according to the Clinton Public newspaper,1885, this is how the scam worked:
The operators are generally women, although employed and directed by an agent of the other sex, and their method of procedure, as explained by several ladies who have been victimized, is as follows:
These women call at private residences and maneuver to get access to the kitchen, where they introduce the subject of baking powders, inquiring the kind used in the family. Being shown the can, perhaps a fresh full one, they volunteer to “test” it to ascertain its qualities. Their “test” consists of placing the can on a hot stove or over a lamp or gas jet. If the baking powder is good for anything the heat will, of course, expel the gas, which, being ammoniacal or carbonic, is apparent to the sense of smell. The claim is then made that this odor indicates something detrimental, although, as a matter of fact, a baking powder that would give off no gas when subjected to heat would be without leavening power and valueless. Circulars are left with the housekeeper condemning the brand of baking powder tested, and putting forth the claims of some other brand as the “only pure,” etc.; or the new baking powder is offered for sale, or orders are taken for it to be turned over to the family grocer. Were this the whole of the trick, housekeepers would not often be deceived. Every intelligent person knows that baking powder is not made to be used in this way, but in a mixture with flour and water, where its action is entirely different from that produced by dry heat. But the chief object of this jugglery is to destroy the baking powder given for testing; or by heating it to drive off its leavening gases, and so weaken it that when used it will fail to work. At the next baking there is heavy food, of course, and the tramp probably gets the credit of having told the housekeeper a valuable fact, instead of having spoiled her baking powder, as was actually the case. The average “tramp” will, in this way, destroy from fifty to seventy-five pounds of baking powder a day. A second method of spoiling for use the baking powder in a kitchen where they are not permitted to experiment with it, is by dexterously throwing in a the can a small quantity of salt, soda, or powdered lime. Again, should there chance to be no baking powder in the house, the operators will produce, of the kind used by the family, a sample that has been purposely adulterated or “doctored” to make such an exhibit as they desire under the so-called test. The only way to protect our food from being contaminated by tramps of this kind is to turn all persons who wish or attempt to tamper with it unceremoniously from the door, and to use those articles, only, which experience has proved satisfactory, or the official tests have established as pure and wholesome.