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The Mad Hatter: Is There Poison in Your Hat?

Mercury was used in the process of felting and that made hatters go mad. The use of mercury was banned in the 1940’s, but it is always a good idea...

While studying millinery at the Fashion Institute of Technology, I was taught that mercury was used in the process of felting hats starting in the 17th century. Water, heat, and pressure are used to transform fur fibers into a dense material. To speed up production, fur pelts were saturated in mercury salts – this process was called carrotting. Carrotting creates more tangles in the fibers and helps to separate fur fibers from the skins.

As it turned out, milliners and hat makers were unknowingly being poisoned. With high levels of toxicity entering their systems, they would begin to experience a multitude of negative long-term effects. Symptoms include but are not limited to tremors, hallucinations, anxiety, depression, memory loss, hearing and speech problems, nerve damage, vision changes, and lack of coordination. Hence the phrase “mad as a hatter” came about. In the late 19th century, scientists and the medical community began publishing their findings and provided suggestions for workplace improvements, such as better ventilation and shortened exposure times. By the early 1940’s, the U.S. officially banned the use of mercury in the production of felt.

1940's Hats


The questions I have today are: Do you wear vintage felt hats, and have you tested them for mercury? As a milliner who frequently works with and wears vintage materials, safety is always a concern of mine. For this blog post, I tested 2 fur felt hats from the 1940’s, a brown domestic peachbloom velour beret and a blue Italian fur felt pillbox. The at home mercury test kit I used can be found here.

 Mercury Testing


The mercury detection procedure is as follows:

  1. "Lightly soak a clean cotton swab with rubbing alcohol and rub it against the items you wish to test for about 1 minute.

  2. Let swab air dry to evaporate the alcohol.

  3. In a cup mix a ½ cup of alcohol using the enclosed Mercury Indicator Swab until the Indicator dissolves.

  4. On a white plastic plate place a drop of the Indicator solution.

  5. Dip the dried cotton swab into the drop of indicator solution and allow it to soak up the liquid. If detectable levels of Mercury are present on the cotton swab an orange coloration will appear on it within 1-10 minutes (depending on the Mercury concentration).

  6. Repeat steps 4 and 5 with a clean cotton swab which will serve as a reference to help distinguish the color-change." -Home Health Chemistry


Mercury Testing Results


I’ve tested items in the past, and I have discarded felt hoods I have found to be a hazard. Luckily for these 2 hats, the indicators show us that there is no mercury in the blue pillbox and a trace amount of less than 10ppm of mercury concentration in the brown beret. Both hats were tested twice, and please note that brown dye rubbed off from the beret and onto the swabs.  In the EU, the safe amount of migratable mercury in the category of metal in toys is <60ppm and <100ppm in Denmark.
I find that it is always a good idea to test vintage hats and garbs. Stay safe out there hat lovers!


Disclaimer: The information provided on the blog is for informational and educational purposes only. Binata LLC is not a medical doctor or scientist. The blog and all content, information, products and services included in or accessible from the blog are provided “as is” and without warranties or representations of any kind, either expressed, implied or statutory. Your use of this blog is at your sole risk. Binata LLC shall not be liable to you or anyone else for any loss or injury, caused in whole or part by its negligence or contingencies beyond its control in procuring, compiling, interpreting, reporting, or delivering information through the blog. In no event will Binata LLC be liable to you or anyone else for any decision made or action taken by you in reliance on such information. Binata LLC neither endorses nor takes responsibility for any products, goods or services offered by outside vendors through our blog.
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