First casts

**turnerted** · 14th May 2014, 12:34 PM

G'day.I've decided to dabble in the black art of casting.I have never done any casting but have had quite a bit of experience working with fibre glass.
Rather than cast pen blanks I wanted to do something different.As I make lots of bangles I decided to try casting some with inclusions.The pictures show my first two attempts.One with gumnuts and one with sheoke cones.The third picture is of the plug used in making the silicone mould.They are not perfect but encouraging. These were sanded to 400 then Scothbrite fine, then ultra fine then finished with EEE.
I have some questions.I found sanding polyester a pain with the way it clogs the sand paper and was tempted to use wet and dry but was concerned I might get moisture in where the inclusions come to the surface.
I have just taken my third casting out of the mould and I have noticed that I can see evidence of the two previous castings on the surface ie there are slightly patterns of gumnuts and sheoke cones evident.It seems there is a memory effect in the mould. My first use of the mould was probably the day after I made it and the second probably two days latter.The mould was probably a week old when I made my latest cast.Do moulds take a while to cure?
I am greatfull to dai sensai and Brendan Stemp for their videos.

**Dorno** · 14th May 2014, 08:15 PM

Do the CA process that we use on timber pens after you have sanded the bangle up just put a couple of coats of CA on it then use some micro mesh to finish it off the polish it and thats should solve any problems ?

Cheers Ian

**gawdelpus** · 15th May 2014, 08:11 PM

The molds should be ok ,but the PR can shrink slightly ,maybe leaving the harder inclusions to impact on the mold slightly ,and as dorno says ,you may need to use CA as a finish to properly seal the included bits ,another "dARK ART" at least you can then use wet and dry, or preferably micro mesh to get a mirror shine on you castings ,also you can use "0000" steel wool to remove minor sanding scratches ,before other finishing processes . Cheers ~ John

**dai sensei** · 15th May 2014, 08:26 PM

Not sure why your silicon mold didn't set properly, the only reason that happens usually, is that the catalyst/fixer component was not mixed in properly. Silicon instructions normally talks about double mixing, ie mix in one container, then transfer mix to another container and mix again. I use a coloured pigment additive so I can see it has been mixed properly.

As for finishing, the surface will definitely need sealing with CA or lacquer etc, to seal the timber bits exposed.

**turnerted** · 16th May 2014, 04:56 PM

Thanks for the suggestions.Looks like I'd better finish with CA.
Neil My next silicone on order should be coming with coloured catylist,
Ted

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