Final Assignment: Throw Away Heroes



The aim was to recreate a plastic bag with concrete casting.

Important factors or characteristics of the plastic bag that I wanted to recreate was its lightness (weight), its creases, its smooth (often) glossy surface and of course the function as a container.

The base of this research, or experiment, derives from the assignment made in the “adaptive formwork” by the concrete guru’s; Daniel Ellis Karlsson, Jakob Lif and myself, but is here a bit more explored.




The method requires: 3(!) plastic bags, sand and concrete.

The first (inner) bag is the create the void, therefore it is filled with sand to hold the pressure. It also gives the casts inside its texture.

The second (middle) bag is to contain the concrete mix and give the outer texture.

The third (outer) bag is to “suspend gravity” by giving support to the cast, it is also filled with sand. This is the least necessary bag, but without it the middle bag would want to expand to its fullest, making the cast balloon-like.


The concrete should be able to recreate the texture of the plastic bag and fill all hollows while still retaining its stability.

I used a quite standardized and common plastic bag in the series of casting: the Toppits 2 l freezer bag. According to the producer it’s very durable, easy to fill because of the flat bottom and wide opening, and also hygienic. This together with the thin plastic made it the perfect choice.


It gives a very cheap look to the cast, because the plastic lacks rigidness it creases a lot against the supporting sand. A thicker, more rigid, plastic would give a classier look.


Top: plastic foil

Middle: freezer bag

Bottom: plastic bag (big format; approx. 75×75 cm)

Casted against sand (<4 mm)


1 part Cement

0,5 part Water


I also tried with adding some pigment to distance the final product from the concrete feeling and bring it further to the plastic aesthetic.



The Story


1 part Concrete

0,5 part Water

0,01 part Superplasticizer

After trying to recreate that cast I found that that method gave a very thick and heavy cast, probably due to the amount and size of the aggregate required.



1 part Concrete

0,5 part Water

To overcome this problem I instead tried to cast without aggregate. The obvious solution! This required a change in technique. The concrete could no longer be added in the end by pouring from the top, but had to be built in the mold. I built up the cast layer by layer, with sand and cement.

The result was more in the spirit of a plastic bag than the first try, but the lack of aggregate and the very fluid concrete mix led to that much of the mix built up in the bottom and the walls only became (too) thin shells at best. This could either be fixed by a more solid mix or/and by adding some aggregate that would give the construction necessary thickness.



1 part Concrete

1 part Aggregate (sand)

0,5 part Water

So the third try was with a more sturdy mix, that wouldn’t completely give into gravity and settle in the bottom. This was the most successful attempt. Recreating the lightness, but still having some stability, evenly spread thickness, full of wonderful plastic bag creases!



1 part Concrete

1 part Aggregate (gravel (>4 mm) (first picture) or  sand (<4 m) (second pic.))

0,5 part Water

1 % red pigment for the gravel cast and 0,5 % for the gravel.


To further experiment on this method I made two more casts; one with sand as aggregate and on with gravel. I also let the supporting material of the two casts be the reverse from the aggregate. So the mix with the sand as aggregate had gravel as supporting material.

The gravel mix didn’t blend well, leaving pieces of rocks in a cement slurry, which gave to cast a very varying thickness of goods. Breaking in some parts, being too thick in some. This I think could be helped by lowering the water content.

The sand mix came out well, the only whole cast. The walls are a bit too thick to go as a plastic bag, but this could easily be helped by adding less of the concrete mix into the cast. Even though there still is to explore: were the breaking point between “thin and broken” and “thin enough and whole” is.


10/10, would cast again.

Assignment 5

Our ambition was to cast a a low cylinder shape or a circle using just a few plastic bags. With one inner bag filled with fine sand to act as a the cylinders inner form giver and outer bag to hold the actual cast. The two bags were placed in a bucket filled with sand to act as the cylinder outer form giver.


The bags and the different layers prior to casting.


The cast. A cylindrical form with two “free” plastic influenced surfaces.

