Final Assignment: Throw Away Heroes

toronto-bans-plastic-bags

Aim/Goal

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.

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Method

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.

Comments

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.

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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.

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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

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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.

 

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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.

 

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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!

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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.

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