If seeing and smelling are not enough, it is necessary to dissolve.

In previous articles we saw some methods used to identify the textile fibres that make up a fabric no labelled with its composition. There are several identification procedures, complementing each other, that depend on the nature of the sample, on the experience of the analyst and on the available equipment.

To our fashion laboratory, where we have a complete equipment, we bring three samples that we seemingly like to make a design. We know that the choice cannot just depend on what we visually like; besides aesthetic considerations we have to take into account other aspects that will help us to foresee  the behaviour  of the fabric we are going to work with.

The samples are marked A, B, C and we start the study with a visual inspection. We take some threads out of the samples, we twist them back to get  the fibres and we observe if they are continuous filaments or they are short fibres. In the case we are dealing with, we get  filaments  from the samples A and B, and we get a short fibre from the sample C. The samples A and B may be silk or any other of the manufactured fibres and the C sample may be a natural fibre or a cut of chemical fibre. We can decide very little from a visual inspection.

Let’s go to the pyrognostic analysis burning fibres or threads of the three samples with a flame and observing their behaviour. None of them smell like burnt hair so we rule out silk. B and C smell like burnt paper and the  ashes are very light so we know they come from cellulose. A doesn’t smell like burnt paper, but we are not able to identify its scent.

Pyrognostic analysis samples A, B and C

We look at the fibres under the microscope. A and B are apparently the same, smooth and uniform, what shows us, having ruled out silk, that they are chemical fibres.

Microscope, sample A (400x)

Microscope, sample B (400x)

C presents folds and convolutions that characterize cotton, so we have already identified one of the samples.

Microscope sample C (400x)

As seeing and smelling haven’t been enough to know the composition of the three samples, we make with A and B a test of solubility with acetone. When we dip the samples into acetone we watch that A sample dissolves while B remains intact.

Solubility test samples A and B

We know that the only fibre that dissolves in acetone is acetate so we have already identified other of the  samples. If we repeat the combustion test with this sample, we’ll check that the smell that we couldn’t distinguish before is vinegar, the typical smell of the acetic acid.

Therefore, we have the exact composition of two of the samples, A acetate and C cotton. Concerning sample B we know, seeing and smelling it, that it comes from cellulose and that it is not natural. To determine if it is viscose or liocel we’ll have to pay attention to the articles in our blog. Anyway, we already have enough information to choose the material that adapts the best to our design attending to its final use.

Carmen Pardo

Photographs by Irene de Jáudenes Bernabé

Photos under the microscope by José Ignacio Pérez Tormo

Translated from Spanish into English by Edu Grao and Alicia Hergueta

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