A green coffee bean is recognized by its size, its color, its central cleft and its smell; a roasted bean still is, with more effort; a brown powder is not. Thurber puts it in one sentence in 1881: where there is grinding, there is adulteration. The 19th century is precisely the moment when coffee stops being roasted and ground at the hearth. Thurber dates the reversal within his own lifetime: a generation earlier coffee was bought green; in 1881 the United States has about 600 coffee and spice mills and more than 1,000 roasting machines, and processes 1,200,000 pounds a day. Each operation the consumer hands over is an operation in which he stops seeing.

Thurber 1881, p. 22, 25, 165; LC ch. 10

The second condition is the price gap. Coffee is expensive; peas, rye and chicory root are worth almost nothing and grow in any field in northern Europe. Walsh writes in 1894 that hardly any other article of food is so stubbornly adulterated; Thurber opens his chapter in 1881 by saying that the adulteration of coffee and the immense scale on which it is practiced are well-known facts.

Nobody reveals anything: everyone knows. Ukers, in 1922, gives the three motives for the substitute: the high price or absence of the product, the taste the consumer has acquired for the substitute, and the effects attributed to coffee drunk to excess, this last argument being the one manufacturers put forward while the other two keep them in business.

Thurber 1881, p. 162; Walsh 1894, p. 199; Ukers 1922, ch. XVII, p. 169-170

One caveat about reading applies to everything that follows. Thurber and Walsh are merchants writing for the trade; denouncing other people's fraud is also a way of selling their own reliability. Their technical descriptions are precise, but they almost never quantify how widespread the practices were: how many bags out of a hundred, in which markets, over how many years, nobody knows. Walsh, moreover, copies Thurber thirteen years later; a formula printed twice is attested only once. The processes are established; their scale remains plausible but unmeasured.

LC ch. 10, after Thurber 1881, p. 165 and Walsh 1894, p. 217