How To Make Ice Cubes Shaped Like Tiny Baby Heads
When
it comes to serving a chilled drink, you can use cube-shaped ice like
adults do—or you can show your eternal youth with custom ice replicas of
your favorite toys. With a few basic supplies and a bit of patience,
you can make a reusable mold to cast frozen replicas anything—even a
baby doll head that's just about the right size for a rocks glass.
You Should Do This If:
You love Batman so much you actually want to ingest him.
Moment of Satisfaction:
Watching a block of ice shaped like a human head slowly melt into a glass of bourbon.
Biggest Pain in the Ass:
Not being able to reenact the latest
Avengers trailer while waiting for Mjölnir's silicone grave to firm up—some mixtures can take up to a week to cure.
Materials and Tools Required:
- Small, hard toy without too many hollow features
- Container that closely but entirely fits toy
- 10-ounce tube of clear 100 percent silicone caulk (but not "Silicone
II"), caulking gun, and cornstarch (or use Sugru or a catalyst-driven
food-safe RTV silicone from Smooth-On)
- Popsicle sticks
- Plastic cups, spoon and knife
- Non-stick food spray (canola oil worked well)
- Wax paper or aluminum foil
- Duct and masking tape
- Nitrile gloves
- X-acto knife of sharp box cutter
- Well-ventilated work area and/or high quality filtered respirator
Difficulty:
On a scale of one to ten, five.
Cost:
About $20 if you mix your own silicone. Lots more if you buy the real stuff.
Building It:
1. Set up a mold box. I did two castings: The
decapitated head of a baby doll from the 99-cent store, and a Storm
Trooper. Each required different molding techniques—a firm, two-part
mold for the figure, and a one-piece, supple, peel-able mold for the
baby head.
For the Storm Trooper, I used a plastic storage box for cream cheese
that left about 1/4-inch of silicone on all sides. A quart-sized plastic
yogurt container fit the doll's head. You can also use Legos or a duct
tape-lined cardboard to build a mold box. Professionals make theirs out
of high-quality plywood. Just don't pick something much larger than your
object or you will waste silicone.
2. Plan placement. Because of their pesky limbs,
figurines need to be cast with a two-piece mold, otherwise you would
never be able to extract them from the hardened silicone. They work best
when molded front and back, with the seam running down the side.
All molds need an opening (called the sprue) where you can pour in
the casting material. I affixed a segment of a plastic straw to the back
of the Storm Trooper for mine. Air holes at the ends of long narrow
sections (legs, arms) help the water flow through without getting
blocked—toothpicks work well for this. And look out for narrow segments
on limbs; the skinny joints on my Storm Trooper's knees caused weak
spots that broke easily when the ice was removed. Reinforce those areas
by adding putty to thicken them up before making the mold.
Deeper objects with less extremities (like the baby's head) can work
in a one-piece mold made from a softer mix of silicone, then peeled off
after casting. Sometimes cutting the mold will be necessary to get past a
tight sprue. I let the neck of the baby head extend out of the silicone
as my spot to pour in the liquid, and then cut it halfway apart when
taking the head out.
Once the container, sprue, and placement are determined, give
everything a healthy spray of canola oil. This will help keep the
silicone from becoming permanently stuck.
3. Mix silicone. Note: Although inert, most silicone
caulk isn't listed as food safe, nor is Sugru (although they're working
on FDA approval). There are varying reports that once cured, the
widely-available GE Silicone I (but not Silicone II) may be okay for
this type of use, but if you don't like living on the edge, get a food
safe silicone putty like this stuff on
Amazon.
Standard silicone caulk, poured thick, will remain liquid on the
interior—not useful for mold making. You can force it to harden
throughout by mixing the silicone with cornstarch (as pioneered in this
Instructable by Mikey77),
which provides the necessary moisture needed for the silicone to
completely harden. But when it does, it releases a strong acidic odor,
so make sure to have good ventilation or a good respirator for this
part. And use a sheet of aluminum foil as a work surface, instead of
gumming up your dining room table. I wrap a piece of plywood with foil
for a transportable work surface.
For a fast-curing, firm rubber mold, use one part silicone to two
parts cornstarch—squeeze the silicone into a cup, shake the cornstarch
into two similar cups, then pour everything into a larger container and
mix thoroughly with your plastic spoon, knife or Popsicle stick. It
might seem that there is too much starch for the silicone, but keep
mixing and cutting through it and eventually it will all absorb and
you'll have a sticky, wet paste. You can also mix this by hand right on
your work surface, like kneading pizza dough. Wear gloves. Keep a small
dish with cornstarch nearby for dipping, and the silicone won't stick to
your gloves. This mixture only takes a couple minutes to start getting
hard, so be prepared to work quickly.
