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Resin Casting Question

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1st post on the forum (great forum BTW)...

I've done some casting previously, but not an expert by any means...simple 1 part molds to duplicate small 2 dimensional parts. I'm aware of some techniques for 2 part molds, and was wondering- I've purchased a vintage kit (for far too much $$) of the first car subject I built (in '75) and wanted to make copies of the wheels, exhaust and blower scoop to complete a re-issue that was recently released, with vintage box art but minus those original parts shown inside. My plan was to use the putty on the back side of the original pieces, pour the RTV over putty/master in the mold box, then eventually do the back side of the mold over the cured RTV and master, with a suitable mold release in between. Some of these parts are chromed, and I was wondering if the mold making process is likely to damage the plating on the originals, or whether the plating is likely to survive contact with RTV, putty and mold release.

Is it worth chancing without having to send vintage parts out for re-plating afterwards? Any brands of RTV (or other suitable mold making supplies) kinder to masters with delicate finishes?

I'm part-way into building the re-issued kit, and was really disappointed to find it was missing the period pieces shown on the box art- the way I built the kit the first time. I've raided some other re-issues for the required front and rear tires, so they're not a problem. My hope was to cast some copies of the missing parts, chrome them with Alclad II, then keep the molds and masters intact so I could either keep or build the original kit at a later time without doing any damage to it. I wouldn't need to make a whole lot of re-pops, but wouldn't mind a few spares should I get the urge to build another one of the re-issues as well (loved that original kit).

Any tips or suggestions would be appreciated.

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FYI - If you do use clay to assist with your mold-making, ensure you are using a sulphur free clay (check the lable). Suphur in the clay will prevent the RTV from properly curing. I think Micro-Mark sells such clay, but I was able to find some at my local Micheal's.

I'm certainly no expert caster, but I think I would also strip the chrome off the original parts to be molded just to be safe. It might also be a good opportunity to clean up any casting lines on the original parts too, before you mold them.

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