Introduction: Cast Tin!

Picture of Cast Tin!

 I got an order for some tin cubes. I found that there wasn't an instructable for casting tin, so I recorded my steps and went through it for you all to see. 

Why tin? Tin melts very low in temperature. Basically, the lowest melting point of any useful, non-toxic metal(*). It melts around 500 degrees, is very castable, and looks brilliant. There's only one real good reason not to use it: it's relatively expensive. I got mine from Rotometals in San Leandro for around $10/lb. Its density is similar to lead. 




(*) Tin may cause some illnesses, this is debated. work it as if it does. Do your own research. 

Step 1: Safety!

Picture of Safety!

 Molten metal can f- you up.  Cover yourself compleatly. Liquid metal likes to "jump" when it cools. Think of how fryer oil works, except replace "ouch" burns with "I hope you get to the hospital before you die of shock."

Long story: 

 Tin is cooler than basically any other metal you'll ever work with, that means that if you screw up, you'll probably survive and have to deal with the hospital, burn wards, grievous scars, and potentially being disfigured or crippled for the rest of your life. Always have full face protection, arm and body protection that buttons at the neck, and closed toe shoes. 

Respirator might not be a bad idea either, as who knows what those stray 1 or 2 percent are in the 98-99% pure Tin. I suggest doing things outside. 

Pretty much, dress like you're welding, only with a clear visor. Check out my fashion statement picture for an idea. Do any of this at your own risk, perform your own safety assessments. Only you are responsible for the consequences of your actions. 

Step 2: Mold

Picture of Mold

 Make yourself a mold. 

I had a bunch of gypsum cement hanging around, so I made my molds out of it. It was a horrific and almost dangerous failure. Don't do it. 

So after that, I got myself some steel. In this case, obtanium resulted in some 1/4" wall that fit my needs. After dialing the tig welder up to its maximum (and finding out that its cooling fan has 3 levels!), I had a mold. 

The downside of a steel mold is that the steel holds heat so much longer than the tin, so it takes so much longer to cool. casting sands are a good option too, if you can get some. 


Step 3: Melt That Tin: Get Ready

Picture of Melt That Tin: Get Ready

 For a "crucible", I picked up a used stainless steel pan from Urban Ore for 71 cents. It was made of very thick stainless steel, so I specifically chose it over Cast Iron, which is what is normally recommended. If you've got time and the money, get yourself a small crucible, and don't mess around with this stuff. 

For a "furnace", I used an old campstove I found hanging around. It was propane fired, and I've got propane around. I'd suggest doing this in a place with adequate ventilation. Outside worked for me, but I still threw on the respirator, just because it is fun. 

For temperature control, I used a Fluke IR thermometer, which was reasonably accurate, even with the shiny surface of the tin. I also took a lot of readings of temperatures of the pot and the mold to make sure the pot wouldn't melt and that the mold was appropriately hot. 

At this point, don your safety gear, just because. Fire up the stove, throw a blingot into the crucible, and let it heat up over a low-to-medium heat. It'll start to puddle shortly. Once it puddles, you can dial up the heat, and add more tin. It's a lot like melting snow for water, if you've ever been snow camping. 


Step 4: Melt That Tin, for Real!

Picture of Melt That Tin, for Real!

 Well, you should have a puddle at this point, add more metal until you've added the desired amount...


I should say, before you start, it's good to figure out by displacement the volume of metal you will need, then calculate the weight, and add by weight. Tin slumps a lot, because it shrinks when it cools, a considerable amount. Heating your mold and planning for this make this not a problem. 

Tin conducts heat really well, so it melts pretty much only after the whole chunk is just barely below melting temperature... That probably doesn't make much sense on its own, but you'll notice how it doesn't melt, doesn't melt, then just slumps and goes liquid really quickly. 

Step 5: Melt It and Skim It

Picture of Melt It and Skim It

 I'm short good pictures for this step, because it is hard to photograph. Instead, I give you a blurry shot of Milo, looking cute on our shop's couch. Notice our SUPER HANDY table of decimal inches to metrics to fractionals. Every shop should have two of these. 

What you want is for all of the metal to be fluid, no lumpy bits, so get yourself a tool for messing with the molten metal. I used a bent stainless steel spoon.  With a MIG-Welding glove gloved hand, carefully stir the metal and feel for any chunks. Also, be aware of the crap on top.

Skimming the crap: 
 Your spoon is "cold". It's hot enough to burn you, but it is still cold enough to instantly solidify the liquid metal it contacts. We'll use this to our advantage to grab up some of the blackish-yellowish scum floating on the top by grabbing some of the metal under it as well. Feel free to try and stir all the scum to one spot, then pull the spoon out, let it cool, then fish out the scum. It'll take some practice, so be patient, don't let the metal get too hot, and BE CAREFUL, and don't put your face over the molten metal. 


Step 6: Pour and Let Cool.

Picture of Pour and Let Cool.

 So before you pour, make super-sure you got your safety gear on right. It can splatter like hell. Get the layers of your protection right, Get ready, then when you are ready, take a few deep breaths, grab the crucible, and pour slowly and steadily.

If your mold is good, it should be like pouring liquor.  If your mold has any moisture in it, or anything that changes phase below the melting point of tin, get ready for some flying molten metal. 


Then, let it cool, let it cool a lot. 

So before you think you're clever, the Tin conducts heat well, so you can check the temperature of the tin, and get a good idea, right? Wrong. Your mold material doesn't conduct heat very well at all, so it will be smouldering hot for a very long time. Let it sit a while. 

