Introduction: Elf Ears, Custom-made in Silicone Rubber

  While costume shops have been selling foam latex pointed ears for some time, their generic one-size-fits-all shape means a standard and relatively bulky set of points which can never completely blend with a human’s natural earlobes.   The extra-soft and porous nature of foam latex also means the ears are limited to a few applications before giving in to the stresses of repeated use.
  In this Instructable you will learn how to make your own custom-fit set of pointed elf ear appliances from two-part silicone rubber, a non-porous material which can be glued, applied, removed, cleaned, and reused many, many times.  I have been using the same pair for a few years now, so if you are attentive and careful, your ears could last indefinitely.

Edit:  The silicone rubber I am using here is Douglas & Sturgess brand SR-1610.  Smooth-on makes rubbers with comparable properties for their Dragon Skin line.  Use the softest mixture available, with the least amount of color.  One of the advantages of silicone is it's ability to scatter light and create a realistic flesh-like glow and be transparent enough to blend into real flesh.  

I make my ears at TechShop.

Also works for: faeries, fairies, pixies, pillywiggins, goblins, hobgoblins, demons, leprechauns, gnomes, hobbits, nymphs, naiads, sylphs, satyrs, imps, demons, orks, vulcans, romulans, werewolves, na’vi

Step 1: Aquire:

Most of these materials are available through

  -Plaster (I recommend Ultracal or another thin and extra-hard-setting mixture)
  -Silicone rubber (soft and translucent)
  -Petroleum Jelly
  -Ear plugs
  -Clay (non-drying and sulfur-free)
  -Silicone pigment or acrylic paint to match your human’s skin tone
  -Spirit gum or medical adhesive
  -A silicone-friendly release agent (here I am using Ease Release 200)
  -Foundation makeup 
  -Mixing cups and stir sticks
  -2 large clamps

Step 2: Prepping Your Human

Prep your human’s ear with the petroleum jelly and ear plugs.  Be conservative with the greasy stuff, alginate will generally not stick much by itself and residual petroleum will interfere with the silicone curing process. 
  Cut out a hole in the bottom of a cup or bowl just big enough to fit one ear through.  This will keep the alginate from running and will produce a stable and easily handled housing for the negative mold of your human’s ear.  Sit your human comfortably with their head resting on its side and have them help hold the mold housing in place.

Step 3: On the Mixing of Alginate

This part requires you to work fast because the alginate will set quickly if properly mixed.  Add the alginate powder to half a cup of water.  Mix it in and keep adding powder until it is just thick enough that it will hold some of its shape.  Begin to apply to the human’s ear by working it into the interior curves.  You do not want air bubbles forming there.
  Next, fill-in around the outside of the ear.  The alginate will run to fill-in much of the area, but you need to build a thick layer around the top and outer edge of the lobe.  Mix more alginate if necessary to create a stable mold which can hold its own shape without an ear inside.
  In 15-20 minutes alginate will set to a semi-solid gelatinous consistency which will hold fine detail but will still be very wet to the touch.

Step 4: Release the Mold!

Have your human gently pull their ear from the solid alginate.  Check for air bubbles.  If your mold is good, begin to mix the plaster right away since the alginate will shrink as it dries-out.
  Mixing plaster is a similar process to mixing alginate, except that a more thorough mixing is required for optimum results.  It is also harder to add water to a plaster mixture which is too dry.  Start with the water and gradually add plaster.  Ultracal generally works with a mixture of five parts plaster to two parts water.  The final mixture will be thin and watery to capture extremely fine details, but too much water will produce a weak casting.
  Pour the plaster into the negative mold.  Be sure to shake or tap out air bubbles, as they will ruin your casting.  The alginate is a one-time mold and you will have to destroy it to remove your plaster positive ear.  Your plaster mold should overfloweth.  Although the Ultracal will set in less than an hour, it is best to give it several hours to reach full hardness, especially with such thin shapes in the very wet negative alginate mold.

Step 5: Release the Mold (part II)

Pull the alginate mold from off the replicated plaster ear.  Only now will you be able to tell if both of your pours went right.

Step 6: Building the Elven Points

  Using a non-sulfur, non-drying clay, (sulfurous clay like Roma Plastilina will affect the curing of the final silicone rubber appliance) sculpt the two points from where they diverge from the natural shape of the ear.  Because the silicone you will be using is translucent, you will not need to create a super-thin flange for blending the edge to the human’s real ear (that would also complicate the gluing process).  Create a sharp angle but wth a well-defined edge.  Silicone is much heavier than foam latex, so be frugal with the clay and keep the part thin.  Sculpt the lower flange contacting the back of the earlobe thicker.  This will give a strong bond to the human’s ear and provide ballast to the perkiness of the elven points.

Step 7: Making the Production Mold

The complex shape of the ear makes a single-part solid mold impractical.  I have opted to pour a cast for the back part of the ear and wait for it to set, then add a release agent and pour a mold for the front half.  Your seam will be along the outer edge of the lobe, and may result in a thin flashing on the final appliance.  This is usually thin enough that it can be trimmed without leaving a visible artifact.
  Here I am adding extra clay to cover almost every bit of the plaster that is not covered by the point extension.  This will allow for an easy release of the plaster halves.  I am using Ease Release 200 and some thin sheets of aluminum foil to better demarcate the two plaster halves (a plaster mold from a plaster mold can be a tricky separation.)

Step 8: Pouring the Silicone

Once the plaster mold is completely dry, pry the two halves apart.  Remove the clay that makes up the point of the ear, and pour in the silicone rubber.  Although distributors will sell pigments in a variety of colors which can be mixed to produce skin tone, I have found acrylic paint to work just as well for flat, natural colors.  A little bit will go a long way, and you want to keep some translucently to the rubber, so start with a drop and add more if you need to.  Mix the paint into the Part A and then add Part B.  Extra additives are available to increase or decrease the viscosity of the rubber, though I have opted not to use them. 
  Silicone rubber resists sticking to most non-silicone surfaces, even porous ones like plaster.  I use a light spray of Ease Release 200.  Too much will cause a loss in definition and will give the final appliance a slick, waxy finish, which will look more like a special effect than a real earlobe.
  There is a similar issue here as with pouring the mold over the human’s natural ear.  There are many places for air bubbles to hide and not an easy way to ensure an even pour.  You must first coat every surface, the inside walls of the outer mold and the outside of the positive ear mold.  It’s okay for some to overfow, there is actually no way to avoid that.  You can trim it afterwards. 
  Put the back half of the outside mold into its place. 
  Immediately after applying a thick coat, place the front half of the outside mold on top.  Clamp the parts together and turn upside down.  If there are any air bubbles inside, this will ensure that they float to the back of the appliance where they will be less visible.

Step 9: Release Your Elven Features From Their Prison of Stone

  Remove the cured silicone parts and trim the flashing.  A well-constructed appliance will hold itself in place on a human's earlobe, without the application of glue.  An adhesive is necessary to hold down the edges and keep the ears on during a voyage to Valinor or while battling the armies of Mordor.  I use spirit gum, or the slightly higher-end medical adhesive.  Further blending and color-matching can be accomplished with a little foundation make-up.