Resin – in beer?!

As part of my interest in historic Low Country gruit ale I took a look at the medieval gruit accounts of cities producing gruit (and with surviving city accounts). I found the majority of the 14th and 15th-century sources recorded purchases of either bog myrtle or marsh rosemary, of laurel berries and laserwort – and of (pine) resin.

Bog Marsh Laurel Laserpitium
City Dates Myrtle Rosemary Berries siler Resin
Deventer 1339-1348 X X X X
Wesel 1342-1381 X X X X
Dortmund 1390-1399 X X X
Cologne 1391-1393 X X (X) X
Zwolle 1398-1411 X X X X
Duisburg 1417 X X X
Munster 1481? X X X
Osnabruck ? X X X X
Tecklenburg 17th c X X X

Initially it was not clear what the resin what meant for: was it an ingredient,[i] or was it used to treat equipment? For instance, wood barrels were often coated on the inside with resin to make the barrel less permeable to liquids, while at the same time releasing preservative qualities, and infusing a slight resin-y flavor to the liquor.[ii] This was the initial prevailing theory – resin sounds more like a varnish than an edible ingredient – until the recipe Om Gruyt, ende Gruytbier te maken by Vorselman[iii] was taken into consideration. This recipe lists resin as part of the additives; it is included with the herbs, making it more likely resin was used as a straight up ingredient like the herbs.

The 16th century recipe Om Gruyt, ende Gruytbier te maken (To make Gruit, and Gruit beer):

To make gruit and gruit beer. Take against one pot (half a gallon of ale) a laurel berry, and also much resin, and some oat bran, and two seeds of bog myrtle. And make this beer only of barley malt, and set it with yeast.

This early 16th-century recipe indicates resin with the Dutch word appoys, which is interpreted by editor Cockx-Indestege as a type-set error for arpoys, a known variant of harpuis or clarified pine resin. In Dutch, pitch is called hars and the term for refined hars is harpoys (the silent H gives arpoys) and harpuis. Pitch is refined by melting it with heat to distill the volatile turpentine, leaving a clear resin, called spiegelhars (‘mirror resin’), with has many uses such as glue and varnishes. The term harpuis was often used for a resin mix, for instance the mixture resin and linseed oil would be painted on ships’ masts and other exposed woodwork. But it did not always mean the same; there is also note of harpuis as a mixture of resin and sulfur used to treat woodwork against woodworms.[iv] It is of interest to note that the second kind of harpuis mix of sulfured resin could add preservative qualities to beer.

In history, gruit ale had a reputation for headache causing herbals. It is conceivable that initially the herbs were specifically chosen for this headache causing effect, as part of religious ceremonies and important feasts. The herbs most often mentioned in connection with gruit all seem to have had something in common: not only do they have bittering agents which makes them more or less reliably antiseptic,[i] they also contain substances that are mildly narcotic, psychotropic, or inebriating, resulting in enhanced intoxication, and hangovers.[ii] Interestingly, the same can be said for resin. Its antibacterial effect helps preserve fermented beverages, like wine in Antiquity, and beer in the Dark Ages. And if the resin is not properly treated, the turpentine still in the resin can leach out into the ale and cause wicked morning-after headaches.

How to clarify resin

Left: pine resin, as found in nature. Right: scraped pine resin, bark residue – and bugs.

Resin is found on many types of conifer and pine trees, among other kinds. In history, it has been used as a glue (pine resin, frankincense), as a flavor (black cherry; Native Americans used it as chewing gum) and as a fragrance (myrrh, frankincense, etc), among other uses. It can be wild-harvested as found, or it can be stimulated by scoring the bark of an appropriate tree and having patience. Within a few days – weeks, seasons – of scoring the resin will drip out to cover the bark damage, like a band-aid. I had cut off a number of low hanging, otherwise dead looking branches of our pine tree to find years later – to my surprise and good luck – that the cuts had bled resin profusely. For this experiment, at least, I was all set.

The resin I used therefore was wild harvested from a pine in the backyard. It took quite some experimentation, and creative out-of-the-box thinking, to figure out a method to clarify the resin without either burning it, or getting headache inducing fumes into the house. I ended up using tin cans as a filter and capturing container, and the wood stove for radiant heat and as a ‘fume hood.’ Resin intended for brewing needs to be heated, or clarified, not only to remove organics like bark and dead insects, but also to remove headache inducing volatile turpentine.

A DIY filter


To separate resin from its organic matter and the turpentine, it is heated and filtered. Resin will liquefy when hot and can thus be run through a sieve-like filter. Turpentine is volatile and will gas off when heated and the bark & bug residue will stay behind in the filter – make sure this is done either outdoors, or ventilated. Based on a liquefaction stove design I had seen before I chose to use three metal cans; one placed into another – one as the collection chamber and the other to act as a heat shield – and one with holes poked through the bottom stacked on top to function as a filter (see photo).

How much heat is enough?

From my first experiment I learned that resin is flammable and will burn and turn into charcoal when heated too hot. The inside of the wood stove is not the right place. In front of the stove, on top of the ash tray with the door slightly ajar for maximum radiant heat turned out to be the ideal setting. And this way the volatile turpentine gases also mostly go up the chimney (be aware, these gases are headache inducing).

Left: The stacked filter freshly loaded with bark-y resin. Right: the resin has mostly dropped through and the bark is out of sight.

The 16th century Gruyt recipe describes resin as arpoys, a middle Dutch word for spiegel hars, or ‘mirror resin.’ When looking at the clarified resin, it sure reflects like a mirror!

When the resin was suitably liquid it was carefully poured into a silicone mold. But getting the stuff back out did not work as well as hoped for: it is both brittle, like glass, and sticky, like caramel. If you do not have time to let it harden, then cold water might do the trick.

As I needed measurable pieces of resin on short notice a new process was devised: pouring the hot resin into cold water, which would instantly solidify the resin. Not only did this make small pieces of resin, it also created rather pretty shapes, reminiscent of Chihuly glass sculptures.

From leaving a pint jar with resin on the kitchen table – in the sun – I also learned resin should be stored in a plastic wide mouth container, out of sunlight and away from heat, as it will become sticky again and clump together.



When we used the clarified resin in our Gruit ale, version 1 (see image left) we came to an unexpected conclusion: not only does the resin not taste odd, it seems to enhance its surrounding flavors. In our blind taste test; invariably the gruit ale with the resin was picked out as the best tasting. Maybe Dark Age intuitive brewing has more going for it than modern (chemistry) brewing would like to give it credit for!