See more photos of rosin being made.

Picture this: A rustic wedding in a California wilderness. As the guests arrive, an old-time string band tunes up-except that the fiddler is having trouble getting sound from his instrument. He rummages in his case, then freezes. "Can't believe it," he mutters. "I left my rosin at the last gig."

It might have been the start of a horrible day but for an inspired move by the banjo player, who walked to a nearby pine, pried off a lump of congealed sap, and handed it over. Brows furrowed as the fiddler pulled the horse hairs across the amber clod, then touched bow to strings. Sound! Music! And in fact the giddy newlyweds did get to dance their first waltz-though the fiddler later said he had to pick a few mummified bugs out of his bow.

But a question lingered: Could any violinist rosin up with raw pine sap? What is rosin, anyway? As it turns out, the answer lay several hours down the road in Escondido, a short way from San Diego, at the headquarters of Dodson's Manufacturing, maker of Sherman's rosins.

Jim Early runs the company now, but the outfit was started in the late 1930s, up the road in Lancaster, by his wife's grandfather, Grandpa Dodson. Dodson's buddy Pop Sherman was the local concert violinist, who for years had been making violin rosin from a recipe of his own. Sherman urged Dodson to learn the process and develop his rosin as a commercial product. The enterprise bloomed into a business capable of sustaining the family and has now been passed down through two generations. Early describes Sherman's products as "middle-grade" rosins favored by students; and many American violinists first rosined their bows with a cake of Sherman's in its familiar wooden case. The company offers a complete line for all bowed instruments, from the light amber violin product to the darker, stickier cakes for bassists.

Pine sap is indeed the key ingredient in violin rosin, and it is derived from pines grown for paper pulp on big southern plantations. A mash of pulverized trees and liquid is heated in giant "digesters" that separate the wood fibers from byproducts rich in aromatic compounds known as oleoresins. Turpentine is distilled from this mix, while the remaining "black liquor" is refined into a product called "tall oil" comprising pitch, fatty acids, and rosin-in a crude form that needs further processing before it's ready for your bow. (The same material turns up in adhesives, printing ink, rubber, and even chewing gum.) Sherman's popular cakes are made from a particular variety of unrefined rosin called Sylvaros PR R that is hard, stable, and very sticky.

Converting the raw materials to bow-ready rosin is straightforward. Early says the current process remains true to the one Pop Sherman taught Grandpa Dodson more than 70 years ago, and he still uses some of the same tools Sherman did. Various family members have tinkered with the formulas and materials over the years, but the basic recipes and techniques are unchanged.

First, Early prepares the wooden molds from long, narrow strips of sap-gum wood, each custom milled lengthwise with a rabbet, or trough: the ultimate receptacle for the rosin. Early cuts these grooved boards into matchbox-size molds-they later double as carrying cases and protective grips-then sands them smooth on a belt sander. The finished molds are lined up in neat rows and stopped at each end with rubber strips.

Next, Early chips out a measure of Sylvaros, combines it in a saucepan with beeswax and some other "secret" ingredients, then slowly heats the concoction over a large propane flame. At its hottest, around 300 degrees F, the mixture has the texture and viscosity of hot molasses. Since this cooked amalgam must cool and thicken slightly before pouring, Early uses a hand torch to keep the liquid from glazing over and to force any bubbles to the surface. Bubbles are the bane of the rosin maker, and constant vigilance is required to achieve a flawless cake. Because sap gum wood releases fewer bubbles into the hot rosin than other woods, Early favors it for his molds.

When the mixture has cooled partially, to about 225 degrees, Early lifts the pan and smoothly drizzles just the right measure into each prepared mold, wielding a scrap of tin to shield the wood's pristine edges from any drips. Once he's filled the molds, he flames each cake with the torch. The hot flame not only drives out more bubbles but polishes the surface and helps keep each cake crystal clear.

As the rosin cools and hardens, the rubber stops are peeled away and the ends torched smooth. Printed paper box tops, folded by hand, are slipped over the shiny cakes. There's no shrink wrap or other fancy packaging, and the only nod to modern marketing is a bar code, recently added. Since the rosin is at its best for a scant 18 months, every shipment of Sherman's is made fresh as the orders come in; Early maintains no inventory. That's only right, he says. A cake of rosin should spend its useful life not on the shelf but in an instrument case, where a needy player can reach it.