Making of a (plastic) goatThursday, July 17th, 2008
The project: to make multiple copies of the goat to attach to keychains. The question is, how does one do this? After inquiring around the UK about producing them from a 3-d model, smaller companies said they couldn’t do it. The other option was to get it produced in China. Minimum runs are at least 1000, and I wasn’t sure if I *REALLY* wanted 1000 plastic goats (now I think I do, but when I started all this, I was nervous about the number). So I started looking into making my own silicon mold, filled with poly-eurathane (plastic).
This post will go through my entire process of making a two sided mould, and detail all the stuff I learned, and show you my (limited) successes!
Step 1: Getting the materials
I found a place called TOMPS that sells mould making materials of all sorts. Their website isn’t exactly beautiful, but it has a good check-out system. I couldn’t figure out exactly what I wanted from their directions, so I called up the guy, and he was EXTREMELY helpful, and told me what to order. I ordered:
- 1 x Polyurethane Fast Cast Resin Option: This is to pour the goats once the mould is complete
- 1 x Alginate 500g*Alginate Setting Speed : Fast – 4 to 5 min set: This is to fill in half the mould while I’m making the other half (you’ll see!)
- 1 x RTV Silicone Rubber 1kg *RTV Hardness : Medium *Catalyst Speed : Slow – Potlife 40 mins: This is to make the actual silicon mould
There’s a few other things you’ll need:
- Rubber gloves
- Measuring cups (get new ones from the pound store)
- Some sort of container to make your mould in(I used a lid from a spray can, but I suggest you make something square)
- Area you can leave your mould to cure (well ventilated is better)
Step 2: Making the original
I wanted to make a really tiny goat, but my skills at sculpting resemble something closer to a deranged 4-year old than an artist, so I made my little guy a bit bigger. I used femo (which you can buy from any craft or art store) and then baked it in the oven. Make sure your hands are very clean, and make sure that everything is well stuck together. The tail of safetygoat didn’t come off when I originally baked him, but it seemed to have fallen off at some point! Be careful of baking as well. My details on the ears folded a little, and my first two goats I over-baked and they shrunk down. You really only need to put it in on low heat for 20 minutes or so to get it hard.
Step 3: Making the mould-filling container
I found this video from tap plastics on Youtube on how to make a mould box (and they have a hilarious jingle… tap! tap plastics!) but since none of my local shops carried the acrylic they suggested, I decided to use a cap from a spraypainting can. This is not ideal, for a few reasons: 1. This shape is round, so you have to do a bit more forward thinking in where the top of the mould is going to be 2. I had to cut out the bottom of one lid and then hot glue another one to the base. Like I said, not ideal, but it worked, so I say, be creative!
Step 4: A two sided mould requires some sort of fake filling
First thing you have to consider is how you’re going to fill the mould, and where the cut line will be for the two halves. I decided to fill up the goat from his four feet, so he was upside-down with his little hooves in the air.
The guy from TOMPS suggested I use Alginate to fill up half my mould first, stick some marbles in it, and then pour the silicon overtop. This sounded weird to me at first, but I guess the reason why you do it is so you have some sort of ‘clasp’ to attach your two mould halves together in the end.
First you mix up the alginate as described on the pack. It’s the coolest stuff, and hardens in 5 minutes (apparently, it’s also great for making moulds of things like kids’ hands because it’s made from seaweed, and completely non-toxic). I was a bit of an idiot and didn’t have any marbles, so I used coins, but they are much too thin and didn’t make a good clasp. Even a rock would have worked better for this. What you do, is, as the alginate is hardening, stick your marbles half-way in, so that half of them are protruding out. Make sure this is completely dry.
Step 4: Pouring silicon
How much do you use? Â What colour should it be? Â I made a lot of mistakes as I didn’t have a scale… but it is very important to get the proportions right. Â If you don’t, you could, like me, have a mold that doesn’t set after 24 hours (this happened on the first half). Â
When I poured my first half, I didn’t add much of the blue stuff as it said 9:1. Â Look how light the top bit was. Â It is way WAY too light. Â It actually took more than 72 hours to set, and that’s after I put it on the heater. Â (The guy suggested I put it in an oven, but ONLY if it was not an oven for cooking…he obviously thought I was in some sort of *proper* workshop and not my living room with my roommates complaining about the fumes!)
Step 5: First half complete… now for the second!
I had to flip the guy over, and take out the alginate so that I could pour the second half. Â The alginate was fun, but a little bit wet at the bottom where the water had pooled when I poured it. Â In hindsight, I should have took the bottom off and let the alginate set a bit more. Â I dug it out with a knife, and cleaned off the mold as best as possible. Â The set portion of the silicon was very rubbery (due to my mistakes withÂ quantities)Â but it held firm. Â I also removed the pennies, so the second half would fill in the bits.
Step 6: Pouring the second half
Now this is the second side. Â Do you see the difference between the shade of blue from the other half? Â This side set easily in 24 hours. Â Notice also that his little hoof is sticking out a bit. Â The other hoofs were barely below the surface (I actually meant for there to be two hoofs showing, but it wasn’t a good surface I was working on…. I ended up puncturing the left front hoof when it was set so that the air could escape). Â This hole is where I planned on pouring in myÂ urethane.
Another thing: Â Don’t try and clean up the silicon or the urethane yourself. Â The guy told me to wait for it to set. Â It is probably the most gruesome cleaning thing I have ever tried to do… but once it’s set, it peels right off!
Step 7: Removing the model from the mould and…. casting time…!
It worked! Â I cut the mold out of the plastic container and got busy making the cast. Â I made WAYY too much mixture the first time (Part A and Part B, as pictured, are poured in equal measure), but got the hang of it for the second. Â Again, make sure you mix things properly! Â Cleaning half mixedÂ polyurethaneÂ from a mold is IMPOSSIBLE! Â Look what happens if you don’t get the proportions right:
He is sticky and gross! Â He never stopped being that way!
As you can see from my photo, I used elastic bands to hold my mold together while casting. Â Each cast takes about 30 minutes to set, so it’s a great activity to do while watching tv. Â MAKE SURE YOU WEAR GLOVES!!! Â My hands were KILLING me after. Â And make sure you’re in an area that you don’t mind being dirty forever…my poor roommates!
Step 7: A decent copy….Maybe I should paint him?
Here you can see the two sides of the mold below and my final goat! Â His tail may have fallen off and there may have been an air pocket in his nose, but for a first go at this, I’m pretty chuffed. Â I think he’s adorable! Â I am now going to make a new mold, after learning these lessons…
- Make sure all bits of the original are secure!
- Plan the seam of the two sides carefully so that you don’t get air pockets, and it’s easy to pour
- use a square container
- Measure proportions CAREFULLY!
- Wear gloves when dealing with these toxic materials… they don’t come off easily and sting the hands
Maybe I will get some done professionally from a 3-d model I’m making…. but I thoroughly enjoyed this new medium, and it’s no where near as hard as I expected! Â I get the feeling the next one will be 100 times better. Â Until then, you’ll have to wait for your plastic goat
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