We’ve all heard the old saying “it’s like nailing jelly to a wall” to describe
a task that is very difficult or impossible. But is our view of the difficulty
of this task justified? Has anybody actually tried nailing jelly to a wall? In
this experiment I attempt to establish, one way or the other, the validity of
the old proverb.
I sourced the following materials from Sainsbury’s and Focus.
They are: a 16oz claw hammer, a 200g pack of 3″ (75mm) round wire nails, a
selection of 135g packs of Hartley’s jelly cubes, and a plank of wood,
dimensions 850x200x18mm (approx. 33½”x7¾”x¾”). The plank of
wood will play the part of the “wall”. The type of wood, and its exact
dimensions, are not important.
The length of the nails is important. Specifically, the nails should be longer
than the depth of the bowl intended for use as the jelly mould. This is to
enable the nail to go right through the finished jelly and into the wall without
the nail first disapparing into the jelly.
The picture below shows the proposed jelly mould (an ordinary dessert
bowl) and one of the nails next to it for comparison purposes.
A first attempt
A box of jelly, as purchased from the supermarket, contains twelve joined
“cubes”. The orange flavour is shown below. This is “concentrated” or “neat”
jelly; the idea is that water is added to produce actual jelly. Of course,
these cubes are much more viscous than the diluted mixture produced by adding
water. Therefore, it should be easier to nail the concentrated cubes to the
wall than the actual jelly.
In fact, the jelly didn’t even need a nail to stay on the wall. It just stuck
there. For good measure, I drove a nail through it. The jelly held in
This is called “cheating”.
Making the jelly
My first attempt being somewhat against the spirit of the proverb, I decided
to repeat the experiment with proper jelly. The procedure for making jelly from
the jelly cubes is documented on the reverse of the jelly boxes; a summary is
The picture below shows the equipment required: some jelly cubes (lime this
time), a measuring jug, and some boiling water.
Do not eat any of the neat jelly cubes, no matter how nice they look. They’re
incredibly sweet and probably addictive; if you eat them all you won’t have
any left for the experiment.
Pour half a pint (284ml) of boiling water into a jug, and add the cubes. Stab
the cubes indiscriminately until they’ve all dissolved. Then add another half
pint of cold water, so the jug contains a pint (568ml) of jelly mix.
Given that the intention is that this jelly be nailed to a wall, we might
intuitively get better results if we add less water than required, in order to
give a thicker and presumably sturdier mix. However, in this experiment the
jelly will be prepared according to the instructions on the packet to ensure a
Pour the jelly mix into whatever is being used for the jelly mould. In this
case, as mentioned before, we are using a simple dessert bowl. The only
restriction on the type of mould used is that its depth should be less than the
length of the nails.
If you reproduce this experiment, you will probably find that there is an
irritatingly small amount of jelly mixture left over in the jug once the mould
is full. Pour this footling amount of jelly into a glass, and place it in the
fridge alongside the bowl. For maximum confusion, don’t tell any of your
housemates about it.
Finally, leave the jelly to set overnight.
Nailing it to a wall
When the jelly has set, cover it with a plate, upturn the entire arrangement,
and carefully lift the bowl off the jelly. Then realise that the jelly is still
stuck to the bowl. Hit the bowl with a spoon a few times (to no avail) before
attacking the edges of the jelly with a thin sharp knife to loosen it.
The logical next step would be to pick up the jelly and nail it to some surface
perpendicular to the floor. Unfortunately, the first of these steps was
impossible; trying to pick up the jelly with bare hands resulted in its
partial disintegration. So, I opted for a compromise; I got the jelly back in
the bowl, and upturned it directly onto the plank, while it was horizontal.
With the plank horizontal, I drove a nail through the centre of the jelly and
into the plank.
I then added a few more nails to hold the jelly in place. Unfortunately, even
with nine nails in it, the jelly was starting to break around the nails when
the plank was tilted.
Seeing nothing better to do, I added three more nails at strategic points. When
the plank was tilted, half the jelly broke off completely and fell to the floor.
The weak points seemed to be near the nails.
The jelly’s structural integrity now having been seriously compromised, the rest
of the jelly followed about half a minute later. This attempt at nailing jelly
to a wall had therefore resulted in quite a convincing failure.
I suddenly remembered that I had more jelly. The glass into which I poured the
excess from the jug was still sitting in the fridge. I retrieved it and
extricated the jelly. Perhaps a smaller amount of jelly would nail to the wall
Taking no chances, I not only nailed the jelly to the plank using five nails,
but also added a crescent of eight nails below the jelly to catch any wayward
This worked for approximately half a minute. Unfortunately, although the jelly
that fell off was briefly caught in the crescent arrangement of nails, it fell
through the gaps after a small amount of time.
Before long, there were only trace amounts of jelly left on the wall.
Given some jelly mixed according to standard procedures and a vertical wall, it
is not possible to nail the former to the latter and have it stay there for any
significant amount of time. Furthermore, these experiments were conducted by
nailing the jelly to a horizontal surface which was then gradually tilted.
Nailing jelly to a wall while the wall is vertical is an intractable problem in
itself due to the difficulty in picking up jelly with the hands without it
Even using many nails to construct a receptacle for the purpose of catching the
jelly, which is not technically “nailing it to the wall”, resulted in failure.
This was because the gaps between the nails afford to the jelly an easy means of
egress from the receptacle.
Further research into the area might involve the nailing to the wall of a
stronger jelly mix. Alternatively, the “wall” could be placed, nails first, into
the jelly while it’s setting, to allow the jelly to set around the nails. Then
in the morning the bowl can be removed, leaving the jelly nailed to the wall.
The old proverb, then, is justified, and the reader may say that an impossible
or near-impossible task is “like nailing jelly to the wall” safe in the
knowledge that the assertion has some scientific evidence to corroborate it.