Introduction: Latex Mask Part 2: Molding the Sculpt and Casting Latex

About: I've been making movies as a hobby for nearly 8 years now, and I've always enjoyed the fantastical and imaginative. I occasionally take on the challenge of trying to construct some recreations.
This is part 2 of an Instructable which will show you how to make a latex mask. In Part 1, we made a 2-part plaster mold of our head and used it to make a clay copy. Now, we will be taking the clay sculpture, molding it with plaster, then pouring liquid latex inside of the mold, and pulling out the final mask.

Normally, molding a sculpt can be difficult, but this method is somewhat simple and easy. Usually, molds of mask sculptures are done as 2-part molds. For simplicity's sake, I'm doing it all in one piece. It is generally easier to do it all at once instead of in halves, but the method does have its disadvantages as well. I'll point those out along the way.

And, as always, we'll try not to spend too much money. You'll have to make a mess, though, and the process will take some time: a few hours to make and clean the plaster mold, and several hours more for casting the latex.

Here's a video tutorial you can follow, or watch as an introduction to the overall process, including both Part 1 and Part 2. The step-by-step Instructables are more detailed and have more advanced tips and recommendations.

Step 1: Materials Needed

Materials needed for making the plaster mold:
  •     Clear Spray Paint/Lacquer
  •     Plaster of Paris, water, and a bucket
  •     Plaster Strips
Materials needed for casting the latex:
  •     Liquid Latex
  •     Hair Dryer
  •     Baby Powder
Other tools you might use would be a paintbrush, scissors, wires, toothbrush, wash towels, sandpaper, and acrylic paint. And you'll definitely want a tarp, or to lay down newspapers over your working area.

Total cost of materials (not including materials I already had lying around) was about $6 of plaster. A craft store or hardware store would be the place to find the plaster of Paris (be sure to take advantage of the usual "40% off one item" coupons at craft stores). Plaster strips are good to buy in bulk, from Amazon or eBay, or another online store. A good price is around $50 for a 20 pound box. Liquid latex is best to buy online, in gallon-sized jugs. Check eBay or costume/makeup supplies websites. Do NOT use Mold Builder. It's not safe on skin. Make sure your latex is specifically for mask making. Usually priced around $50 a gallon.

Step 2: Sculpting the Design

I nearly skipped over this step, didn't I? Why would I show you how to make a clay head, and not show you how to sculpt the mask design? Well, I'm simply not qualified for that. I don't have much training or background with sculpting. All I do is try to make the form as best as I can. I watched a lot of YouTube videos for reference, and tried to use tools and methods that others had used. This video shows good close-ups and tips for technique.

My design was a Batman mask based off of The Dark Knight. It's a simple enough design, but very difficult to refine. Making the sculpt smooth was the greatest challenge. Using some rubbing alcohol did help to soften the clay. I used many tools, and followed a lot of reference pictures, but didn't want to take too much time doing this, so I sculpted until I was satisfied. It could be a lot better, especially if I'd taken more time. This was only about 2 hours worth of work. But for an experimental molding and casting process, I didn't even know if it would be worth it to make a perfect sculpt.

Here's a time-lapse of my sculpting process:

Reminders about clay:
There's a large variety of clay to choose from. My attitude is; whatever is cheap and gets the job done. For me, that ended up being a 25 pound box of pottery clay for $10. It was alright, but maybe a bit too wet and soft. Oil-based clay is better for sculpting, but more expensive. It would be good to have a layer of higher quality clay on the surface to work with.

Step 3: Covering the Sculpt With Plaster

Start off by sealing your sculpt with a clear spray paint, or a lacquer. This will seal the clay, and make it much easier to remove from the plaster mold. Wait for it to dry before proceeding.

Notes about plaster:
I'm using plaster of Paris for its low cost and ease of access. It can be a little "soft", and not too durable for detailed work like this. A stronger plaster like hydrocal is usually used for this process. If you can afford the cost, go for this higher quality plaster. But for cheap DIY projects, plaster of Paris should work just fine.

Mix some plaster with water to a thin consistency and brush some of this onto the sculpt, ensuring to completely cover small details, like wrinkles or ridges. This is called a beauty coat. We cover these delicate details first to make sure they are properly transferred to the mold. After that, you can mix a thicker batch of plaster and spread it all over the mold. I just used my hands. Tap the head a bit to get some air bubbles out.

To get more plaster under the chin, wait until most of the plaster is somewhat dried, and then turn the head upside down and cover the lower parts of the head. You'll want at least 1/2 inch of plaster covering the whole sculpt on the first layer.

To build up the mold, I used alternating layers of plaster and plaster strips; I'd lay on a layer of plaster, and then add a layer or two of plaster strips. I knew that plaster can be fragile by itself, and so these plaster strips were a good way to add durability to the mold. Add more plaster, then more strips. Repeat. I did this until the mold was over 1 inch thick. Then let it dry, for at least an hour or two.