For a runnier batch of silicone, use the reverse ratio (two or more
parts silicone, one part cornstarch) and add in one part distilled
water. This mix will flow over details easier and minimizes troubling
air pockets, but will take longer to cure—possibly a lot longer.
4. Mold a toy. For the Storm Trooper, place a layer
of the silicone mix on the bottom of the plastic container, thick enough
to cover the front half of the figure. While still supple, carefully
but firmly press the oiled figure into the silicone. The goal is to get
all of the figure's details surrounded and covered, without gaps or air
pockets. But make sure you don't push it all the way through. Get an
even level of silicone around all sides, as close to the halfway point
as possible, without any parts fully covered. This will make extraction
easier.
While still hardening, use the edge of the Popsicle stick to press a
1/8-inch deep impression around the figure, tracing its details but not
touching it. This will be the key that will help keep the top of the
mold perfectly aligned, and will also act as a gasket to keep water from
squeezing out or having excess ice flashing where the two halves meet.
For the baby head: start by lubing it well with oil (which might be
the creepiest thing you'll ever do). Then goop a thin silicone coating
onto the entire exterior of the head up to the neckline, making sure the
details are perfectly coated. Pour the silicone into the bottom of your
plastic container, then push the coated baby head into the silicone,
adding more to fill up the container as needed. There is potential for
large air bubbles to get trapped inside the silicone during this part,
which will cause undesirable voids, so be careful to pour and mix it in
smoothly. Allow the neck to remain exposed and set this aside to firm
up.
5. Wait. For the thicker silicone/cornstarch mix,
this should be firm in about 30 minutes. For the thinner mixture, it
took about five days to reach the right firmness.
6. Make a mold top. (This is for the two-part mold
only.) Once the front half of the mold feels solid, give everything
another coat of nonstick spray. Forget to do this and you'll probably
never get your toy out from the two halves. Mix up another batch of
one-to-two silicone/cornstarch, and working quickly, press the mix
firmly into the container, working from one end towards the other to
surround the figure while avoiding pesky air pockets (use those
cornstarch-powdered gloves for this, or spritz them with oil). Allow the
sprue and any toothpicks for air holes to remain exposed, and if you're
picky about things, use the back of the plastic spoon (lubed with oil)
to smooth the top of the silicone as it cures. Bonus points if you slope
the silicone inwards towards the sprue and air vents.
7. Remove the original. The hardened silicone will
have the tendency to stick to the container. You'll have to start
working it loose—a few spritzes of canola oil between the plastic and
silicone (spread apart with an oiled Popsicle stick) helps things
drastically. If you made your own box out of legos or wood, simply
disassemble it.
Take out the object you are molding and inspect the inside of both
sides of the molds. No air pockets or voids? Keyed gasket filled in?
Holds together nicely when put back together? Good job.
For the stretchier, one-part baby head mold, press around the
silicone to find the thickest area. Then, from the neckline, carefully
cut a line towards that side. Get a sense for how far you'll have to cut
to remove the head without tearing the mold. Some spritzed canola oil
helps with the release. Looking back, I could have probably made a
smaller cut for mine.
You should now have a mold with an inverted duplicate of your toy.
8. Freeze stuff. Clean your mold with warm soapy
water, just to be safe. Close the mold and wrap some tape or rubber
bands around it to keep it sealed, but not so tight that the rubber
distorts. For the opening on the mold for the baby's head, a few pieces
of tape were placed to seal the rubber.
Fold a long piece of duct tape onto itself and place under the mold,
extending outwards. Stick this into the same container used to make the
mold. The container will help make sure the mold maintains its shape,
and the duct tape will act as a handle to help remove it when taking it
out of the freezer.
Carefully pour water into the sprue and let it flow up until you see
it start to peek out of the air holes. This is where the sloped exterior
comes in handy, keeping any spills from getting all over the outside of
the mold.
Carefully put this in your freezer, and wait a few hours. The
insulating silicone rubber makes it to take longer to freeze, but also
helps get a clearer piece of ice. Small pieces like the Storm Trooper
take about three hours; the baby's head took twelve hours and still had
some liquid on the inside.
9. Party. Put your creation in your favorite
libation and feel the incredible freedom of never having to cool your
drink with cube-shaped ice again.
Don't have time to make your own? You can get one of these, custom-made, by me, in my
online store.