Guitar Hero Hacks: Key Molding




About: I'm M@. If you know Prototype This, TechShop, The Best of Instructables, Show Me How, or AVPII: Requiem, you've seen some of my work and the cool stuff I've been involved in. I build and design and make and ...
I recently modded a Guitar Hero controller at the behest of fungus amungus. He's heading up the overview, and I'm going to show you how to create duplicates of your GH Controller keys in frosted clear plastic.

I'm going to review two types of molds using the same materials and principles. The first will be a simple block mold. The other will be the same block mold but it will include multiple castings. This is often called a gang mold.

You're going to need:
  • RTV silicone. I will be using Smooth-On OMOO two part silicone molding compound. This is fairly easy and inexpensive to pick up. You can order it online or at some craft and plastics stores. Any RTV (or Room Temperature Vulcanizing) silicone will do. For this process the Polyester casting resin I will be using has some cure inhibition (meaning that it will remain sticky) against tin cure silicone (your standard inexpensive RTV). This means that to get good parts out of the mold, you will have to coat the mold in sealant before casting your parts, bake the parts after they're cured, or apply a clear sealant to the parts after they are molded.
  • Latex Gloves
  • Foamcore
  • Stirring sticks
  • A digital scale or graduated measuring cups
  • Bondo car body filler. You can pick this up at most hardware stores and auto shops.
  • Clear Polyester resin. Find it at a plastics store, or order it online. Sometimes craft stores will sell this as a way to make cutesy paperweights with flowers trapped in them, etc.
  • MEKP catalyst. This will often come with your resin. You can also find it as fiberglass catalyst in most hardware stores.
  • Polyester resin dye
  • Respirator, ventilation system, or open well ventilated space to work in. Be mindful of your neighbors, as the polyester resin smells something awful, and will cause some people with sensitivities to feel ill.
  • Hot glue
  • A mold board. Any piece of smooth wood or plastic will do. Remember to seal the wood before casting on it, or else the mold will be difficult to remove.
  • Disposable paint brushes
  • Plenty of paper towels
  • The touch
  • The power

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Step 1: Dismantle Your Controller

It's time to suck it up and take the screwdriver to this fancy bit of extruded dinosaurs. You must remove the main body panel before the neck will unfasten. Once you've opened the neck, take a small electronics screwdriver and carefully take out the circuit board (you are saving all the parts, right?) Remove the keys, and take their rubber bumpers off. The rubber bumpers will fit perfectly into the new keys once everything is done.

Step 2: Single Key Mold

This is pretty simple and straightforward. You lay a single key down on your mold board. Then you cut the bottom off of a disposable cup, and hot glue the top portion to the mold board around the key. That's it. You're ready to mix up and pour.

Step 3: A High Pour

Check over your mold and part to make sure there aren't any dust, grit, or fingerprints that will screw up your casting. Remember that whatever you see here will show up in your final parts, and there's no way to correct a screwed up mold. A few extra seconds of inspection will save you the massive headache of recasting the whole part.

Mix your silicone according to the manufacturer's specifications. For the OMOO the instructions called for equal parts of compounds A and B. Stir your mixture for at least a minute, making sure to scrape down the sides and bottom. Try not to whip bubbles into the mix by moving the stick in and out of the mixture.

One of the crucial factors in making a successful mold is making sure there are no voids or bubbles in your casting. This means you pour your mixture from high above the mold in a very thin stream. This stream will pop the large bubbles that would have been included in the casting. Start in one corner of the mold, and let it fill evenly to the other side. When you've poured enough that you can only see the top of your key, go in with the paintbrush, and make sure there's silicone filling up the small divits where the rubber bumpers were. Now you can fill the mold until your silicone is about 1/4" above the level of your key.

Step 4: Gang Mold

This mold is simply a slightly more complex version of your block mold. Start with several rectangles of foamcore. Adhere them to the mold board, and then spray them with a sealant or shellac. Then glue down your parts with a daub of hot glue, this makes things a little simpler to arrange and cast. Fill this mold with silicone exactly as prescribed in the previous step.

