Chapter 5
Casting and Molding
The poor incandescent light bulb, the very symbol of having a bright idea, is endangered. It’s being phased out all around the world: first in Brazil and Venezuela in 2005, then in the European Union in 2009, and now in the United States. Granted, efficient CFL and LED lights produce more light with far less energy but they’re just not as much fun. The light bulb in the E-Z-Make Oven creates enough heat to shrink plastic, harden polymer clay, fuse enameling powders, and make wiggly creations by “cooking” plastisol. So, have your own aha moment and build this light bulb–powered craft oven—while you can!
E-Z-Make Oven
The E-Z-Make Oven design is super simple: a light bulb in a can. Holes in the bottom serve as cool air intake and are also used for mounting the insulated feet and bulb socket. A grid of holes in the lid allows the hot air to rise up around the molds. An inverted pan serves as a cover to hold in the heat. The oven reaches about 300ºF with a 75W spotlight. That’s just enough to do several different kinds of heat-activated crafts: harden polymer clay, cure plastisol, shrink plastic, and fuse low-temperature enamels.
1. Lay Out the Holes
For the holes in the lid, find the center, and then use the compass to scribe a circle with a 5⁄8″ radius. Use the compass set at that radius to mark off six holes and center punch each of them. Repeat with 1″ and 1½″ radius circles. Exact spacing isn’t critical, but you’ll want a regular distribution of holes for even heat flow in the center of the lid.
Lay out the holes in the bottom of the can following the diagram.
Set the compass to the radius of the can, then use the compass to mark off distances around the rim to locate three equidistant holes for the feet. At each location, mark a spot ½″ inside the rim and center punch each spot.
Place the lamp socket in the center and mark the locations of the mounting holes. Center punch them. (If your socket has a single screw mount in the center, mark and punch a center hole instead.)
Lastly, set the compass for half the can’s radius, scribe a circle, and mark off four equidistant ½″ holes and center punch them.
2. Drill the Holes
In the bottom of the can, drill three 1⁄8″ holes for the feet, four ½″ holes for venting, and holes to fit the small bolts for mounting your lamp socket. Drill the grid of holes in the lid. Debur the holes as needed.
3. Mount the Hardware
Cut two synthetic corks in half and drill a 1⁄8″ pilot hole in three of the halves. Attach the three half cork feet using small screws pushed out from inside the can.
Insert the grommet in one of the four ½″ holes and thread the lamp cord through it. Tie a knot in the cord 6″ from the end, then split and strip the wires. Connect the wires to the socket.
Bolt the lamp socket to the inside bottom of the can using the bolts and nuts.
Install the in-line switch on the cord, 12″ from the can, following the directions from your switch.
Finally, strip the other end and attach the wires to the AC plug. For a polarized two-prong plug, the narrow (hot) blade goes to the center (hot) contact on the socket. For a three-prong grounded plug, the bare or green wire goes to the green ground contact on the socket, if any.
Screw in the bulb and test.
4. Make the Cover
Invert an aluminum-foil loaf pan and attach a synthetic cork to the outside. Drill a 1⁄8″ pilot hole in the cork and fasten to the pan with a screw.
Custom-shaped Metal Casting Mold
Unlike thermoplastics that can be melted and remolded, molding with thermoset materials is like making a hard-boiled egg: once cooked, its form is permanently set. Plastisol starts out as a creamy liquid that cures into a soft, pliant plastic. Baby Boomers might remember Mattel’s Thingmaker toy, which came with die-cast zinc molds. (See Chapter 4.) You can make your own custom-shaped molds out of easy-to-form aluminum.
The form is a hard “positive” pattern over which you’ll stretch and shape the aluminum sheet to make a “negative” mold. Make your form by sculpting soft polymer clay, then fire the clay until firm using the E-Z-Make Oven.
1. Sculpt the Form
Cut a piece of hardboard on which to make your form. Knead a small quantity of polymer clay until pliant and then sculpt your shape. Keep in mind that you’ll be stretching and deforming the aluminum over your form, so keep your shape rather shallow (the aluminum sheet will only stretch so far) and allow plenty of draft (angled sides without undercuts). You’ll be amazed at the small details that the foil will pick up. This example shows what happens when you burnish the foil over a penny!
Here I’m making a mold for casting moustaches. Roll the clay into a teardrop, then place it on the hardboard. Cut in half lengthwise with a thin piece of metal or a knife, shape the curl, and add two bits to make nose pinchers. Lastly, sculpt in some hair detail. Take some time to make small features and textures in your polyclay form.
When your polyclay form is finished, bake it in an oven set to 275ºF for about 20 minutes or until hard. Probe gently with a toothpick: when the clay springs back, it’s done.
You can also fire your polyclay using the E-Z-Make Oven you just built. It gets hot enough, but it will take more time than using a big kitchen oven. Place the lid on top of the form to keep in the heat.
When it’s done, set your firm form aside to cool.
