Need a cheap way to make a mold of a fairly large object

I've never made a mold of anything before, but I have a statue that I would like to make a replica of. The statue is about 18 inches tall, 5 to 6 inches wide at its widest and 6 inches deep at its deepest. It also sits on a 2 inch high 10x12 base, but I don't really need to cast the base, I could fabricate a new one very easily. I read the featured instructable for making silicon molds and it was very useful, but I think silicon would be very expensive for this big an object. At least 3 gallons, I'm thinking. That would run at least 300-500 dollars, and I'm looking to spend more like 50-75. Is there another technique, or another material I could use? My sculpture I think is cast from resin, and I'm fairly sure it's at least partially hollow. It's not intricately detailed, but it's hand painted, so I don't want to use anything that will damage it. Could plaster work? Rubber? Cheaper kinds of silicon? What sort of material would be best to cast the replica out of once the mold is done? I'm open to any kind of material, in fact I'll probably try a few different ones. Plaster, resin, maybe plastic or even rubber if that won't harm the mold.

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lemonie8 years ago
You could loosely wrap it in plastic to ~0.5" thickness, then coat with a crude layer of paper and glue. Pull it out or split and re-seal, then use this crude paper-shell to make the silicone mould. You should be able to get away with 1L. L
UselessTrivia (author)  lemonie8 years ago
I think I see what you're getting at. I wrap it in plastic and then mould the plastic into something cheap, like maybe plaster or something? Would that be strong enough? Then I remove the plastic and fill the gap between the statue and the cheap mold with higher quality silicon. It's like the surface molding instructable only instead of making my part out of 2 different materials, I'm making my mold that way. I think that could work, I just need to devise a way to suspend my statue over the larger mold without it touching anywhere. I think there's enough attachment points on the back that I should be able to rig something where I can suspend it. Any suggestions on material to make my filler mold out of? Plaster would be cheapest, but I'm worried about it breaking as I'm pulling the mold off after casting.
I'm thinking of a cheap, rough papier-mache case (sealed tight up against the base, but nowhere else). You cut the top off above the head (assuming the statue has a head) and pour silicone in the top. It's positioned correctly by the attachment to the base. I say 1L, but I think that's an upper-limit.
Silicone is flexible, you wouldn't get plaster off in one piece.

L
UselessTrivia (author)  lemonie8 years ago
Is this kind of what we're talking about? Only instead of applying the rubber silicone with a brush, we're making that rough outer cashing from Part 2 first, and then pouring into the rest. I wonder if that stuff they brush on to make the outher shell would work for this.
A thin coating would work if it had adequate support (now you're giving me ideas). You're main point was that you didn't want to / couldn't spend the cash on a lot of silicone. If you surface coated this with something flexible, which would give you high definition, you could firm it up with something cheap (like newspaper) and save on bulk materials. Make an Instructable out of it if you do. L
UselessTrivia (author)  lemonie8 years ago
I'm torn. I have two ideas now that I think could work. one sounds a lot easier for a first-time mold-maker: Use a brush-on silicone to make a shell about 3/8ths to a half-inch thick. Then make a hard shell around the outside of that to keep it sturdy while casting. I think this mold will work fine, but I'm worried it won't hold up that well to repeated castings. The other idea is to do what you said: Cover the thing in plastic about a half inch thick, then make a mold of that plastic. Remove the plastic from the master and cast a thin layer of silicone between the first mold and the raw surface of the master. This would make a more traditional two-piece mold, whereas the brush coating would be sort of sleeve with a slit in it. I guess it just comes down to which will be cheapest to try. The reason I'm being so cheap is because this all for a prank. This statue has circulated around the family for a while and everyone thinks it's ugly as sin. I ended up with it last, so now I'm going to give one to everybody, but I don't really want to spend 500 bucks making a mold for a two hundred dollar sculpture and then 30 or 40 bucks on each casting.
There's also latex, but I don't know much about using it.
http://www.paperpeople.co.uk/mouldingcasting.html

L
you should change a mold,the company chilorson mold maker will help you.

http://www.cheapmolddie.com/
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peterpi7 years ago
This is easy to solve,contact nice mold, Email is nicemoldsz@hotmail.com,they are quite a big mold factory in china,but charge like small mold factory,trust me,you will save a lot for same product
UselessTrivia (author) 7 years ago
 Just to let everyone know what I ended up doing: 

I used a brush-on silicone rubber from Smooth-On to make an inner mold and then cast around the outside of that with plaster gauze wrap to make a hard shell.

The mold worked great, except for the fact that it was too complex of a shape to do with a brush-on material I think.

It is a statue with two legs and it has pointy ears such that you need to cut away each leg and each ear separately which leaves too many seams to cover up.

I'm going to be remaking the mold, this time as a two-piece block mold.  I'm still looking for cheap solutions because a model this size is going to take a good couple gallons of silicone rubber to make a 100% silicone mold.

My plan at present is this:  Take the original sculpture, wrap it very thickly in plastic wrap.  Then I'll make a  loose block mold out of something.  I was thinking plaster, but I want something that's going to be semi-solid to begin with and dries very hard.  Plaster is probably too liquid at first and too crumbly when dry.  Maybe I'll just use plaster with shredded paper in it to give it consisency and brush it with urethane or something when I'm done to give it a hard outer layer.

After I have a two-piece mothermold of this completed I'm going to peel off the plastic wrap from the original and give it maybe one or two quick coats on each half with a brush, then I'll lower it into the block mold and pour silicone rubber into the gap. 


What I'll have in the end will be a hard block hold that outlines the rough shape of the sculpture, and inside of that will be a 3/8th's or so thick layer of silicone rubber  that captures all the detail and releases easily.

If I'm lucky I can do this with about 50 dollars worth of silicone and 10-30 bucks worth of plaster or clay (I might even consider sculpy if anyone sells it in bulk for cheap, I've never seen a package bigger than a few ounces at the craft store.)
You could use Parafin Wax. Just coat the figure with alot of vasaline, cooking spray, or some other mold release. Lay it on it's side and build a frame around it sealing the bottom of the frame. Pour wax in up to the halway point. Let the wax harden and put wax paper covered in release agent on the hardened wax around the statue. Pour in wax to cover the rest of the statue. Once everything cools and is hardened, remove the frame and gently separate the two halves of wax, then remove the statue. Put the two halves back together and secure with rubber bands or straps. Drill a pour hole in one of the ends. Reopen and remove excess wax. then cast as normal.
Try plaster, just cover the statue with some thin wax paper or painters tape. possibly you can even use jello, or this