With my last semester for my Bachelor's underway, my wife and I were busy on the side creating steampunk Bonnie and Clyde costumes for the upcoming Salt Lake Comic Con. I had chosen to simply modify a couple of Nerf guns, considering I was trying to finalize the thesis for my degree. One night at work, I get a text from her saying, "We're putting a rush on Bonnie and Clyde. The Old Man's going to be at con! We're doing BSG uniforms and we need guns." Job, Internship, Senior Thesis, Family. Less than a month before con. Do I have time for scratch build six replica guns? Pssh, I'm game!
When it comes to cosplay, the question is never "Why?" or "How?" but "Why the hell not?"
This Instructable will teach you how to use a layering technique with foam pvc or a similar material (mdf is a great alternative) to create guns or other intricate props. It will also introduce some of the basics of silicone mold making and resin casting.
Step 1: References
As always, begin by collecting reference photos! I can never overestimate this step of the prop building process. With this project I literally had less than a month to go when it was dropped in my lap. This is a short period of time for me and sadly my rushed efforts caused me to miss out on some really great references. C'est la vie.
Here's the main reference that I worked from. As you can see, there are a lot of recesses and details with this sucker. I've never been terribly interested in re-creating guns, but they are intricate and I do like a challenge!
In addition, six of us were dressing up in these uniforms. With the time frame, and the fact that six of the exact same piece were needed, it was the perfect opportunity to try my hand with a two-piece silicone mold and large scale resin casting. I brought this fact up with my wife and she reasonably (considering she demanded them) allowed me to order the supplies. Score!
Step 2: Patterns
Normally I prefer to create my own patterns but again... time. So I hopped on over to the prop shop of Bill Doran, Punished Props, and purchased his blueprint. This probably saved me two hours. Not a ton, but every little bit.
To start, I printed out ten copies of the blueprint. Then I reflected it and printed out 10 more for the opposite side of the gun. As was mentioned, there's a lot of detail to a carefully machined piece like this. That means that layering, as is often the case, was the perfect method of construction. I began planning out how I would slice the gun up into parts and then starting slicing out sections with my x-acto knife. Initially there were more than 30 pieces, and I added a few later on in the build. Woo!
Make sure you label everything. Left, Right. Trigger. Safety switch. Whatever makes sense to you. When you have this many slices, you're bound to forget what you're looking at from time to time.
Step 3: Props Are Like Ogres... Uh, Onions. They Have Layers!
My M.O. in the past has been to print my patterns out on card stock to make it easier to trace onto my material. Normally I stick to MDF because it's cheap and works great. For this project, though, I chose PVC Foam (a common brand is "Sintra"), a lightweight, easy to shape plastic that comes in a variety of thicknesses. Most desirably in this situation, however, was that pvc foam works perfectly with super glue, meaning minimal down time waiting for things to cure.
The fact that it was plastic freed me up in another way. Instead of tracing my patterns, I sprayed them with 3M General Purpose spray adhesive and stuck them directly to the plastic. Then I cut out each section on my scroll saw and later peeled off the patterns. You'll use more paper this way, but you'll save time in skipping the tracing.
Tip: If you have difficulties peeling off the patterns, dab the pattern in some mineral spirits and wait a minute for it to soak through. It'll peel right off and if you're using plastic there's no concern of staining your material!
The first two photos here are from a different project, but it will demonstrates the point.
After you get all your pieces cut out, stack them up to make sure you've got good fits. Check and double check everything at each stage of your project. This will save you headaches down the line.
Step 4: Shaping
I wish I had more photos (or better, a video) to guide you in this process but the fact is that I get so focused I often forget to document during this period. I use a Dremel with a sanding bit for 80% of the work. The remaining 20% is a variety of needle files, various grits of sandpaper, or the occasional grinding and engraving bit. I started by shaping and gluing the main frame of the gun. Once everything was how it needed to be, other pieces were added: grips, various rails along the side of the barrel. The two halves of the slide action were each crafted separately. So was the grenade launcher attachment.