Step 5: Casting the Plastic Keys

The Polyester resin I used was clear. For the translucent frosted look I was going for, it had to be modified a little before casting. For a frosted look, you can apply a crystal clear spray into the mold in a thick coat before molding. When the parts come out of the mold you can wipe the spray off of them with acetone. For a super smooth look, you can spray PVA mold sealant into the mold using a Preval Sprayer. It will form a super shiny water soluble layer in the mold. When your parts come out, rinse them in water to reveal a remarkable shine.

To begin, I measured about an ounce and a half of resin on a digital scale. I marked how much resin was in the cup with a marker and measured its height. Then I transcribed that line onto another cup and cut it in half vertically. Now I could put this half cup over each cup I'd use to mix and just draw the line on it, meaning that I didn't have to weigh out my resin each time.

To color the resin, I used red, yellow, and blue dyes made especially for it. I also made the resin slightly more opaque by adding a pea sized daub of Bondo to it before mixing. Make sure you mix your resin thoroughly before adding your catalyst. Each of my 1.5oz servings of resin would need six drops of MEKP. Be careful when using MEKP, as it burns when it contacts the skin, and is very bad for your health. Make sure to work in a well ventilated area or use a NIOSH rated respirator.

After you've mixed your resin and catalyst, you can pour your keys using the same high pour method described before. Make sure to go slowly, and to take out all the bubbles you can with a stirring stick or other small instrument.

Step 6: Demold and Admire

Since the silicone mold is very flexible, you can simply bend it until your parts fall out. Make sure to insert the little rubber bumpers in your parts before putting the guitar back together. Look here for the details on lighting up your guitar for night shredding!

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    160 Discussions


    7 years ago on Step 2

    Try putting a really tiny amount of plasticine clay at the seam where the board and the part come together. This will help secure the part to the board and keep the silicone from flowing under the part. Makes for a cleaner and sharper edge.


    10 years ago on Introduction

    Due to price of silicone and my inability to find any without ordering online (which I'd prefer not to do), could plaster of paris be used instead? Also, When I've got the LEDs in, I don't want it to be like a small light coming from the center of the button, I want the whole thing to be lit up. Would the best thing to do be make clear buttons with Bondo and colored LEDs? And finally, what's the best kind of LED to use? I don't want it to be blinding, but I want the button to be very well lit up (so almost blinding :P). I also want it to last as long as possible on a 3V battery. Thanks for the help and amazing tut!

    5 replies

    Reply 10 years ago on Introduction

    Plaster of paris would not stretch like silicon would, so you'd have a harder time getting the parts out and you might not get as good of a mold. I made totally clear buttons and colored LEDs and the whole button lights up for me. Sharpie markers work well for coloring LEDs. I used 5mm white LEDs with a recommended voltage of 3.3-3.6, but I've been running them pretty well on 3V. Bear in mind your fingers will be covering any button that is lit up, so the light will be reflected back through the button.


    Reply 10 years ago on Introduction

    OK, thanks. 2 more questions; 1. I've noticed in a picture on the LED instructable that there are little black strips on the new button. The current buttons have these on. Am I supposed to remove them and put them on the new button? 2. Where is a good place to buy LEDs, or more specifically, in Canada. Retail prefered, but online works, I guess.


    Reply 10 years ago on Introduction

    1. the black strips are removable. 2. I got mine from Radio Shack, though I don't know if they're in Canada. Their website would probably be able to ship them there.


    Reply 10 years ago on Introduction

    translucent white paint paint the inside of the key with this paint


    8 years ago on Introduction

    Can anyone give me a rough estimate as to how much the materials for this project would cost altogether?

    armored bore

    9 years ago on Step 5

    I managed to make a mold just fine, but the resin came out funny on me again. Even after letting it sit for a day, it was still very tacky. Does that mean I'm not adding enough of the catalyst?


    9 years ago on Introduction

    Well, I'm attempting a strum bar version of this mod, and it's worth noting that the mold for that part is much more difficult to manage.

    Also, for sticky parts, I'd recommend low-heat baking of the part.  It'll harden it up a bit-- just make sure you don't melt it.


    10 years ago on Introduction

    So, if i only had 3v of power coming from the battery, when two or three buttons are lit up at the same time, would they shine less bright?

    2 replies