## 2 Materials and Methods
### Structural Analysis
#### 2.2.1 Physical Tests  
Eight 10 \(\times\) 20 cm rectangular flax samples were laced according to the selected grounds (Figure 5). Seven of these samples are unique patterns, while the _Torch_ ground is repeated once as a control sample, and once with twice the number of fibres to document the corresponding strength increase. The laced samples were rolled and stitched along their short axis to create 10 mm tall cylinders with cross sections of 20 cm\({}^{2}\), which were then cast in resin and cured (Figure 6). Materials used for this test were TEX1000 flax rovings and GFK epoxy resin produced by Chemische Erzeugnisse Epoxidharz-und Hartersysteme (Firma Martin Puck Huusbargstieg 29, 22359 Hamburg Germany) with a 1-to-2 resin-to-hardener ratio. Each cylindrical sample underwent a compression test to determine their strength. Compression tests were performed in room temperature using Zwick/Roell \(Z100\) testing machine, with a test speed of 10 mm/min. The results of these tests are shown in Table 1.  
Figure 4: A variety of bobbin lace patterns and their associated graph and fabrication syntax.  
Figure 5: Lace patterns before stitching. From left to right: (**a**) A Ia Vierge, (**b**) Grille, (**c**) Quadrille Croise, (**d**) Quadrille Simple, (**e**) Toile, (**f**) Torchon, (**g**) Double Torchon, (**h**) Tulle.  
As seen in Table 1, within the six different patterns, _Quadrille Croise_ shows the best performance compared to other patterns with similar fibre amount, with _Torchon_ ranking second. The _Torchon_ pattern with double fibre was observed to fail under around double the force compared to the _Torchon_ with single fibre. _Toile_ and _Grille_ patterns, though strong, were not considered for the prototype because they create weave interactions more closely resembling woven fabrics instead of the open structures characteristic of lace. Specifically, the parallel fibre paths in _Toile_ allowed the fibre to fill the surface, causing the sample to retain much more resin than the others and thus show higher strength.  
Two issues exist in the testing process which should be better addressed in future work. First, because the samples are hand-laced, there is inherent variability in each sample. Secondly, manual stitching and resin application lead to minor deformations of some sample edges which, despite their trimming, resulted in uneven support conditions. Both factors bear effects on accuracy of the test results. However, as similar variability exists in the making of any artefact using this method, these tests suffice in providing general guidance on relative performance of each lace ground.  
One additional factor to be considered in the evaluation of patterns is the amount of labour required to fabricate [17]. As all samples except for the _Double Torchon_ have similar fibre count, production efforts in the preparation stage are similar, and the number of nodes in a given pattern is the main cause of different fabrication effort involved. This is important because while the _Quadrille Croise_ performed the best, it is also more time consuming to produce. Therefore, we proceeded with _Torchon_ as base pattern and use _Quadrille Croise_ as a reinforcement strategy in areas of higher stress.