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Cordage experiment at La Ciutadella Ibèrica de Calafell

Date: 
Wednesday, 13 May, 2015 to Sunday, 11 October, 2015
Responsible: 
Jasna Lesnjak
Number of Participants / Visitors / Audience: 
8

INTRODUCTION

In June 2014, during the OpenArch conference in Kierikki (Finland), the delegates from the Department of Archaeology of the University of Exeter chaired a session about collaboration possibilities within the OpenArch partners linked to the workpackage the Dialogue with Science.

They prepared protocols on some aspects for a joint experimentation. La Ciutadella Ibèrica de Calafell was especially interested to collaborate in an experiment related to cordage with vegetal fibres.

Thanks to OpenArch we could train members of our staff to develop activities about cordage in our museum. Therefore from Spring to Autumn 2015, one of the educators, Jasna Lesnjak, who has increased her knowledge on the processing of vegetal fibres during the project implementation, she coordinated the experiment works following the protocols under the monitoring of Dr Linda Hurcombe from the University of Exeter, in order to achieve the results. Originally, the material suggested in the protocols was processed hemp, however as the Iberians worked with esparto grass we also decided to test with this fibre.

KEY VARIABLES

material (esparto, hemp) and technology (plait and 3 strand S ply).

RAW MATERIALS

- crushed esparto fibres, bought in south of Spain, storage conditions: dry. Crushed esparto is a raw esparto submerged into water for until 40 days, dried and crushed in order to obtain more flexibility; no heckling is applied at this stage. These fibres are aprox. 50cm long and strong enough to be used by farmers for tying/stacking crops just as they are (without being transformed into cordage previously), and also can serve for making simple handmade cordage.

- processed hemp – provided by the University of Exeter, storage conditions: dry, heckled.

AIM OF THE EXPERIMENT

Our aim was to compare the resistance of esparto and hemp cordages/ropes, made by two different techniques (plait and 3 strand S ply), in five types of thickness. There were 3 samples of each model made.

Our intention was to investigate first the performance of cordages/ropes just as they are when recently made (without being used).

The next step would be to expose them to different conditions of use (indoor, outdoor, sunk in water, sunk in sea water, carrying constant weight) during a longer period of time (at least 6 months), in order to research their performance in time and compare these results with the ones obtained with cordage/rope when new. Unfortunately, there was not enough time available for performing this second part of the experiment, so we have to limit ourselves just on the first step (exploring the samples recently made).

EXPERIMENT DESCRIPTION

ESPARTO CORDAGE/ROPE: We decided to make the esparto cordage/rope examples only as long as the length of the esparto fibre permits, avoiding adding new fibres while plaiting/plying in order to be able to control the exact number of fibres used in each piece and this way be able to find out if the strength of different thickness models will also grow exactly in the same proportion as the number of fibres used in them does.

In each material and technique applied there were 5 different thickness types made. The thickness is constantly doubling, because the number of esparto fibres used in each model doubles between a thinner one and the next (thicker) one. In the thinnest model there’s 1 fibre in each of 3 strands, while in thicker ones there are 2,4,8 o 16 fibres per strand, being the total number of fibres used in these cordage/rope pieces: 3,6,12,24,48. We considered that it would be interesting to find out if the strength of these models will be growing exactly in the same proportion as their thickness does and if there will be any differences between the two techniques used.

HEMP: On the other hand, we repeated these models also in another material, processed hemp provided by the Exeter University. As these fibres were much thinner (they were provided to us already heckled), in this case we could not count fibres in order to control the thickness of the rope, so we tried to achieve the same thickness as in esparto models by measuring the diameters of hemp cordages/ropes and trying to make them as close as possible to the thickness of esparto ones.

VARIABLES/POSSIBLE COMPARISONS

As our cordage/rope samples are made of two different materials, by two techniques and in 5 thicknesses, we consider it would be interesting to compare:

- the strength of the same technology/thickness models made of two different materials (esparto vs. hemp);

- the strength of the same material/thickness models made by two different techniques (plait vs. ply);

- the strength of the same material/technique models among 5 different thickness models; find out if the strength grows in the same proportion as thickness does.

LABELING EXPLANATION

ESPARTO MODELS:

MODEL EXPLANATION
E-3F/PLAIT ESPARTO, 3 FIBRES (1 per strand), PLAIT
E-6F/PLAIT ESPARTO, 6 FIBRES (2 per strand), PLAIT
E-12F/PLAIT ESPARTO, 12 FIBRES (4 per strand), PLAIT
E-24F/PLAIT ESPARTO, 24 FIBRES (8 per strand), PLAIT
E-48F/PLAIT ESPARTO, 48 FIBRES (16 per strand), PLAIT
E-3F/PLY ESPARTO, 3 FIBRES (1 per strand), PLY
E-6F/PLY ESPARTO, 6 FIBRES (2 per strand), PLY
E-12F/PLY ESPARTO, 12 FIBRES (4 per strand), PLY
E-24F/PLY ESPARTO, 24 FIBRES (8 per strand), PLY
E-48F/PLY ESPARTO, 48 FIBRES (16 per strand), PLY

HEMP MODELS:

MODEL EXPLANATION
H-3/PLAIT HEMP, PLAIT, same thickness as esparto model E-3F/PLAIT
H-6/PLAIT HEMP, PLAIT, same thickness as esparto model E-6F/PLAIT
H-12/PLAIT HEMP, PLAIT, same thickness as esparto model E12F/PLAIT
H-24/PLAIT HEMP, PLAIT, same thickness as esparto model E24F/PLAIT
H-48/PLAIT HEMP, PLAIT, same thickness as esparto model E48F/PLAIT
H-3/PLY HEMP, PLY, same thickness as esparto model E-3F/PLY
H-6/PLY HEMP, PLY, same thickness as esparto model E-6F/PLY
H-12/PLY HEMP, PLY, same thickness as esparto model E-12F/PLY
H-24/PLY HEMP, PLY, same thickness as esparto model E-24F/PLY
H-48/PLY HEMP, PLY, same thickness as esparto model E-48F/PLY

Images

Staff training
Doing the first ropes
Staff training
Jasna explaining further steps of cordage...
Checking thickness
Samples of material
Results