Step 7: Extract, Finish!

Picture of Extract, Finish!

 Either extract or destroy your mold, once everything is cooled off sufficiently, then finish the surface. You outta know that tin shrinks a reasonable amount as it cools, so you'll get some slump in the middle, where the center cooled slower. This sucks. Deal. 

I was doing a very simple casting (a block), so I didn't need any fancy finishing or anything, but at this point, feel free to polish or paint the surface. Go crazy, you've made something of metal! 

Comments

Marinesurfer313 (author)2015-12-01

Soo. Ive made several knives, swords, hatchets, machetes, etc. ftom railroad spikes, leaf springs, Rebar, plate steel.
well now im gonna try to make a soild metal mjölnir (thors hammer ). I'm thinking tin due to it color, low melting point, and weight. I want a heavy rustic looking hammer. I was thinking of aluminum at first, but its too light. And a fuss to get it the right color. So tin it is, or maybr pewter. Anyways its gonna be a full sized hammer. 20-22inches long, head length of roughly 9inches, and roughly 5inches wide... half will be aluminum welded into a hole cut into the tin. Wrapped in leather.
Im excited it will be my first casting project. After several tries i might move up to a chromoly hammer... a good 150lbs hammer that only few can wield. Lol.
Anyways message me any pointers or advice... i know thid is a veryyyy old post. But oh well.

merrypranxter (author)2014-11-08

I've been itching to cast my own jewelry. I am sooo glad i found this before my dumb impulsive ass got my hands on anything else I needed to do it. When i get excited about something I tend to get ahead of myself.... and none of the other tutorials i found put the danger quite so succinctly as you did. Of course i know that casting molten hot metals is dangerous.... but i really needed someone to spell out exactly how bad it could "f- you up". This instructable may have saved my life lol- or at least my face. I'm quite happy to continue wire-wrapping at this point. My boyfriend and i thank you for getting that silly idea out of my head.

it IS dangerous, but people have been doing it for thousands of years, with more primative tools, and metals that are a LOT hotter (like copper, or steel). So long as you're conscious of the risks and take steps to be safe, you should be fine. a few simple safety tips would start with:

wear cotton. or some other natural fiber. synthetics melt and cling to the skin, almost as bad as the metal itself

cast over dry sand. if you spill the sand will absorb the spills and largely negate the risks of molten metal splattering all over the place.

use long tongs of some kind, preferably those made for this sort of thing. this will keep your hands, and more importantly YOU away from the metal should things go south. and, you know, that cruicible is hot....

obviously face and eye protection are important.

above all, dont be in a rush. plan out everything you're going to do, and then make sure you know what to do in case things mess up. you'll be more prepared and less likely to panic. and should you mess up, dont try to stop it to save the metal. save your self. just like any other craft that's dangerous, trying to stop an accident that's already started is a recipe for disaster. even if it's gold your dumping on the ground, it's not worth the injury. just dont panic and you should be fine.

noahspurrier (author)2013-05-12

The density of tin is not similar to lead. It is much less dense than lead. Perhaps you were thinking of iron. The density of tin is close to iron.

ASTMB339 (author)2011-10-26

For what its worth -- I buy my tin from www.metalshipper.com. They're cheaper than roto metals and sell tin "shot" which is like little bb's that melt easily and make it easier to add the right amount tin you require.

ASTMB339 (author)2011-10-26

For what its worth, I bought my tin online from www.metalshipper.com. They seemed to be a little cheaper than Roto Metals and the quality of tin was good (came with a certificate of analysis). I also use a tin "shot" that makes it easier to melt and add to the pots then bars.

Father Christmas (author)2010-02-23

Ya know, I have never once had an issue with plaster molds. (other than the one time use problem) 

Well, I change that. I didn't completely melt the wax out of the mold and then kaboom-fizzle-burn  but that is about it. I still use plaster for casting tin.

atombomb1945 (author)2009-11-15

I am just going to borrow a quote here " With mine, it goes like this. pouring is easy, pouring is uneventful, hey, is it boiling a little in there... Holy splatter, batman!"

That boiling is the release of water that is still in the mold.  Fine if you are using time because of the low melting point.  If you were to have applied this to lead or a lead tin mixture, you would have had a small explosion and would have been nursing burns from 550 degree to 650 degree molten metal. 

I would highly recommend either the use of pre-formed molds from a hobby shop or the use of casting sands for custom molds.  If one were to use plaster for a casting job, it would be a good idea to fire it in a small kiln rather than an oven.  Better yet, get a DIY Silicon mold kit that can take the high temps and be used repeatedly.

Good points on the safety equipment.  Would recommend adding an exhaust fan or opening the garage door for the fumes. 

HarveyH44 (author)2009-11-14

I use to cast pewter (lead/tin mostly), and this is scary.  Concrete and Plaster of Paris retain moisture, which is released violently when you pour hot metal into it.  Tin by itself is kind of brittle.  I started with a cast iron pot on the kitchen stove, but eventually bought a melting pot.  Not sure how well stainless steel holds up over time, usually kind of thin.

seraphus (author)HarveyH442009-11-14

 Thanks for your input. Really. 

For my molds, I heated the plaster for 3 hours at 400 degrees to reduce the odds of it cracking and spewing everywhere. Dangerous, I know, but I was using what I had. I've edited the mold section to reflect the danger of plaster molds.

 I'm going to change some wording about my pot. Could you look through and see if anything in particular needs changing? If it is horribly wrong all over, just tell me, and I'll take it down, under the condition that you do an instructable over casting. 

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