master add a decent filling sprue or two c/w a decent liquid metal reservior and add some vent sprues .

Now dip cast it in clay slip or poured plaster of Paris ..Id be tempted to spray or dust something ( trial and error ) on the wax to get the plaster of P or slip to stick . De aireate the casting medium as best as possible before pouring ( a decent vacuum chamber is of immense help once poured over the wax form )

If you go this route look up centriflugal casting for you will need something to fling the molten metal right through the hollow mould once you have heated up the mould to get the wax out .

 

[chunkolini]

pigeonchit
That is a very fine description of the lost wax casting method.
Something that is on my list of skills to try along the line.
For this job, assuming they decide to go ahead I would look at getting it done by a foundry, I have a mate who makes theatre props so I would leave the making of the initial moulds up to her.

Chunko'.

 

[TechnicAl]

I used to work in a Foundry making Steel castings. We used the lost wax process to make golf clubs. We also used centrifugal methods to produce aero engine parts, mainly casings.
Be very carefu, both processes are very dangerous. If youre going to use a Tin alloy it wont be so bad because the temperatures are lower. Remember that pouring molten metal onto a damp mould will generate steam and the volume difference is staggering. Its enough to cause an explosion like reaction and spew the molten metal back out of the mould.
We used to spin at 3000 revs so you can imagine the inherent danger in that. Just think of your spin dryer full of molten metal.
We also used polystyrene as a mould. The molten metal would volatalise it. Similar to the LW but less accurate.

All Im saying is be careful

PCW.....we never used Plaster of Paris. Do you think it will stand the heat?

 

[rtbcomp]

I've a feeling pewter represents an anniversary in its own right, but I can't find a reference on Google.

You could try hollow casting, the way they make handles for tankards.

What you do is pour the molten metal into the mould, wait a second and then pour it out again. What happens is that the metal sets where it contacts the mould and the still molten excess from the centre is poured out.

For pewter tankard handles they use a two-part steel mould, but a sacrificial plaster of Paris mould might be OK. P of P does change it's composition with heat, but I think that happens at about 1000 degC.

 

[mike os]

why bother with PP... get some proper investment material