Once everything's shaped, break out your Bondo. Bondo is an automotive filler typically used to fill in car dents and dings but as you'll find, it's widely used in propmaking. Anywhere you see unsightly seems or low areas, mix up some Bondo. Wait about 20 mins for it to cure when it becomes unworkable. Then sand the areas smooth. Anywhere in the photo you see pink stuff, you're looking at Bondo. You may need to do this several times to make a nice clean looking piece.
In the last photo you can see a gray material at the front of the slides. If you look at the reference, there appears to be some holes at the front of the slide. Vents or something. I don't know. For whatever reason I drilled these in from the 'top' of the slide originally, instead of the front. It looked beyond wrong, so I filled the area with Apoxie Sculpt. This is a two part epoxy that is sculptable like polymer clay for two hours. After 24 hours it cures rock hard and becomes sandable and machinable. I re-drilled from the front ends of the slides and the results were much better.
Mistakes are a part of prop building. Don't get discouraged (for long). Keep pressing on and eventually you'll get what you're looking for!
Step 5: Primer and Wet Sanding
Once everything's glue together, seams filled, and your piece looks like an actual, 3D object, you can start thinking about the molding process.
You want your piece to be smooth and shiny. Silicone picks up every. little. detail. With this in mind, give your entire piece another pass over with a higher grit sandpaper. Preferably something over 2-300. After that, I use automotive filler primer and paint the whole piece. When that's dried, begin wet sanding. By this point you're sick of sanding, I promise, but getting up into the 1000s will make your prop so smooth you will not regret it. In fact, you'll spend at least an hour after your done petting your project like you're Gollum with the One Ring.
"Sooo smooth, Precious..."
It's okay, you deserve it. Any longer than an hour though, and your family will be dialing up those men in white jackets.
Besides, you've got silicone waiting!
Step 6: Mold Box and Clay
Now that you've moved past the marvel of your smooth prop (at least that's what those fools think >.>) you'll want to make the first half of your mold. The first think that needs to happen is to submerge half your master sculpt in clay. It is important to note that your clay must be SULFUR FREE, otherwise it can/will inhibit the silicone from curing. Clay up your master sculpt before you construct your mold box. Believe me, it's a pain trying to get that stuff into every nook and cranny with the walls of your box in the way. Also, coat the back end of your master sculpt with mold release before applying clay so that the clay's easier to clean off afterwards.
Leave yourself about an inch all around your piece. Then, using some kind of tool (I used the top of a nail polish brush :D) make indentations in the clay all around your model. These will create bumps in the first half of your mold known as registration keys. These help your mold to line up properly during the casting process.
(Side note: I actually broke off the trigger during the claying phase. I spent about 10 mins frustrated and pissed. Then I realized that there was no way to keep it from trapping air when casting, and that it was best off creating a one piece pour mold of it separately anyhow. Sometimes mistakes turn out for the better)
Finally, construct your box. I used MDF. The edges were sealed with hot glue. The box must be made of a material which does not absorb the silicone. MDF worked fine here, but probably was not the best choice. For the trigger's mold box, I used pieces of a Raisin Bran box with the outer surface facing inwards with no problems.
For one piece block molds, simply construct a box. Attach your piece to the bottom of the box in some fashion. I prefer using double sided tape for small items such as this. Hit it with mold release and then cover it in silicone.
Step 7: The Waiting Game
Once your piece is snuggled in its clay and mold box, give the whole thing a hit of mold release (I use Mann Ease Release 200 with Mold Max products). This is an agent the prevents the silicone from adhering to your piece or to the walls of your box and simply makes it easier to remove. The silicone I used for this project was Smooth-On's Mold Max 40. It should be a mint green color when it cures.
When you're pouring your silicone, go slow. This stuff has a cure time of 24 hours, so there's no rush (beyond your own impatience!). Mix thoroughly and pour from high up. This will stretch out the stream of silicone as it falls and hopefully cause some air bubbles to pop. Start in the lowest area of your mold and let the silicone flow naturally up and over the high points until the whole thing is submerged.