When disposing of excess plaster, do NOT pour it down the sink; it can harden and clog the piping.

Step 4: Clean Out the Mold

After the mold is dry, we need to empty it out. Start by removing the Stryofoam head. If you cut it into pieces, like I showed here, then this will be very easy.  Then dig out the clay. Most of it should come out in one piece. Some will be left behind, especially clogged in small cavities, like my bat-ears and eye details. Use any number of tools to clean this all out; sponges, toothbrushes, sandpaper, etc. Small pieces of bent wire can help to dig into small areas, just be careful not to scratch the plaster surface too much.

It's a good idea to smooth out any imperfections in the mold. Use sandpaper to smooth down areas that aren't smooth enough. You can fill in holes or damaged areas with clay, or I found that joint compound worked very well for this.

Getting all of the tiny plaster and clay pieces out of the mold was fairly difficult. I took the mold outside and sprayed it out with water from the garden hose. Then I tried my best to gently clean the insides with a towel. I then sprayed it with a clear lacquer to seal and hopefully "smooth" the inside more.

After trying to clean this mold and get it ready for casting, I definitely understand why molding is usually done in halves as a two-part mold. It would be much easier to clean and smooth two wide-open molds.

Step 5: Cast the Latex

Set up in a well-ventilated area; a garage, or outside in the fresh air. A respirator is highly recommended for protection. Have your latex in a container ready to pour. If you want latex of a specific color, mix in some acrylic paint. The color of the latex will be darker once it dries; let a small amount of latex dry so you can see what the final color would be. Thin the latex down with a little bit of water, maybe a tablespoon or two of water per cup of latex. This will allow the latex to seep into small details more easily, and also help the layers to dry faster. You'll be casting several layers, so a quicker dry time is nice to work with.

With your latex mixed, pour a good amount into the mold. Swish the latex around to get all of the inside surface coated. Then, hold the mold upside down to drain out most of the excess. Set the mold on the ground, under some newspaper, with the hole facing down. This will help the latex drain out even more. Rotate the mold 90 degrees every 5 minutes, so that the runoff drains at the back, front, and sides of the mold. This will help prevent the latex from pooling up anywhere in the mold.

After all the excess is drained, set the mold down with the hole facing up, and let the latex dry completely. A hair dryer, on the lowest heat setting, aimed inside of the mold will speed up the drying process. With a hair dryer, it should only take an hour or so for the layer to dry.

Pour in more latex, and repeat the process. Do this for about 4 or 5 layers.

Step 6: Pull Out the Mask and Finishing

After all the latex is dry, we're ready for the most fun part of the process. Sprinkle some baby powder onto the latex; this will prevent the latex from sticking to itself. Peel the latex away at the edges of the mold, and slowly pull it away from the plaster. Be gentle with it, don't pull too hard. Add more baby powder to the top side of the latex as you peel it off.

Eventually, you'll have it all pulled out, and you'll have a mask!  But you're not quite done yet. Beyond cutting out eye and mouth holes, you'll probably have to clean off debris, smooth out some areas, add paint, etc. Latex mixed with acrylic paint is usually the best way to paint. For my mask, I took more latex thinned with water, and used a cheap air brush to brush on a thin top layer. This worked well to cover all the imperfections and debris, and helped to smooth out the surface. I've heard that using a dremel tool with a soft buffer bit can help to "sand off" some unwanted raised areas. For repairing major recessed areas, I've read about mixing latex with pieces of toilet paper or cloth and adding that to fill in those areas. Ultimately, your final mask will only be as smooth and well-shaped as your mold was. All the more reason to get it right the first time.

Step 7: Final Thoughts and Advice

This was the first time I'd ever done a process like this. It's not perfect, and I'm sure it could be improved upon, but it did work, and so it should work for others. I'd love to have a go at a two-part mold next time. This is what I learned, and could be good advice for future attempts:
  • Take time on the sculpt to make it as good as possible. The better the sculpt, the better the mold, and ultimately, the better the mask.
  • Cleaning out the mold is critical. Any small pieces of plaster or cracks will transfer into your mask. Not fun to try and fix after the fact.
  • If you're going to be doing this a fair number of times, a respirator is highly recommended for protection.
  • Hair dryers are my new best friend. Such a time-saver.
  • Thinning down the latex with water was critical. I did my first cast with regular latex, and the ears got clogged and didn't dry all the way, and ended up misshapen. Thinned latex preserves details and dries more evenly.
  • Again, I stress the importance of cleaning up the mask after it's pulled out. Right out of the mold, it is fairly dirty and ugly.
  • Feel free to adjust or modify any step. My method is by no means perfect. It is what works for the way I made my latex mask. Learn from others, do it cheap, and have fun!