I've gotten a lot of questions regarding the construction of my GLaDOS cosplay recently and rather than answer each of them individually, I figure that typing this up is faster.
For the halfmask:
I was heavily inspired by Volpin's Portal Gun tutorial, even though I wasn't making the gun. I tried to follow his process, since I knew that the finished mask had to have the same plastic-y glossy finish. However, Volpin is a crafting genius and used a lot of vague, but still very technical, mumbo-jumbo in his descriptions so I interpreted it as best I could.
Also, the foam carving and the gesso sanding is very messy and will leave dust everywhere. Don't do it indoors! I was stupid and pretty much did this entire project in my bedroom. Everything is still kinda dusty and I probably have cancer or something from breathing it in.
Step one was gathering the materials:
Medium and Fine Grit Sandpaper
Black Acrylic Paint
White Acrylic Paint- Optional
Hot Glue Gun +Sticks
Electronic Tea Candles
Tacky Glue (Elmer's would probably work as well)
I had to order the candles and the wonderflex online, everything else I could find at a generic craft store like Michael's.
Step one: Carving the foam.
This will form the core of the mask. Before this cosplay, I knew nothing about the foam, and I didn't know that there are two different kinds- Dry foam and Wet foam.
The dry foam is used with artificial flowers and is very sturdy and more like styrofoam. The wet foam is meant for live flowers, so it acts like a sponge in order to soak up water. Also, if you handle it roughly it will bruise and with enough crushing, it will crumble into dust. Of course, I bought three bricks of wet foam because I didn't know any better. It worked, but it was very temper-mental and I had to handle it gently, especially when I was carving the black eyepiece (but more on that later...)
I'm not sure whether I should recommend that you use the dry or wet. Dry would be the easier choice, but i can only provide info on how the wet behaves.
Use the X-acto knife to cut out the foam into the shape you want. The most important part is that you're constantly trying it on when you're carving so that you can match it to the shape of your face.
The mask should be in two parts- one for the white and one for the black eye piece. Carve the white first, then worry about the black. The white and the black base should fit together, but not too tightly. Once you have them carved, (if you're using wet foam) cover them in three coats of tacky glue, letting each coat dry before adding another. This will make them less fragile and they will no longer crumble and leave nasty foam dust everywhere.
Step Two: Wonderflex
Once you have a glue-tastic foam base, get ready for the Wonderflex! This was one of the only things that I had to order online. Wonderflex is a sheet of thin plastic that when heated can mold into any shape. I used a strong hairdryer to heat the plastic, even though most sites say that you need something like a paintstripper. I used a 21" x 13" sheet and barely had enough. A larger sheet would provide more room for error.
Lay the base down on the wonderflex and trace around each side (There should be 5), then cut out the wonderflex with scissors and heat it each one up at a time. Place on the the base and press down lightly until it's cooled and hard. On the seams, it's better to have a small gap than have a raised bump, since that is so much harder to smooth out.
When you're done with the wonderflex, The base should be hard and plastic-y and beginning to look more GLaDOS-like.
Step Three: Gesso hell.
This is the most time consuming part of the process. Gesso fills in the cracks and provides a way to easily sand out a smooth texture out of the mask. However, this takes FOREVER, but trust me, it will look fabulous by the end. Add several thick layers of Gesso with a paintbrush to begin with, then when they are completely dry (leave it overnight) begin sanding with medium grit sandpaper. Continue adding gesso to fill in holes and to hide seams until you can run your hand over the surface and feel no variations. If you sand down to the wonderflex in some areas, don't worry, just add another layer of gesso. After the first few layers, you don't have to wait overnight, just blast it with the hairdryer until it becomes hard enough to sand.
After it is smooth and free from imperfections, switch to fine grit sandpaper to hide the texture left behind by the medium grit. Continue sanding until you are satisfied with the texture. After this, you may choose to paint the base white, but I did not because of the bristle texture left behind by the paintbrushes.
Step Four: Shiny-ness
This step makes your pretty white texture look spectacular. Apply coats of sealant to the base, letting each completely dry before adding another, until you can see defined light reflected in the gloss.
Step Five: The eyepiece
I had to carve the eyepiece about three times before I got it to look right, but once you figure out the shapes, the rest of the process is pretty straightforward. Repeat the process and hotglue the pieces together and paint them black, but don't spray it with the sealant (GLaDOS's eyepiece isn't as glossy as the white plastic on her headpiece.) Make sure the black paint is dry before hotgluing it to the main halfmask. Once it's all assembled, take a tea candle, paint the side facing out black and hot glue it into the eyepiece hole. If you have any experience with LED's, I suppose you could disassemble the light and recontruct it in a way that takes up less space, but I don't really know anything about that.
Step Six: Attaching it
I had a broken headphone set that I planned to attach it to, but it ended up being too heavy and kept falling off my head. That's why I'm wearing a wig with ponytails even though they don't really fit GLaDOS's personality. Attached the plastic band from the headphone onto my head with the clip on ponytails, and they stayed perfectly. It was a last second fix, but I still think it worked pretty well.
For the dress: Yes, I made it myself out of White and Black Vinyl/PVC fabric (not sure what it's exactly called...) that I got from my local JoAnn Fabric's.