Work in Progress: A Dragon's Eyes (part 1)

The image from the catalogue.

From time to time I get requests.  Bizarre requests in some cases.  Recently a friend of mine contacted me with a project.  An odd project.  He and his wife were planning to upgrade their mailbox.  They had purchased a resin dragon from a mail-order company that specializes in fantasy and sci-fi themed home decor.  Standing about four feet tall on its hind legs the dragon has a hollow, square-shaped void all the way through the longest part of its body (feet to head).  The hole is just large enough to accommodate a 4X4 post (sunk into the ground of course) which acts both as an anchor and as the mount for the mailbox.  The mailbox itself rests on the top of the dragon's head (I think it would be cooler if the box was in the dragon's mouth, but I didn't design the thing).



Dean (my friend) had examined the decoration when it arrived, and he discovered that in addition to the long, hollow core there was also a fairly large void inside the dragon's head that's accessible from inside the 4X4 core.  It's more than adequate he realized to contain some electronics for some kind of practical effect.  Dean is a software developer and brewmaster (it's a long story) not a weird-ass projects developer, so as one of the weirdest people he knows naturally he called me (actually he'd seen another project I'd completed that's similar to what he wanted done here).

The idea he and his wife had and presented to me was to cut out the opaque resin eyes of the dragon with a rotary tool and replace them with super-bright LEDs.  They initially wanted to power the lights from a battery that recharged daily via a solar cell (kind of like those garden stake-lights you can find at almost any hardware or garden store), but the location of the existing mailbox in the shade of a large tree made that difficult.  Instead Dean suggested running a wire from an existing 24 volt power supply (for a koi pond in their front yard).  It sounded like fun, so after a short brainstorming session to discuss possibilities I drove to his house to see the dragon for myself.

The device Dean had seen previously that had inspired him to bring me in on this project was a pair of steampunk goggles I'd made for my wife.  I had hand-sewn the goggles entirely out of leather and used thick Plexiglas lenses.  The lenses I had etched and frosted to resemble a cat's eyes (slit pupils), and I had edge-lit the lenses with a pair of bright, green LEDs (concealed by the leather rim).  The effect is quite vibrant.  Everywhere the lens is etched or frosted the light of the LEDs is refracted out of the acrylic and visible to viewers nearby.  Everywhere the surface is undamaged the light isn't visible, and the surface appears dark.  The deeper scratches of the etching grab more light and are therefore brighter than the shallower scratches of the frosted areas (which I created by abrading the surface with coarse sandpaper).  The goggles actually put out enough light to see by in the dark, but the same amount of light goes in both directions making it impossible to see in the dark if you're wearing them (they're just a costume piece anyway).  It was something along these lines that Dean and Adrienne wanted for their dragon.

The goggles, turned on.  The batteries and wires are concealed inside the eyes.

Since we didn't have an exact plan for what we were going to do we didn't want to start by damaging the original resin sculpture.  I wanted to have a cheap duplicate I could carve up, and that meant making a mold of the original.  I've experimented with mold-making a couple times using latex.  It's a long, painstaking process of painting on layer after layer of liquid latex and letting it dry between layers before the mold is finally thick enough to survive being removed.  A much quicker option is two-part pourable silicone available at our local hobby and craft store.  I've played with that before as well, but pourable silicone mold material is fairly expensive.  A third option I've been wanting to try that has become popular in the maker community in the last year or so for making rubber parts:  Oogru.

Silicone caulk (silicone I) is an inexpensive and commonly available gel.  It's available at any hardware store for sealing windows and doors.  In thin layers it hardens quickly to form a flexible, water-tight seal.  In large quantities, such as squirting a bunch into a cup, only the outside layer hardens forming a "skin" while everything on the inside of the mass remains liquid for a very long time.  The reason for this is that silicone caulk requires moisture from the air in order to harden.  When the outside layer cures it effectively blocks any additional moisture from getting to the inside.  Some very clever individual discovered that if you mix common corn starch (available at any grocery store) with common silicone caulk (in nearly equal parts) moisture from the cornstarch (which is hygroscopic meaning it naturally and constantly absorbs water from the atmosphere) diffuses slowly and evenly into the silicone allowing it to cure throughout all at the same time.  Mixed quickly and in equal parts the caulk remains a workable liquid with the consistency of cold cake frosting for about five minutes. 

Oogru (the silicone caulk/cornstarch mixture) releases acetic acid as it cures producing some pretty potent fumes.  It isn't really harmful (acetic acid is basically vinegar), but it can cause respiratory irritation (use only in well ventilated areas) and possibly skin irritation if it's applied to the skin.  Don't use oogru to make molds of body parts!

I brought all the requisite materials with me and set to work making a mold of the dragon's face and eyes.  I coated the surface of the resin with silicone lubricant so the mold wouldn't stick too tenaciously.  I applied the oogru in two layers: the first layer thinner than the second in an attempt to get as much detail as possible.  After the oogru had completely cured I mixed some plaster and soaked a piece of cloth in it, and I wrapped the plaster-impregnated cloth over the oogru mold to form a mother-mold.  A mother-mold is essential when working with a flexible primary mold.  When the primary mold is removed from the original there is nothing holding the shape of the mold, so reproductions from the mold will never be exactly like the original.  A rigid mother-mold acts as a shell holding the flexible primary mold in its original shape once its removed from the original allowing for more accurate reproductions.

The mold on the right and the reproduction on the left.
Not too bad for my first attempt, if I do say so myself.

The next day I started making reproductions from the mold.  I used two-part, pourable polyurethane resin (available at our hobby and craft store under the brand name Alumalite) in small batches.  I began by brushing the liquid resin into the mold only to discover that it cured VERY quickly and almost incorporated the brush into the finished product.  I switched to even smaller batches (10 ml or less at a time), poured it into the mold, and kept rocking the mold until the resin cured.  (At one point I got distracted and accidentally poured some of the resin onto the leg of my jeans ruining them instantly and gluing my leg hairs to the inside of the pants.  That made for an exciting next few minutes)  This was effective for the recessed features of the mold (the valleys), but it left the projections (the hills) dangerously thin.  As I worked with it I noticed that the resin became increasingly viscous as it cured.  I experimented with the resin until I could consistently get it into the mold at a high viscosity and work it into position over the projections with a popsicle stick just as it became too hard to manipulate.  In this way I was able to make the resin thick enough to survive unmolding.

This is the side of the reproduction up close.  Notice the pronounced curvature of the eye.

 In my next post:  Creating a complex eye.