Rimbaga is the indigenous Indonesian technical term for the wax-resin-fat compound used in the à cire perdue (lost-wax) casting process to form the wax model from which a metal object is subsequently cast. The term is recorded — and the composition of the compound specified — in J. E. Jasper en Mas Pirngadie’s De Inlandsche Kunstnijverheid in Nederlandsch-Indië, Volume IV (the volume on gold- and silverwork), pp. 25–26, in a passage that Prof. T. J. Bezemer quotes verbatim in the 1933 plate-atlas to describe the casting process as practised by a Toba-Batak goldsmith on Noord-Sumatra. The passage is the immediate technical frame within which Bezemer then defines the Atjeh goldsmiths’ alternative *soeasa* wrapping technique, and rimbaga is accordingly one of the indigenous technical vocabularies through which the Atjeh goldsmithing context is documented in the late colonial Dutch scholarship.
Composition
The Jasper-Pirngadie passage, as quoted by Bezemer, defines rimbaga as “een soort was, mengsel van hars en vet” — “a kind of wax, mixture of resin and fat.” The compound is therefore a three-component mixture: wax (was), resin (hars), and fat (vet). The function of the three components is conventional in lost-wax casting: the wax provides the body and workability of the modelling material; the resin provides hardness and structural rigidity (so that the wax model does not deform under its own weight or under the weight of the clay mould); and the fat provides plasticity (so that the compound can be modelled and re-modelled in the hand and on the core). The specific proportions of the three components are not given by Jasper and Pirngadie, and presumably varied from goldsmith to goldsmith; but the three-component composition is the defining feature of rimbaga as an Indonesian lost-wax modelling compound.
Use in the cire perdue process
The Jasper-Pirngadie passage quoted by Bezemer describes the use of rimbaga in the à cire perdue casting process as follows. The goldsmith first builds the kern (the core) of the object to be cast — a clay-and-burnt-rice-bran mixture, formed and baked to shape. This core serves as a leest (a last or form) on which the wax model is built up. The goldsmith then covers the core evenly with rimbaga — “welke gelijkmatig met rimbaga … belegd wordt” — and so obtains the wassen voorvorm (the wax fore-form), the wax model that is the exact shape of the metal object to be cast. On this wax fore-form, the goldsmith models the relief decoration in further rimbaga — “waarop men eveneens met rimbaga de reliefvormen boetseert” — building up the figures, ornaments, and surface decoration in the wax-resin-fat compound. Once the wax model is complete, the goldsmith attaches giettuitjes (pouring-channels) of rimbaga to it, coats the whole with dry clay powder, then encloses it in a thicker layer of clay mixed with burnt rice-bran. The mould is then dried, the wax melted out (leaving a hollow clay mould with the negative of the original wax model, including the relief decoration, on its inner surface), and molten metal poured in through the pouring-channels to replace the wax. When the metal has cooled, the clay mould is broken away — destroying the mould but releasing the cast-metal object.
The use of rimbaga in this process is, in two respects, distinctive. First, the same compound is used both for the wax fore-form (the body of the model) and for the relief decoration (the surface modelling): this means that the relief is not carved into the wax but built up on it, in the same material as the body. Second, the use of a wax-resin-fat compound — rather than pure beeswax — gives the model a working hardness that allows it to be handled, coated with clay, and enclosed in the mould without losing its shape; pure beeswax would be too soft for this purpose in the tropical Indonesian climate.
Atjeh connection
The rimbaga passage of Jasper and Pirngadie describes the casting process as practised by a Toba-Batak goldsmith on Noord-Sumatra; it does not describe Atjeh practice directly. The Atjeh goldsmiths documented by Bezemer in the same chapter of the 1933 atlas did not, in fact, use the rimbaga-based cire perdue process for the *soeasa* wrapping technique that is the Atjeh-specific contribution to the chapter. The Atjeh goldsmiths wrapped a copper core with *soeasa* sheet rather than casting the ornament in one piece. The contrast is documented by Bezemer precisely because Jasper and Pirngadie had already documented the Toba-Batak alternative — and rimbaga is the technical vocabulary in which that alternative is described.
The Atjeh connection of rimbaga is therefore indirect: rimbaga is the technical term for the modelling compound used in the cire perdue process that frames, by analogy, the Atjeh goldsmiths’ alternative wrapping technique. The term belongs to the same technical vocabulary as spinsbek / soeasa (the alloy used in the Atjeh wrapping), cire perdue (the casting process used by the Toba-Batak goldsmiths), granuleeren (the granulation technique used by the Batak, Dyak, and Timorese silversmiths), and filigraanwerk (the filigree technique used in the Padangsche Bovenlanden) — a vocabulary that, taken together, constitutes the late-colonial Dutch technical lexicon for Sumatran metalwork, within which Atjeh metalwork is described as a regional variant.
Significance
For Atjeh’s history, rimbaga is significant principally as a piece of the technical vocabulary in which Atjeh goldsmithing is documented in the late colonial period. The term is recorded in Jasper and Pirngadie’s handbook — the standard Dutch colonial reference on Indonesian craft — and is preserved in Bezemer’s 1933 atlas as the indigenous name for the wax-resin-fat compound of the Sumatran cire perdue process. The survival of the indigenous term in a Dutch colonial handbook — rather than its replacement by a Dutch descriptive term like was-hars-vet mengsel — is itself notable: it is the kind of preservation of indigenous craft vocabulary that, in the colonial-craft-scholarship convention, was the contribution of an indigenous expert like Mas Pirngadie to the collaborative Jasper-Pirngadie handbook. The term rimbaga is, in this sense, a small piece of indigenous Sumatran craft knowledge preserved in the Dutch colonial record, and a marker of the collaborative character of the scholarship on which the AcehWiki’s Atjeh goldsmithing entries draw.
See Also
- Atjeh goldsmithing (soeasa technique)
- Spinsbek
- Cire perdue
- Granuleeren
- Filigraanwerk (Padangsche Bovenlanden)
- De Inlandsche Kunstnijverheid in Nederlandsch-Indië
- J. E. Jasper
- Mas Pirngadie
- Indonesische Kunstnijverheid (Bezemer 1933)
- T. J. Bezemer
- Noord-Sumatra
- Toba-Bataklanden
Source
De Inlandsche Kunstnijverheid in Nederlandsch-Indië, by J. E. Jasper en Mas Pirngadie, Vol. IV (on gold- and silverwork), pp. 25–26 (defining rimbaga as een soort was, mengsel van hars en vet and describing its use in the cire perdue casting process). Quoted in T. J. Bezemer, Indonesische Kunstnijverheid (‘s-Gravenhage: ten Hagen, 1933), p. 13. Universiteitsbibliotheek Vrije Universiteit, Amsterdam, LS 5411.