Assignment 2, Group 1

mix 1

250 g cement

125 g sand (0,5 parts instead of 3)

100 g water


mix 2

250 g cement

750 g sand

25 g water (0,1 parts instead of 0,4)


mix 3

250 g cement

750 g sand

100 g water

0,25 g blue pigment (0,1% of 250 g cement)


mix 4

250 g cement

750 g sand

100 g water

0,25 g red pigment (0,1% of 250 g cement)


250 g cement

750 g sand

100 g water

0,25 g black pigment (0,1% of 250 g cement)


mix 1

The mix was very liquid, and made a strong smooth shiny sample when hardened.

mix 2

The mix was very dry. It was like wet gravel, and we could not pour it into the form but had to press it in. When hardened it was very fragile and broke when removing it from the form.

mix 3-5

The mix was wet, slow flowing, in consistency. Became hard but with a rough texture when hardened.

Due to the low percentage of pigment and low mass of concrete it was really difficult to meassure the correct amount of pigments. The low percental amount of pigment also made the change of colour almost unseeable. (From the 3 group members one could spot a difference of colour between the samples, 1 could not spot a difference and the third was unsure.) Could also not notice any difference between the three mixes in terms of consistency or texture.


Concrete embryos in wax

Group 1, Assignment 3.

Inspired by the random organic shapes created by metal-in-water casting, we wanted to see if something similar could be achieved with concrete. We carried out three tests where we would pour concrete into liquid wax, a medium with higher viscosity than water which we thought would suit the slow-stiffening nature of concrete. Would the wax allow the conrete to slowly unfold and settle, capturing its fluid form?

Concrete: The basic mix from the assignment was used, adding 2g of red pigment.

Wax: Joel Svenssons Paraffin

Test 1: Hot concrete on medium-hot wax

As it was heated, the concrete turned liquid. We then poured it over medium-hot wax, stiff enough to first support the concrete. As the concrete slowly made the wax melt even more,  concrete shapes and canals started to form. It seems like this happened mostly to the side of the jar where the wax was warmest. The final form is yet to be discovered as it couldn’t be seen through the white wax.


Test 2: Room-temperatured concrete on hot liquid wax

Concrete of normal viscosity was poured into clear liquid wax. As it entered the wax, small sausage-like shapes formed instantly and were stacked into a sculptural pile. A thin skin of white stiffening wax started to form around the concrete, making it resemble fetuses of space creatures (top picture). As the surrounding wax stiffened, we interpreted it as it would help the concrete shape to remain as it was while stiffening.

Test 3: Room-temperatured concrete on hot liquid wax (shaken)

Instead of simply letting it pile up and dry, we wanted to try to move the concrete around while stiffening, perhaps taking new shapes. However, as we shook the jar, the newly formed pile wouldn’t move at all, appearing to have stiffened instantly. Leaving the jar upside-down, we will see if time makes the concrete move a bit further.


The fully-revealed shapes will be presented later.


Ball Chair by Eero Aarnio

This chair could be made in many ways but I found the fabrication process explained by Eero himself:

“/…/ I made the first prototype myself using an inside mould, which has been made using the same principle as a glider fuselage or wing. I covered the plywood body mould with wet paper and laminated the surface with fiberglass, rubbed down the outside, removed the mould from inside /…/”

If the rammed earth is the timeless, plastic is the future. Atleast the future from the past. A strong, durable and lightweight material. I don’t know if it is the aestetics associated with the material or the material itself that interest me, but it is interesting.

Picture is from the Movie “Moon Zero Two”, taken from:

Rammed earth

Han dynasty watch Tower, China

This is a tower of compressed earth (soil). I would guess that this particular construction is made from adobe bricks, unburnt bricks made of earth.

This photograph illustrates quite well why I like this material and technique, it’s because its simplicity and poetic beauty. It’s constructed from the surroundings and when demolished or erroded it goes back into the ground. Dust, to dust. It is also intresting from a sustainable or ecological perspective.

Photo: By The Real Bear – Summer Vacation 2007, #263 – Watchtower In The Morning Light, Dunhuang, Gansu Province, CC BY 2.0,