2. Tool the Mold
The material used for the mold must have three properties: a low specific heat (to efficiently conduct the light bulb’s limited heat to the plastisol), to be soft and easily formed, and compatibility with the plastisol’s chemistry. Steel is too hard, copper is not chemically compatible, but aluminum has all three attributes. Get some 0.005″ thickness tooling aluminum from an art supply store. It’s specially made to be soft and is easily worked with wooden tools. You can also use pieces cut from a disposable aluminum pan. It’s a little stiffer and harder to form, but will work fine.
Cut a piece of foil somewhat larger than your form.
Lay the sheet over the form and press the foil around the form with your fingers. A few wrinkles and folds are inevitable, but you’ll work them smooth later.
Make some tools from wooden dowels of various diameters. Leave one end flat and make radiused tips on the other end in various sizes from gently rounded to pencil-point sharp.
Use the wooden tools very carefully to press the foil closer to the form. Don’t try to stretch the foil all at once: be careful not to tear it or poke a hole. Instead, work slowly from the sides or top toward the center of a valley or crease. Start with the roundest tipped tools first. Do a little at a time. Slowly approximate the shape, stretching the foil as you go. Easy does it! This may take some practice until you get the hang of it.
Once you have defined the basic shape, go back with a finer-pointed wooden dowel and work the small details. Firm-but-gentle pressure gives the best result. Often, as you get to the deepest part of the form, the foil will be very thin and tear easily. No worries: your mold may still be quite usable, since you don’t fill the mold up to the very top. Keep working!
Use the flat end or the side of a dowel to smooth out any wrinkles and make a flat surface surrounding your mold shape. Finally, fold down two sides to make legs so the inverted mold stands level.
Cast Plastisol Parts
A good source for bulk plastisol and pigments is Industrial Arts Supply Company (IASCO-TESCO.com). Get formulation #16 for nicely soft and rubbery molded parts. You can also get pre-colored ready-to-use “goop” in squeeze bottles from Patti-Goop on Amazon or eBay. I’ve even used old bottles of Mattel’s original Thingmaker Goop—it still worked after 50 years. Now, that’s swell!
Place the mold on the oven and add the cover to preheat. Fill a squeeze bottle with plastisol and pigment and mix thoroughly. Fill the mold by squeezing plastisol in slowly and letting it fill from bottom to top to avoid trapping any bubbles.
You can even “paint” your part by using different colors: let one color set before adding another or pour together to get a swirl effect. Place the lid over the mold to help trap the heat.
Thin shapes cure quickly; deep shapes take more time. Probe with a toothpick: when the plastisol is firm, it’s done. Carefully remove with tongs or tweezers (it’s hot!) and let cool.
When cool, use a toothpick to carefully pick at an edge, then lift and peel your part out of the mold. If you’re careful you can cast many parts from the same mold.
Faux Enamel Trinkets
Use the E-Z-Make Oven to create fun faux jewelry and trinkets! This project features colored powders that melt and fuse at low temperatures to give a bright, shiny finish. They look like glass enamel or cloisonné but you can bake it with just a light bulb. Find the fusing powders in craft stores or online. Embossing powders sold for stamping will work, too.
1. Make a Metal Shape
Cut a small disc or any other shape out of brass and debur the edges with sandpaper. Make a mark with a center punch and drill with a 1⁄8″ drill bit to make a hole near the rim. Clean the brass with vinegar and water to remove any finger oil so that the powders will adhere uniformly. Keep it clean: only handle the trinket by the edges as you go.
2. Add Powders and Fuse
Sprinkle on some low-temperature powder and build up an even layer about 1⁄32″ thick. Then carefully place the trinket on the warmed E-Z-Make Oven. After a few minutes when the powder melts and gets shiny, remove it and let it cool. You can add more powders in different colors to create a design.
I made this Jolly Hacker medallion with hand-cut stencils of thin cardstock. You could also make super-intricate, laser-cut stencils. When all your colors have been added, return the trinket to the oven for a 20-minute final bake for maximum hardness (about 300ºF in a kitchen oven).
Add a chain to finish your medallion, or glue on a pin back to make a brooch or badge.
Custom TiddlyShrinks
Here’s something else you can do with your E-Z-Make Oven: shrink plastic to make customized tiddlywinks.
Tiddlywinks is played with a set of small, color-coded discs. Use your squidger (a large plastic disc or shape) to press down and scrape across the top surface of a wink (a small disc). When you snap its edge, the wink flips up into the air. With a little practice you can aim your wink to land into the target cup.
Create your own custom squidgers and winks using shrink film. (The shrinking film is sold under the Shrinky Dink® name or as a similar generic brand at hobby stores.)
1. Make Your Image.
Draw and color your own design with permanent markers. It’s easy to copy your favorite design: place the clear film on top of the original and trace. Or create your design on the computer and use the special shrink film made for ink-jet printing. Just remember, your design will shrink in size by about one half!
2. Cut It Out.
Then cut the shapes out with scissors or a hobby knife. You can also use paper punches to make shaped holes. Be sure to completely cut out your final shape: once the plastic shrinks it will be too thick and tough to cut!
