I bought a cobblestone street section for my diorama and I was wondering if the any of you has done cast molding.
I want to make a cast molding from that cobblestone street.
I'm open for suggestions?

Hi,

it is quite easy.
you will need the following:
- laminated wood
- bracket
- nails
- rubber in the silicone (handling and hobbies shop)

Take the mesurement of the part you want to copy.
Add 1/2 inch on each size(1/2 + size + 1/2)
Add 1/2 inch to the thikness of your part.

Draw on the laminated wood the part to be copied.
A rectangle to which you add the 1/2 inch.
You now have a bigger rectangle.
Nail the bracket to do rectagular mould.

Lock the part to copy in the bottom of the mould with clay (for exemple) in the center = small rectangle draw.
Do the volume to be put in the mould.
Melt the hardener to the silicon rubber (follow the manufacturer instructions)
Use an old brush to put small quantity of silicon on the details part.
You will avoid bubbles and get a clearer mould.
Once all the surface of the part is rubber covered, put the remaining
silicon in the mould from a corner(do not move)

Once you have put the silicon in the mould; shocked slowly.
You will help the bubbles to go up.
Less bubbles in the mould , stronger it will be.
Let about 24H, until the silicon has hardened.
Remove the bracket.
You now are able to see your new mould.

unmould gently the original part.
You are now able to mould new parts, plaster resin.


Hope that you will understood my talk beacause it would have be easier in french, for me at least

Thanks got it

I just want to add that you should calculate the real need of investing for the "not so cheap " silicon instead of buying one more copy of the original piece.
You may eventually never need more exact copies for other projects.

I scratched already 2,5 meters of cobble street for my dio and did no copy of parts of it because there are no two exact segments anywhere.

Jut for thoughts

Claude

Thanks you are right

David,

You might also consider a latex rock mold making material like what is used by model rail roaders on their layouts:

http://www.walthers.com/exec/search?quick=mold%20making&start=0

It's a lot cheaper than going the RTV route, and it also might be easier to source locally. You can find this stuff at model railroad hobby shops or one of the big box crafts stores like Michael's or Hobby Lobby.

Not what you'd want to use to replicate model detail parts but perfectly good for plaster scenery stuff like your cobble stone roadway.

HTH,