Does Bread Really Contain Plaster Of Paris?

Long before modern internet food myths, the public harbored a deep, enduring anxiety about the commercialization of their daily bread. While modern folklore often paints the Victorian baking industry as a gruesome, deadly trade where workers were doomed to an early grave, in 1915, the headlines were shouting about a new, highly chemical terror: Commercial bread bakers were supposedly putting Plaster of Paris (otherwise known as gypsum or anhydrate) into their bread doughs. It caused serious controversy and investigations in Boston, New York, and other cities during this time. Was it true? Technically, yes…

Calcium Sulfate Hemihydrate a.k.a. "Plaster of Paris" — Calcium Sulfate Hemihydrate a.k.a. “Plaster of Paris”

Specifically, the allegations centered on the Ward Baking Company, which made Tip-Top Bread. William B. Ward also formed the Continental Baking Company, which made Wonder Bread and Hostess Cakes.

More Mineral than Flour

A Boston Department of Health official, a “Dr. Jordan,” claimed that the Ward Company was making bread that contained over 60 percent mineral matter. The idea that the bread was more mineral than flour created quite an uproar.

The Ward Baking Empire: A Quick Timeline

William B. Ward, hailing from a multi-generational baking family, aggressively consolidated the American bread industry in the early 20th century before the government finally stepped in:

1912: Opened his first independent bakery in Buffalo, New York.
1922–1925: Formed a rapid succession of massive corporations (United Bakeries, Ward Baking Company, Continental Baking Company, and General Baking Company) to aggressively acquire dozens of regional plants.
1926 (The Peak): Continental grew to 100 plants, making it the largest baking company in the U.S. Ward attempted to merge all his holdings into one mega-corporation, aiming to control a staggering 20% of all bread production in the country.
The Antitrust Bust: The federal government intervened, suing Ward for violating the Sherman and Clayton Antitrust Acts and permanently blocking his monopoly.
The Aftermath: Ward died shortly after the federal suit, forcing his massive bread empire to restructure for years to come.

Plaster of Paris Bread Dough Improver

According to The National Baker, Volume 20 (1915) several newspaper articles on the subject gave the following formula of the bread dough recipe:

Calcium Sulfate (i.e. “plaster of paris”) — 24%
Sodium Chloride (salt) — 24.9%
Ammonium chloride — 11.6%
Flour — 39.5%

That would be one hard loaf of extra-salty bread if this were the true dough recipe. But, in fact, this was the formula for a dough improver powder called Arkady flour that was added in the proportion of four pounds to a 1600-pound dough batch, so that, in reality, very small amounts of the additives were actually in the bread.

According to the Boston Board of Health, the “Plaster of Paris” powder samples obtained contained:

Calcium sulfate — 24%
Sodium chloride — 24.9%
Ammonium chloride — 11.5%
Starch — 30%

Although it does seem strange to have an ingredient used in casts, building materials, desiccants, dentistry impressions, etc. also used in bread doughs, keep in mind that these are minerals needed in human nutrition, and the names used for things differ according to their application.

Specifically, calcium sulfate is the calcium salt of sulfuric acid. When in the form of Plaster of Paris, calcium sulfate is in its hemihydrate form, meaning there is one molecule of water for every two molecules of calcium sulfate. Gypsum is the dihydrate form, meaning there are two molecules of water for every molecule of the compound. When used as a desiccant, gypsum is dehydrated in electric ovens to form the anhydrous compound.

Why is Plaster of Paris, aka Calcium Sulfate, Used in Bread Doughs?

The form of calcium sulfate used as a dough conditioner is, technically speaking, not actually Plaster of Paris, which would be quite dangerous to consume. Instead, Calcium Sulfate Dihydrate (gypsum) and Anhydrous Calcium Sulfate are used. These have been used since not only to stiffen bread dough and make it less sticky, but in the coagulation of soy milk to make tofu. It was not officially approved for use in the United States as a food additive until 1980.

Flour low in calcium is very hard to use for large-scale bread baking operations and calcium sulfate is used per regulation as a dough conditioner in parts not higher than 1.3%. It is also used as an anti-caking agent and as a leavening agent, and for this purpose, it is found in some baking powders, such as Calumet brand. It has many other uses in foods.

Calcium sulfate, besides its use in bread and other baked products, is used in grain and pasta products; some cheeses, including soy cheeses; jams and jellies as a stabilizer and thickener; candies and frostings; processed vegetable products as a firming agent; and other foods.

Calcium Sulfate (Dough Conditioner): To understand why this mineral is ubiquitous in modern commercial baking, you have to look at it through the lens of a food scientist rather than a 1915 newspaper reporter. Here is the modern technical profile of the additive that caused all the panic:

• Commercial Designations: Calcium Sulfate Dihydrate, Food-Grade Gypsum, Anhydrous Calcium Sulfate.
• Chemical Formula: CaSO₄·2H₂O (Dihydrate)
• Primary Baking Application: Dough strengthening and water conditioning in high-volume, yeast-leavened bakery products.
• Mechanisms of Action:
○ Water Hardness Correction: Commercial bakeries need absolute consistency. Calcium sulfate introduces essential calcium ions into soft municipal water supplies, standardizing the mineral balance required for predictable dough rheology.
○ Gluten Cross-Linking: The calcium ions physically interact with the flour’s gluten proteins, vastly increasing dough elasticity, machine-ability, and gas retention during the proofing stage.
○ Yeast Nutrient: Acts as a vital metabolic nutrient for commercial yeast strains, ensuring a vigorous, uniform fermentation process across massive, 1,600-pound dough batches.
• Regulatory Status (US): Designated as GRAS (Generally Recognized As Safe) by the FDA.
• Standard Usage Limits: Strictly regulated and capped at a maximum of 1.3% (by weight of flour) under current commercial baking guidelines.

The Gruesome Legacy of Bread Folklore

The Plaster of Paris panic of 1915 was simply the American continuation of a much older, deeper anxiety about industrialized food. During the Victorian era, the public wasn’t just suspicious of what commercial bakers were putting into the dough, they were horrified by the dark, subterranean bakeries themselves.

Sensational reports and growing class anxieties spawned morbid pop-history myths not just about adulterated loaves, but about the bakers making them. The folklore painted the trade as a literal death sentence, claiming that Victorian bakers were doomed to die incredibly early, gasping for breath in flour-choked cellars. Discover the truth behind the “Victorian Baker Death Sentence” myth, and why the history of the baking trade is stranger than fiction.