Table 1 Representative samples, their provenance, and dates of collection

Group I, samples labels: LR- Lingga Riau, L-Langkawi, SG- Singapore Gardens, CI-Cipetir Indonesia; fresh liquids and solids collected 2015–2019 by author

Latexes collected from trunks and leaves in Singapore, Malaysia, and Indonesia. Cis- or trans- were confirmed with NMR accordingly to plant source (Fig. 5)

Samples of natural rubber and balata prepared for analysis on microscopy glass slides and solids stored in glass vials. Cis- for natural rubber and trans- for balata were confirmed with NMR (Figs. 5, and 6)

Samples of gutta percha latex removed from under bark, Cipetir, Indonesia; trans- was confirmed with NMR (Figs. 5 and 6)

Group II, samples labels: SC-Singapore, 10-year old commercial stock, gutta percha and balata

SC1, block of gutta percha shows lip around edges from being pressed into a form. NMR confirmed trans-polyisoprene (Fig. 6)

SC2, the mottled color indicates mixture of latexes, possibly of gutta percha and balata. Identified in NMR as trans- polyisoprene (fig, 6)

SC5, the surface of block is matte, rather than resinous, indicating a mixture of latexes. NMR identified as trans-polyisoprene (Fig. 6)

Group III, samples labels: ASG Archives of Singapore Gardens, 1892–1906

ASG 51 Small, 1892, labelled as natural rubber, confirmed with NMR cis-polyisoprene (Fig. 7)

ASG 51 Medium, 1892; labelled as Manilkara, that supplied balata. NMR confirmed trans-polyisoprene (Fig. 7)

ASG 89, 1900; sample brittle, labelled as Sundik gutta, NMR confirmed as trans-polyisoprene (Fig. 7)

Group IV, early twentieth century artifacts (WC) and Tjipetir block 1917 (RS)

CW 13, Three Monkeys, an ink well, very brittle. NMR confirmed trans-polyisoprene (Fig. 8)

CW 14 commemorative medallion, brittle; NMR confirmed trans-polyisoprene (Fig. 8)

RS 1, 1917, a block of gutta percha produced in Tjipetir (Cipetir in Indonesian). NMR confirmed trans-polyisoprene (Figs.4,5,9). (Image courtesy R. Schoevaart)