Mold Max 40 is optimal at a temperature of 73 degrees (many, most, silicones are). For safety's sake I poured it outside. It was still a bit too cold though, so once I was certain there were no leaks in the box, I brought it inside my home to cure. Our cat, Yuffie, is quality control and inspects everything we do. After a cursory inspection the mold was approved.
24 hours later, remove your walls and the clay. DO NOT remove your master sculpt from the silicone. I learned this one the hard way. If you remove the master sculpt from the silicone, you run the risk of the second pour sneaking into areas the first half had covered, requiring clean up, or just plain ruining your hard work. Be careful to clean off every little bit of the clay from the back side of your master sculpt or the tiny bits will leave minute impressions in your mold that will show up in your castings.
Step 8: Surgery With Silicone... Pour Spouts and Air Channels
Re-construct the walls of your mold box around your master sculpt, which should still be snuggly seated in the first silicone half. Blast the whole thing with mold release. Silicone will adhere to silicone without this and you'll end up with a big block of rubber stubbornly hoarding the hard work of your gun!
Mix and pour your silicone using the same techniques as before. Then wait another day. Afterwards, retrieve your brand new mold. Remove your master sculpt and determine where in your mold your pour spout will be. The best spot is usually a broad, flat area on the model which can be sanded easily. Once you've decided, cut out a channel from the silicone using an x-acto knife.
When you know where your pour spout is, you will also know which side of your mold will be facing up. Use this to determine high points in the mold that pose the risk of trapping air bubbles. Here the bumps in the grip, the forward arch of the trigger guard, and the front ridges of the 'rails' on the barrel all warranted vents.
Again using your knife, cut narrow channels from these areas to the top of the mold. This will allow air to escape and prevent creating air bubbles in your castings. A major nuisance!
Step 9: I Can Make Nearly Perfect, Nigh Unending Copies of My Work? ... Cooool
Casting is simple in comparison to everything leading up to it.
First you need to properly treat the inside of your mold.
Spray both halves with mold release. Hit it from a couple different angles just to be sure. The resin I use typically is Smooth Cast 320. Plastic cures with a super shiny surface. While pretty, and almost as Gollum worthy as your completed master sculpt, this is terrible for holding paint. So after you treat the inside of your mold with release, get yourself from talcum powder and a kabuki makeup brush, and dust the inside of your mold. This will make it easier to remove, but also cause your casting to come out with a paint ready, matte finish.
Once it's prepped, place the two halves of your mold together, making sure to press your registration keys into their recesses. I cut sheets of MDF to roughly the sides of the mold. Place one on either side and then clamp them. You want it snug, but not too tight or it might cause warping to your mold. The MDF boards wil help to evenly distribute pressure.
Mix up your resin. I added black resin dye so that con damage to my paint jobs wouldn't show as badly. Unfortunately, because I was worried about cure inhibition, they only turned out gray. Live and learn.
This particular type has a pot life of three minutes, which means you have approximately that amount of time from mixing to get the resin in your molds. Pour it in, and once your done, tilt your mold from one side to the other giving it a few bonks to knock loose any trapped air. Let sit. Cure time for Smooth Cast 320 is 10 mins. I usually give it 20-30 just to be safe.
Step 10: An Unending Arsenal!
You can tell I never did find the correct ratio of dye to resin with the first batch. Nevertheless, it was incredibly exciting when I laid out all six guns after casting. There were some pinholes to fill, flash to sand smooth, and minor other imperfections to fix, but they looked great. Another full day of painting and I had the entire set ready to go for our Photo Op at the con with Edward James Olmos. Both he and Chief complemented me on my work, which was amazingly gratifying.
I hope this was of help to you. If you have any questions, feel free to leave them in the comments and please like us on Facebook. It's easier to get a hold of me there and I post photos and updates on current projects as often as possible! I also do commission work.
Unpainted resin casting of this gun are available for purchase here.
Thanks for reading!
SO SAY WE ALL!