What does wool carbonization mean?

No matter how full of holes your old woolen scarf may be: it is not to be thrown away.

Behind the doors of the Comistra Italian eco-fashion factory, we carry out a traditional and at the same time extremely technological process: wool carbonization.

What does this process mean and what does it do?

How is it possible that at the end of the carbonization process, together with a series of other operations, old woolen clothes can be brought back into the haute couture shop windows?

We will find out in the next few lines by talking about the wool carbonization process which we carry out in Comistra’s plants.

We will find out together how only through this complex process we can achieve a fully circular economy in the textile sector, being respectful of the environment and careful to rationalize waste as much as possible.

Before carbonization: the disposal of textile waste

Heaps of old clothes have to go through a careful selection process before they are carbonized.

Here’s a brief of how it works:

1- the private citizen puts the old clothes, shoes, and belts in the appropriate containers;

2 – the piles of old clothes are collected and transferred to a sorting company. 40% is sent to a recycling plant (this is the group we are interested in!) and a small part is sent to an incinerator;

3- the clothes to be recycled undergo further sorting, which divides them by color shade.

(Want to learn more about this cycle from textile waste to resource? Read this article which explains what happens to old clothes when we throw them away).

In Comistra, we take care of the third step: we receive huge piles of woolen clothes and sort them by color shade.

These colored mountains constitute a mixed, hybrid product. We will have piles of jumpers and coats with cotton seams, inserts of viscose, and other cellulose fibers.

In short: a wide range of different materials.

How can we remove all the cellulose parts to obtain good mechanical wool (this is how eco-wool is called)?

This is when wool carbonization comes into our story.

What is wool carbonization

Carbonization is a process that has been known for several decades now and has been talked about in scientific terms since the 1930s. It represents the chemical phenomenon whereby organic substances lose hydrogen and oxygen and become carbonaceous residues.

There are three types of carbonization:

1) Smoke carbonization, which is used at Comistra to produce our mechanical eco-wool.

2) Soaking in sulphuric acid

3) In the rag.

What it is used for

As already mentioned, carbonization is used to remove impurities such as blades of grass, viscose, and cotton (cellulose), which would compromise the final quality of the wool. In a carbonizzo, this is how our machine is called, the fabrics are subjected to the action of hydrochloric acid vapors, which break down the cellulose residues. In addition, under certain conditions, they help to fix the color of the garments.

No need for additional dyes!

How it works

At Comistra, we have chosen to use a unique smoke carbonization machine for this operation, which does not impoverish the quality of the wool, but also carbonizes it to a very high standard and correctly fixes the color of the garments.

For a company that has made eco-fashion its flagship, it was essential to invest in optimizing resources, avoiding the costly economic and environmental step of dyeing wool.

Here is a brief description of the process:

• The fabrics are passed through a first drying cylinder, which dries them completely;
• The dried material is transferred to a second cylinder, which bathes the materials with hydrochloric acid vapors;
• During the process, which is “continuous”, the animal fibers of the wool (nitrogenous substances) remain intact, whereas the cellulose changes until it disintegrates.

After carbonization

The fabric is now free of woody excess and ready for further processing. We can send this pile of clothes to the next step of its circular economy journey, which will take it from waste to resource. Raw materials are increasingly limited, we have to take this into account. We need to review our way of consuming.