3. Shrink!
Shrink the plastic using your light bulb–powered E-Z-Make Oven. (You can also bake in your kitchen oven at 325° or use a heat gun.) As the thin polystyrene film shrinks, its thickness swells to 1⁄16″. Heat slowly and evenly to prevent curling. When it’s cool, you’ll have tough, strong plastic winks and squidgers of your own design in high detail!
4. Play!
Set up a tiddlywink course with a shallow target cup on a piece of felt or tablecloth. Play a round of “tiddlywink golf:” how many tiddles will it take to get your wink into the cup? What is the farthest distance away you can be and still get your wink into the cup on one shot? Look online for many variations and strategies in tiddlywinks game play. Try for a squop (landing your wink on another player’s wink, freezing it from play) but don’t scrunge (bouncing out of the target cup—oops!).
The sky’s the limit for your own custom tiddlywink graphics and themes: sports, movies, comic books—or mash them up. When you make your own you’re not limited to the official licensed versions: Star Wars Angry Bird Basketball tiddlywinks, anyone?
Guitar Amp Bulletin Board
This project uses two different kinds of casting: flexible room temperature vulcanizing (RTV) mold making and hard resin cast parts.
Sometimes the leftovers from one project can be an inspiration for something else. I had an odd piece of vintage speaker cloth that was too small to use on an amp but too cool to throw away . . . hmmm . . . how about using it to make a mini “guitar amp” bulletin board?
To give it a cool look like the front of a guitar amp, I made a framed tray with quarter round wood on a piece of plywood. For the look of Tolex guitar amp covering, I covered the frame with textured black vinyl upholstery material and attached it to the tray with contact cement.
For the bulletin board, I cut some masonite to make a thin backer board to fit inside the frame. I used staples around the back to fasten the speaker cloth around the board.
I lifted some Fender amplifier script art for a real retro look and printed and mounted it on another strip of thin board. This served as the “control panel” storage for the “knob” pins.
Here’s the casting part: the things that look exactly like guitar amp knobs are really pushpins! I used RTV silicone to make a mold around an actual knob, then cast acrylic to make perfect copies.
RTV is a kind of silicone rubber. When mixed with a catalyst, it hardens from a thick syrup into a firm but flexible rubber. I placed an actual knob face up in a small mold tray and poured the RTV on top. I removed the knob after the rubber had set. You can see the mold has captured every tiny detail from the numbers to the ridges and recesses.
To cast the knobs, I mixed up some polyester resin with MEK catalyst and carefully poured it into the RTV mold. I tapped the mold to release any bubbles. Then I pushed a pin through a small piece of cardboard and placed it upside down over the mold, suspending the pin in the uncured resin.
Later I unmolded the cured knob and sprayed it with black paint. I wiped it with white paint to fill in the engraved number markings. I painted the center recess of the knob with silver paint. This made a perfect copy of the original knob!
I drilled some small holes for the knob pins in the control panel. Looks just like a real amp!
I finished it off with a working pilot light by wiring a micro switch on the back of a button battery holder and wired it with a super-bright red LED. I used a cap from a tube of lip balm as a bezel. When you press the pilot light pin into the board, it glows red. Rock on!
You can do a lot with RTV rubber molds—they’re so flexible! I’ve used them to make molds from all kinds of found objects and cast different materials from resin to chocolate to Sculpey. The inherent flexible rubbery property of the silicone means it will flex away from any undercuts in the original shape and in the part you cast when you unmold. It’s also very durable and with care you should be able to get many parts out of an RTV silicone mold. For more details on using RTV silicone and polyester resin, consult the instructions that come with each.
Edible Optics
Gelatin is used in lots of things like food and candy, and pharmaceutical and paintball capsules, but it also has interesting optical properties. Fun fact: Before the advent of plastics, gelatin was used to make colorful filters for theatrical lighting and photography, and these filters are still called gels today. A fun way to play with gelatin optics is to cast lenses.
Find a cup or bowl with a smooth curved inside to use as a mold. If you have any chemistry equipment, a concave watch glass makes a perfect lens mold. You also can make a convex lens mold by stretching plastic wrap over the mouth of a glass and then sucking out the air before quickly sealing the wrap. The stretched film will make a wrinkle-free concave shape. Add a rubber band around the rim to keep it sealed airtight.
Mix up some gelatin and leave to set in the mold. Mix the gelatin in a very concentrated form, about 1Tbsp of powdered gelatin in 1⁄8 cup of hot water. Stir until dissolved.
Pour the gelatin in the mold and let set in the fridge.
When set, remove the wrap to use the lens. Unflavored gelatin makes clear lenses, but you can use flavored gelatin to play with colored filters, too.
How powerful is your lens? That depends on the shape and the material:
- 1/focal length = (n-1) (1/lens radius)
With a refractive index of around n = 1.38, gelatin is less refractive than glass (n = 1.51) and only slightly more than water (n = 1.33). I’ll leave it to you to combine two gelatin lenses to create a “Jell-O-scope.” When you’re done looking, enjoy your edible optics. Looks good enough to eat!