Plaster Positives

While rehearsal masks are quick and simple, there are better ways to work on a more elaborate mask and still have it fit specifically to one person’s face. Basically, this process involves making a negative mold of a person’s face, then using that mold to make a plaster positive. The bad part is that it’s messy, complicated, and a little intimidating for the person being “masked.” The good part is that once you do it right, you’ll have a positive face cast that you can use over and over as a base for making masks on. The process is tricky, and has a lot to do with timing. You may even have to do it more than once to get a feel of the timing needed (just make sure your partner loves you and trusts you very much, and won’t mind doing it again ^_^

  1. Materials
  2. Setting and Preparation
  3. Step 1 – Prepare the Subject
  4. Step 2 – Mix Alginate
  5. Steps 2 continued – Mix Plaster
  6. Steps 3 and 4 – Alginate and Cheesecloth
  7. Step 5 – Cover face with Plaster
  8. Step 6 – Remove Mold from Face
  9. Alginate Negative
  10. Step 8 – Plug Holes and Mix Plaster
  11. Step 9 – Spray Mold with Oil Soap
  12. Step 10 – Pour in Plaster
  13. Final Steps



  • A quiet workspace where things can get messy without a problem
  • A table for the person being molded to lay on
  • Alginate (as seen in the photo), this is a casting material used by dentists to take molds of people’s teeth. Thus, it is non-toxic, and is removed pretty easily, so there is no need to vasoline one’s face. We use this because it takes such an accurate mold, but since it is so floppy, we need plaster to support it.
  • Pottery Plaster
  • Several buckets for mixing
  • Towels (which will be ruined) or old T-shirts
  • Vasoline
  • Drinking straws (optional)
  • Cheese cloth or large pieces of gauze
  • A headband (to cover ears and keep hair out of the way)
  • Clay, or some similar material to plug up holes in the mold and support it
  • Murphy Oil Soap


Setting and Preparation

A note about setting:
Unlike the rehearsal mask process, which is quick and fun, this process is a little intimidating. The person will have their entire face covered in plaster, will be breathing through straws stuck up their nose, and will be blind, deaf, mute, and probably feeling somewhat vulnerable. Thus, to make things as comfortable as possible, set up your work place in a quiet area that will not be likely to have visitors. If people come by during the process, ask them to be as quiet as possible. Also, be sure and tell the person every thing you’re doing before you do it, and warn them in advance when you’ll be splattering stuff on their face.

It is helpful to have two or more people assisting in this process, as a lot of it depends on timing as far as the mixing of the alginate and the plaster. It can be done with one person, but it certainly is easier with more.

Cut up strips of paper towels–both for bordering the person’s face and for cleanup, and cut pieces of cheesecloth to have ready.

Have your partner (the person being masked) dress in old clothes they don’t mind getting messy. Also, no make-up, especially lipstick or lip gloss (the alginate will slide off the lips if there is lipstick on them, this is also the reason we do not lather our faces with vasoline this time, the alginate comes off very easily so we don’t need it anyway). Have them put on a head band to keep their hair out of the way and cover up their ears (in spite of precautions, the alginate is runny, and having it drip in your ears is uncomfortable)

Make sure you have all your materials ready, and have a good idea of the process to make sure everything goes smoothly.

Step 1 – Prepare the Subject

– Prepare your partner. Have them lay on top of a worktable, so you can work easily above them.

– Give them a t-shirt or towel to use as a pillow, then wrap another towel around their face, covering up the ears.

– As with the rehearsal masks, fold a paper towel in half and dip it in water, then smooth it against the side of their face. It is helpful to use vasoline to help stick the paper towels to the face. This process is very messy, but do your best to make it tolerable ^_^

– NOTE:  These photos shoe the subject with straws to put in their nose for breathing.  This is actually quite dangerous, as if something were to jam the straw when the plaster is on and the subject were to start bleeding, it could be very bad.  So, use breathing straws at your own risk. 

Step 2 – Mix Alginate

– Mix the Alginate by dumping it a bit at a time into warm water, mix it up with your hand.

– Warm water makes the alginate set faster (it is also more comfortable to apply to your partner).

