Pewter casting experts... please chime in...

[JOATRASH FX]

Hey all,

I've been trying to do some pewter casting in RTV molds for my Jubal Early pistol but I'm getting the "usual" rough/pitted/bubbly surface on my castings. I've scoured the net already but there doesn't seem to be a lot out there besides trying varying temps and making sure you've got a good release agent.

Some facts:

- Not 100% sure, but I think the metal I am using is a pewter/lead/some other metal mixture

- I am using graphite powder as a release agent 'cause I saw another prop maker using it when casting Imperial Officer disks.

- I am currently casting at about 250 degrees celcius... I doubt I can get it hotter. However, I might actually be going a bit too hot so I'm gonna try to cool it down some and see what happens.

- The thickness of the cast seems to play a big part. Thin areas look better, but real thick casts (like my pistol body, which is almost an inch thick) are affected most. It's almost as if the surface gets worse the longer it takes too cool.

- I've read than soldering paste is pretty good as a release agent (at least for thinner casts), so I'm going to try that as soon as I get my hands on some.

If anyone has any other tips, feel free to chime in.

 

[SaberFreak]

From what little experience I have about pewter casting during my time working for a pewter manufacturer, I believe casting temperature need to be 300 degrees celcius. The release agent I saw being used was sprayed on from an aerosol can. What's in the can, I don't know.

I also know that even for the pros, they need to play around with the temperature and cooling time for quite a bit EVERYTIME they cast a new item. Placement of the mold may also play a part as I've seen them lying the mold on different sides when they were experimenting.

The pewter mixture I'm familiar with is mainly tin (98% if memory serves), with a small proportion of copper and antimony to strengthen it. Lead is no longer used in modern pewter because its toxic.

Hope that helps.

 

[replicaprops]

The thicker the casting the less likely you will get good results with gravity casting. You will need to do spin casting.
If the casting is over .25" thick, even spin casting has its limitations, and must be heavily vented. For my Smallville keys there is close to 100 vents.

The main thing to do in gravity casting is warm the molds to prevent bubbling.

You can do this by pouring a casting, then dump it right after it is hard then pour again in the hot mold. You will need to powder the mold right away though to limit the mold from cooling down.

Lead pewter is horrible. You want the stuff that has 99%tin. About $12-$15 per pound.

You can also do lost wax casting or sand casting to get better results. www.backyardmetalcasting.com

In all home casting of metal is an art and nothing like resin or FG.

 

[JOATRASH FX]

Thanks for the tips guys. The last time I tried any metal casting was ten or so years ago and then it was only small stuff (25mm figs). Since I'm only looking to do maybe 5 pistols or so I won't be investing in any advanced rigs.

I'll be trying out some stuff tomorrow. For some reason, burying the mold in sand while casting seemed to help a little. I got castings that I might be able to salvage with a little buffing and sanding. I'm trying to find out for certain if there is any lead in the metal or not... it looks pretty bright and shiny (no dull lead surface) and it was pretty expensive, but there's probably an even chance either way. I'll give the molds a blast with my heat gun while the metal is melting.

The thicker the casting the less likely you will get good results with gravity casting. You will need to do spin casting.
If the casting is over .25" thick, even spin casting has its limitations, and must be heavily vented. For my Smallville keys there is close to 100 vents.

The main thing to do in gravity casting is warm the molds to prevent bubbling.

You can do this by pouring a casting, then dump it right after it is hard then pour again in the hot mold. You will need to powder the mold right away though to limit the mold from cooling down.

Lead pewter is horrible. You want the stuff that has 99%tin. About $12-$15 per pound.

You can also do lost wax casting or sand casting to get better results. www.backyardmetalcasting.com

In all home casting of metal is an art and nothing like resin or FG.

 

[JOATRASH FX]

Hey guys,


Just wanted to say that I did some casting yesterday. I went and exchanged the pewter I got for (more or less) pure tin. I noticed immediately that the melting point went up quite a bit. My portable hotplate is now taking a lot longer to melt it down. I had some pretty ok results, especially after getting the molds really hot after a few castings. Not perfect, but smooth enough to be buffed and sanded. Since each casting of the pistols main body takes so long to cool, I'm going to try baking the molds before pouring to get an even temperature in the right from the start.