Trying out pewtercasting

[mlkr]

Being the kind of person who always wants to learn more and do new stuff I decided to try out some pewtercasting.
Went and bought me some heat resistant RTV-Silicone and did a mold for storing pewter. I used a bar of chocolate as my original and created a mold wich will let me break of suitably sized bits of pewter.

Mold was done yesterday and today I melted some pewter and did a cast. End result is a bit strange though. The pewter is full of bubbles. There is to much of it to be air and as I did a slow and steady pour from a corner the result must be because of something else. My guess is the so called heat resistan silicone isnt really that good. It was a bit singed and smoking when I took out the casted pewter...

Mold was preheated and pewter was clean so I really dont know what it could be. Any thoughts? Anyone with experience who can tell me what went wrong? thanks ^_^

[marell le fou]

Good try.

How long does the melted metal makes to solidify after you put it in the mold ?

[mlkr]

Thanks ^^ Will see what can be done about the sketchy results...

It's pretty  much solid within a minutes time, but still very hot to the touch!
I guess cooldown-time is dependent on the amount of pewter in the mold. This 500 grams bar took quite a while to cool down when in room temperature. Placing it outside did short work of the heat though ^_^

[jchaos79]

Never cast before, but I wonder if the bubbles could have to do with deficient preheat?

[andydorman]

 Haven't tried casting yet either but apparently it's ready when you can dip a matchstick and it smokes - not sure if that's helpful or not?!

[Aldhick]

You already got the answer on FB... I don't know the precise term in English - in our language it's callet the "surface tension". To eliminate it you need to powder the surface of the mould with graphite or french chalk.

[andydorman]

Ah yes of course! Powder is also vital - and Aldhick knows his stuff!!

[mlkr]

Will look into this and order some tonight
Have to work like crazy coming days anyways so wont have that much time to try anything for a while ^^
Thanks for the tip here too

[mlkr]

Just a quick update - The chalk really helped and I was able to get very nice casts with it. The mould would go very hot after a few rounds though and would then produce slightly worse results.

Anyways - All I ahve done is melt down some old pewterobjects into smaller bits for later usage. I dont have anything sculpted to cast anyways so this learning project will be slow going.

[forbes]

I don't know anything much about casting - but can see that you are using a huge amount of metal in proportion to the mould.

If you were casting figures you would have far less metal and far more mould - which should help with cool down time.

[mlkr]

Yeah - I stopped filling up the mold like this at second try. Only poured the individual pieces instead but it is still a lot of heat generated so the mold probably runs too hot.

Still nothing new to report though :/

[mlkr]

Wanting to try out how good details I could get from future sculpts I picked a small 6mm figure from an existing line that I have lots of and did a mold and cast. Details are good but not supersharp. Still pretty impressive.

Timeconsuming and expensive materials though so it will be slow going to experiment further.

Yes this is technically a recast - used to test and learn for future castings of original sculpts - bought or created by myself.

[Geep]

That looks very good to me. How did you make the cast? Any fancy techniques?

[mlkr]

The small stuff like above looks better than a few 28mm i tried. Sharp details got "rounded off" more noticably. No fancy tech used 2part mold in heatres-silicone with pour- & ventilation-channels cut to allow good flow of pewter. Heated it on my stove so no idea about temperatures. Some talqum and thats that.

Moldslippage and loss of details occured so I will have to work on this a bit more before I can say it's viable for anything but for fun

[calmacil]

Mould slipping can be an issue. Our company uses silicone from coker, but we've recently changed suppliers and it's got rid of the issue.

A possible cause of slips lines is when one half of the mould is hotter than the other side. This is usually the top half (side with the hole in it) because your top plate overheats. One solution is put your moulds on the floor to cool them both down