– Although the alginate sets faster than plaster, it takes longer to mix. Timing is important, this is where it is helpful to have another person, so they can be mixing up the plaster while you mix up the alginate. 

Steps 2 continued – Mix Plaster

– If you can have someone else mix up some plaster for you at this time, it is very helpful. Here’s a quick run-down if you’ve never mixed plaster before…

– Start with room temperature water in a small bucket or container, you don’t need a lot of water at all, maybe an inch up from the bottom.

– Start sifting the plaster into the water. DON’T MIX IT YET! Keep pouring in plaster, making sure you pour it all around the interior of the bucket, not just one spot.

– When the plaster starts to sit on top of the water, and almost all the water is covered up by plaster, you may mix. Squish it up with your hands, making sure to squeeze out all the lumps (after you’ve started mixing, don’t add any more water. If you don’t have enough, you can always make another batch) 

Steps 3 and 4 – Alginate and Cheesecloth

Step 3:
– The alginate should be at a somewhat gooey consistency, similar to cake batter.

– Give your partner fair warning. Have them close their eyes and ready their straws, and be sure you let them know where you’re pouring first.

– Start ladling on the alginate with your hands. It will be somewhat runny, but try to cover the entire face. Let it drop over their nose between the straws, and make sure any bare spots are covered.

Step 4:(sorry I have no photo of this, both hands were needed for this process)
– After you’ve covered your partner’s face with the alginate, cover their face with cheesecloth and gently apply pressure, to make sure the alginate adheres to the cheesecloth.

– Be sure the entire face is covered, the cheesecloth will act as a link between the alginate and the plaster, so don’t forget this step!


Step 5 – Cover face with Plaster

– Ideally, at this point, the plaster you mixed should be the consistency of whipped cream. If it is still too runny, just wait for it to set a little bit. It’s better to have to wait on the plaster to set slightly than rush through the alginate step because you mixed the plaster too early.

– Start applying the plaster to the face, smoothing it into the cheesecloth at first, then layering it on. It has the same feel as icing a cake ^_^

– Don’t forget to get around the nose and between the straws. At this point, your partner can probably let go of the straws and they will hold in their position.  I would actually recommend removing the straws altogether once the plaster sets enough that it wouldn’t drip into the nose

– Let the plaster set up (it will start to get warm when it was setting) for 5-10 minutes. You can use this waiting time to clean up. 

Step 6 – Remove Mold from Face

– Removing the mask can be tricky,, so be sure and explain what to do to your partner so they understand.

– After the plaster has set, gently help your partner up into a sitting position, keeping one hand on the mold

– Have your partner take hold of the plaster mold and lean forward, as if they were looking at their knees.

– Have your partner carefully slide the mold away and down (with the direction of the straws, so they don’t impale themselves in the nose) to remove it from their face. 





Alginate Negative

Now you can see the negative mold of the person’s face.  

The next steps should be followed up right away.


If you let the alginate dry for too long (like over an hour) it begins to shrink, and it won’t match the person’s face exactly anymore.






Step 8 – Plug Holes and Mix Plaster

– Now take the clay (or whatever you have available) and plug up the holes from the straws

– Use the clay and/or other supports to hold the mold in place. Make sure it’s sturdy, but not so much that you can’t tilt it or move it to adjust for plaster being poured into it.

– While you’re doing this, you can have your helper start mixing up a second batch of plaster, although there isn’t as much of a time pressure now. 



Step 9 – Spray Mold with Oil Soap

Right before you’re ready to pour the plaster into the mold, spray it down with murphey’s oil soap.  

This just really helps when it comes time to pry the plaster positive away from the mold, it makes things really easy.


Step 10 – Pour in Plaster

– Pour the plaster into the mold, watch out for leaks, and tilt or move the mold accordingly.

– Let it set for at least an hour or so 

Final Steps

– When the plaster is set, pry the positive away from the mold. You may have to chip off some places where the two sets of plaster touched each other, but the oil soap and the alginate should make the two pieces come apart very easily

– Now you have a positive of your partner’s face! You can sand out any bumps if you need to, but minor flaws should be no problem, as long as you have the main bone structure of the face. Now you can build off of this positive, making masks specially suited to your partner’s face, without needing them to lay as a dummy.

Game Designer