Dammar resin is the gloss-depth and reversibility in a oil-resin varnish.

The word damar is Malay for "torch" or "resin" — a single syllable that covers an entire genus of trees and an entire forest economy. The most commercial grade in international trade, damar mata kucing ("cat's-eye dammar"), is exuded by Shorea javanica, a giant dipterocarp tree endemic to Indonesia and unknown anywhere else in the wild. Other grades — damar batu, damar temak, white and black dammar — come from sister species in the Shorea, Hopea, Vatica, Anisoptera and Vateria genera, across Southeast Asia and South India.

What makes dammar unusual is that the canonical harvest method is not extraction from wild forest but a planted forest. From around the 1880s, swidden farmers in the Krui area on the western coast of Lampung province, Sumatra, began inter-planting Shorea javanica seedlings into their rice and coffee plots. After roughly twenty-five years the Shorea canopy closes and the plot is no longer agriculture: it is forest, called repong damar in Krui, and it can be tapped for resin for two human generations. By the late 1990s the Krui repong covered around 50 000 hectares; roughly 80 % of Pesisir Barat households drew at least part of their livelihood from this multi-species, multi-storey, human-planted forest.

European industrial interest came late. Mastic — the eastern Mediterranean resin from Pistacia lentiscus — had been the picture varnish of choice in oil painting from the 16th century onwards, through Rembrandt, Vermeer and Reynolds, and would not be displaced until the 19th century. Dammar varnish was introduced to European studios in 1826, almost certainly by German restorers looking for a more stable, less polar, less rapidly yellowing alternative to mastic. Residual dammar was found in J.M.W. Turner's varnish bottle after his death in 1851; by the 1850s it was "much used in the United States." The trade has run continuously since.

Dammar is a mixture, not a single compound. Mass-spectrometry work on fresh and naturally aged dammar at AMOLF (the Dutch institute that analysed varnish from Rembrandt's Jewish Bride) identified the resin as predominantly tetracyclic triterpenes of the dammarane skeleton — hydroxydammarenone, dammaradienol and dammarenolic acid — plus pentacyclic triterpenes of the oleanane / ursane family (oleanonic aldehyde, ursonic acid, nor-α-amyrone), together with a polymeric fraction known as β-resene that accounts for roughly a quarter of the mass. The classic chemistry was worked out by Mills and Halsall in the Journal of the Chemical Society in 1956 and 1961 and remains the reference framework today.

Two physical properties matter for paint use. First, a softening point around 90 °C and melting around 120 °C (fully fluid by 180 °C), with a glass-transition temperature of about 39 °C — soft enough to fuse into a drying-oil film during cure, hard enough not to flow at any habitable indoor temperature. Second, solubility in hydrocarbon solvents — turpentine and mineral spirits dissolve dammar at room temperature without alcohol or ketone activation, which is the defining property that gives dammar its conservation value.

That solubility is the practical bridge from triterpene chemistry to paint behaviour. A dammar film does not chemically cross-link with the underlying drying-oil layer the way a polyurethane or alkyd does; it co-cures into the oil network as the oil oxidises, raising the gloss-depth and surface hardness without forming covalent bonds. Decades later, the varnish remains preferentially soluble in non-polar hydrocarbons even after extensive ageing — which means a conservator can remove old yellowed dammar from a painting without touching the oil-bound paint film underneath. Synthetic polyurethane and acrylic films, once they fail, must come off entirely. The reversibility is why dammar is still the textbook reference varnish in paintings conservation.

A cured linseed-oil film is durable, flexible and repairable, but it is also relatively soft and relatively matt. To raise the surface hardness, you can add a hard wax — carnauba does that in a hardwax-oil recipe. To raise the optical depth of the film, lift the sheen toward a satin or gloss without polyurethane plasticisers, and harden the surface, you add a triterpene resin. Dammar is the most stable triterpene resin in commercial trade. Mastic, its older cousin, yellows more aggressively and embrittles faster; the modern synthetic ketone alternatives (Regalrez 1094, Laropal A81, MS2A) outperform dammar on long-term clarity but are petroleum-derived.

Two properties keep dammar in the natural-paint toolkit. First, gloss-depth and clarity — a thin film of dammar over an oil-bound substrate refracts light deeper into the wood grain than a pure-oil film, the same optical reason mid-19th-century studio painters preferred it over mastic. Second, reversibility — the cured varnish remains preferentially soluble in non-polar hydrocarbons even after decades of natural ageing. On wood, this means a varnished surface can be cleaned and refreshed coat-on-coat without sanding the previous layer off.

Dammar pairs with linseed oil and natural-resin solvents (citrus or isoaliphatic) in the varnish-class products. Dammar is the hardness-and-gloss-depth contribution; linseed oil is the binder and substrate-key; the solvents carry the system into the wood and then leave. The recipe architecture is recognisably 19th-century and the solvent choice is recognisably 21st-century — neither lacquer nor alkyd, neither 1850s nor 2025, but the older end of a long continuity.

For a century the Krui repong damar was the textbook case of a non-destructive forest economy: a planted, multi-storey agroforest in West Lampung that produced 80 % of the world's damar mata kucing while housing four canopy layers of food trees, fruit and timber alongside the Shorea. It was the model FAO and RECOFTC pointed at when they wanted to show that resin tapping could outperform conversion to monoculture on every metric except short-run cash. That model is failing in real time.

RECOFTC and ICRAF field measurements show the Krui repong shrank from roughly 29 000 hectares in 1998 to about 6 500 hectares in 2022 — a more than 75 % collapse in a single human generation. The proximate driver is oil-palm expansion: a planted hectare of Shorea takes twenty-five years to begin yielding resin and pays a tapper modest weekly cash, while a planted hectare of oil palm yields fruit in three years and pays a smallholder in monthly bulk. The deeper driver is a 2008 Indonesian land-classification change that reduced the customary rights of repong-holding families to the trees they had planted, weakening the inter-generational economics that held the system together. Selling a thirty-year resin tree for one cycle of timber, then planting palm, became the rational private decision.

There is no clean solution we can offer from a varnish bottle in Germany. We can audit the European processors we buy from, prefer suppliers who disclose Krui-origin Shorea javanica over mixed-grade trade dammar, and write this paragraph rather than the silent-sourcing paragraph the category permits. We can refuse to claim "sustainable dammar" without a chain-of-custody certificate that does not yet exist at commercial scale. What we cannot do is solve the customary-rights problem in West Lampung from Mindelheim. The editorially honest framing is: the resin in this bottle comes from a forest economy under acute pressure, and that pressure is visible in the ingredient before it is visible in the product.