About Slag

Transforming postnatural material

Slag is a complex mineral secondary product from iron and steel production. ABOUT SLAG – TRANSFORMING POSTNATURAL MATERIAL presents design approaches for an alternative way of working with blast furnace slag by transforming the material into a slag-based glass mass and metal coating in various craft and industrial contexts.
The results of the experiments are object-like material samples that illustrate the potentials of repurposing slag in different processes – enamelling, glass blowing and glass casting.
In the speculative combination and contrast of primary and secondary products, the categories into which we divide resources are questioned. Post-natural materials such as slag are an opportunity to renegotiate ideas about how raw materials will be extracted, used and perceived by the stakeholders involved in the future.

student:Max Greiner
supported by:Prof. Mareike Gast
level:Bachelor Thesis

ABOUT SLAG – TRANSFORMING POSTNATURAL MATERIAL was developed in a free bachelor project with the aim of developing concepts and visions that make blast furnace slag usable in the sense of current sustainability approaches. The aim was to reflect on how we as a society want to deal with relevant secondary resources that emerge, among other things, in the course of advancing mechanisation. Typically, blast furnace slag, a complex metallurgical secondary product, is used as an aggregate in concrete, asphalt and cement, replacing sand and clinker.
ABOUT SLAG creates a vision in which blast furnace slag (finely granulated blast furnace slag) becomes controllable and recyclable in the form of glass and metal coatings. The chemical composition and historical use of blast furnace slag suggests that it could well be worth using it in the form of blast furnace slag for the production of glass. Besides the main components silica and calcium oxide, the mining of alumina also involves considerable interference with nature. This is very often at the expense of valuable biotopes. Considerable financial resources must be invested in renaturation or recultivation. In the interest of resource conservation and nature protection, the use of slag from smelters is an obvious option.
In addition, there are several studies that confirm that the use of slags can save enormous amounts of CO2, that the melting process is supported by various chemical reactions and that other valuable chemicals relevant to glass technology (e.g. magnesium oxide) can be substituted at low cost.

Over the course of many experiments, a glass mass was produced and then processed in three different artistic processes – glass casting in plaster fireclay moulds, classical glass blowing, and enamelling. Three craft directions which, in exchange with the respective experts, allowed the slag to be translated into different contexts and to illustrate its material properties and aesthetics.
Particularly interesting is the attempt at enamelling, which reconnects the slag separated in the first process step with the metal and thus raises the primary material to a level with the secondary material and allows dialogues about the perception and classification or valuation of materials.
The idea behind the resulting material samples, specimens and more concretely designed objects is to enable the widest possible spectrum of material impressions via the slag-based glass. Different material thicknesses, surfaces, colours etc.. The results are roughly divided into three groups: Experiments, semi-finished products, objects. The experiments are partly purposeful, partly free-form. The semi-finished products ( shards, flat glass) are adapted to the form of their further processing. The objects are designed material samples that illuminate various aspects of the respective process.
Dealing with abstract, post-natural materials offers opportunities to renegotiate ideas and prejudices about material extraction, use and perception – both by the industry and by consumers. The reuse of slag as glass and coating material represents an act of transformation through which the complex heterogeneous material becomes tangible in terms of craft and design.

The time will come when such and similar anti-dissipative measures will be required in terms of resource conservation and sustainability to ensure the production of high quality materials such as glass. The extraction of sand, lime and other ingredients must already be viewed critically, which is why post-fossil futures and resources are and will remain important issues.