Since I mostly referenced this instructable (https://www.instructables.com/id/LEGO-Man-Costume/) as a basis for my boyfriend's mask, I hadn't planned on posting my own instructable, but now that there is a Fandom contest and a Remix contest, I have changed my mind. For my Unikitty mask, I was able to use a simple cardboard box and some foam shapes from the floral section of Michael's.
Ah, I'm currently looking at a lot of other Lego costume instructabels and realized I also looked at this one many times: https://www.instructables.com/id/The-Lego-Movie-Lego-Costumes/
Step 1: Tools, Materials, and Planning
A hack or pull saw (only for the Benny mask)
A Dremel (also only for Benny)
A box cutter
A four foot long 12" diameter concrete form
A 2' x 4' piece of 2"-thick foam. I used the yellow kind with foil on both sides
Primer and paint
Black fabric you can see through
A box (a Sam Adams box had the perfect proportions)
Primer and paint
The first three images are my inspiration, I hope it's fine to put them here since they are not my own photos :-P.
I happened to have the right lego blocks in my room to find my dimensions. I really wanted my masks to come out as close in proportion to the actual mini-figures as I could make fit our human bodies, so I made the sketches shown above. I used 10 mm = 12 in for the spaceman mask, and 24 mm = 15 in for the unikitty mask.
Step 2: Shaping the Unikitty Mask
I took the box outside to prime it, then I worked on the Unikitty horn. I needed to take both masks to my boyfriend's place, 5 hours away, in my miata, so my goal was to make my head collapsable, since I knew his wouldn't be, and at the time I thought I would be making him a set of jetpacks also (ambitious much?). I decided to solve this problem by modifying a PVC fitting to "bolt" the box flaps together (then realized I could have used a twist tie or shoelace to get the same effect, but hey, the PVC is a little more elegant in how it fits into the unicorn horn, so boo to those simple ideas!). I drilled two perpendicular sets of holes through the threaded part of the PVC fitting, and traced and cut the arch shapes out on the flaps of the box. I cut some 1" craft foam into a 4" diameter circle, and cut 1/2" foam into a slightly bigger circle, then added a foam cone. I attached these with wood glue and covered with the wood filler for a smoother texture. The PVC fitting was just shoved into the bottom of the horn assembly for a friction fit. Sorry about the lack of horn assembly pictures, but you should see the completed horn in the later steps.
After I checked that the primer was dry on the main body of the mask, I sketched out the Unikitty angry face (obviously you could do the happy face). I used the eyebrows for my eye holes, since my eyes do not line up with hers.
One modification that this mask needs is some sort of internal structure to fit it to the width of the wearers head. I never added any, but knew I wouldn't have it on most of the night.
Step 3: Shaping the Benny Mask
The most time consuming part, was probably sawing the sections of tube, but eventually I used my Dremel to speed things up, and give my forearms a break. I used three layers to make the helmet, cutting the hole out of each layer before gluing the next in. I kept the last cylinder, for the face, separate to make painting easier.
I cut two circles from the foam to match the 12" diameter tube, to make the rounded top of the helmet. I cut and carved a hole / divot in one of these circles to hold the mask firmly on the wearer's head, a nice distance from the front of the mask. Then I glued the two discs together with spray adhesive. Next, I had a lot of fun carving the foam to make the general dome shape. I beveled the edge with a drywall knife, and then rounded the bevel with my little Ofla. But the best part was just sanding it. Before that step, you wonder if you'll ever have a nice surface, then sanding it is like instant gratification. I can't wait to make some more foam sculptures.
The one thing I would change if I did this again, is the shaping of that dome. I think the dome came out a little flat for my liking, and I wish I would have taken the curvature further. Due to my uncertainty of whether this foam would take spray-paint, and concerns regarding texture, I decided to seal the foam with wood filler. After the first coat of wood filler, I glued the dome onto the cylindrical part of the helmet. I kind of doubted this would work, but after nesting three pieces of form, the cylinder was 3/8" thick. I scored up the foil around where the glue would be applied, and laid down my bead. There were a few gaps, but I realized the surfaces made good contact with the help of putting a heavy box on top of the dome, the oldest form of clamping. Finally the ugly flat part comes in handy. Once it was done, I also flipped it over and ran more glue into the seam from the inside. I think the extra wood filler I used to smooth out this seam on the outside helped further with the connection.
I think I did two full coats of wood filler with sanding in between, and a third just to fill in some more noticeable divots. I used my Dremel to rough up the helmet like it is the movie, adding some dents and the crack in the lower portion. I had also read a tip about using glue to seal foam, so I did one final coat of wood glue, over the whole helmet, just to be safe. Then I moved on to spray painting.
Step 4: Painting and Finishing
I painted the helmet with the blue color, and the front of the face with a lego-y yellow. I used acrylic paint to color in my primed Unikitty mask and horn while the Benny helmet and face were drying.
When the Benny parts were dry, I glued the face into the helmet. Next, I came back in with glue and glued the bottom of the helmet as skewed as I could get it, to match the detail from the movie. When the helmet was done gluing, I sketched the Benny face on. Cutting the face out was very difficult and frustrating (oh, and it was 2 am, the night before Halloween...). I should have cut it out prior to painting probably. I used my Olfa knife to score the spray paint, so it wouldn't peel or crack, then I cut with a combination of that and the serrated dry-wall knife. The serrated knife probably worked the best, but I couldn't do very tight radii with it. I used a sharpie to color around the tongue, and to blacken the inner edges of the facial features. I painted the tongue red. Finally, I duct-taped black fabric to the inside to blacken-out the eyes and mouth.