This post can also be viewed on my website: https://kanika-khanna.com/getting-nerdy-about-tea-bags/
I recently took out my foldscope from its storage bin after almost a year. But as the saying goes, it’s never too late to start exploring. I stepped out of my home into our street here in Palo Alto and took some pretty images of local flora. I will write more about them in my next post. But then me and my husband, both tea aficionados, decided to explore something already in our house. The wide varieties of tea bags in our home tea collection!
In part, I was motivated by a recent study showing that some plastic tea bags may be shedding high quantities of microplastics when placed in water heated to 95oC. Microplastics are very tiny pieces of plastic, < 5mm, and found in almost everyday items of use. It is a relatively new area of research, but recent reports suggest that microplastics pose health and environmental risks.
We had tea sachets and tea bags from 7 different companies lying about in our house and we looked them under our foldscope. There is actually a distinction between tea sachets and tea bags. A tea sachet usually contains broken and whole tea leaves and is considered as higher-quality teas. Hence, it tends to be looser in fitting with more room to expand. On the other hand, a tea bag is usually smaller, made of paper, and contains dust or fannings from broken tea leaves.
As a note, I first took images of the slide with 0.5 mm grid bars provided in the foldscope kit to calibrate all the images taken by my foldscope for measurements. All the measurements indicated the images below were subsequently performed in Fiji.
We first looked at the meshings in three tea sachets, one each from Soongachi Tea, DAVIDsTEA, and Harney & Sons Tea. Many times, sachets are marketed as “silky” tea sachets for the sake of luxury I guess, when they are in fact not made of silk. In fact, they are mostly made of food-grade plastic like nylon or Polyethylene terephthalate (PET) so that they can hold their shape in hot liquid. Based on the information provided by the respective companies on their websites, Soongachi’s tea sachets use nylon, DAVIDsTEA’s tea sachets use a bio-based 100% recyclable material, and Harney & Sons’ tea sachets use BPA-free food-grade nylon.
In the image above, you can see how the different meshes look like and their sizes for the 3 types of tea sachets. Roughly, the material for meshes had a similar width of ~ 0.04 mm for all the sachets. The openings of the meshes were largest for DAVIDsTEA (~ 0.15-0.18 mm) and smallest for Soongachi Tea (~ 0.13 mm).
Next, I turned to my paper teabags. Three of them were filled with teas from Numi Tea, Taylors of Harrogate, and Yerba Mate. One was an empty wood pulp tea bag from WINIT. You’d be surprised like me when I found out that many paper teabags, especially the pressed ones with crimped edges, also use some amount of plastic. The idea is that heat will press shut the tea bags at the edges and then the plastic will melt to seal them. Some tea bags can be folded shut and have a draw-string at the top but even they may use some amount of plastic for the added strength. Again, based on the information available on the website of respective companies, Numi’s tea bags are made of entirely plant-based materials (manila hemp cellulose, although they use a substance called PLA or polylactic acid which is derived from corns and is considered a plant-based plastic), Taylors of Harrogate use an oil-based plastic which they have started replacing with PLA. The empty tea bag from WINIT is made up of a natural, wood pulp filter.
Here are their images as seen through the foldscope below.
The Numi tea bag is like an irregular mesh of entangled fibers. I have shown two different fields of view above.
The Taylors of Harrogate tea bag is also an entangled irregular mesh network of fibers. But if you look carefully in a zoomed-in view (blue arrows in the far-right image), you can see some hollow kind of tubes that are forming a mesh of their own. In fact, they appear to be similar to the material used in the tea sachets in Image 2. Likely, these are oil-based plastics mentioned on their website.
Yerba Mate tea bag also looks like an irregular fiber meshwork. I couldn’t spot any plastic-like substances as seen in the sachets. The far-right image above is a slightly zoomed-in version of the middle image.
These empty tea bags are supposed to be made of wood-pulp fiber. But I can see some hollow tubes (blue arrows in the far-right image) which are similar in appearances to the meshes in tea sachets in Image 2. Can’t say if these are synthetic or plant-based, but found it interesting as at least their product description doesn’t mention this. The far-right image is a zoomed-in view of the middle image.
So, this was my little Sunday morning adventure with the tea bags lying around in my house. Will be great to see how the other teabags look like. I did not have a clear purpose behind doing this exercise but was just curious if I could spot any signs of plastic in tea bags that do not have a clear description. Would love to see how the tea bags of other companies look like to see if we can learn anything more about their material composition? Maybe next I will try to see if we start noticing any differences in their structure after we steep them in boiling water if I have nothing better to do next weekend :D.
Also, I learned an interesting little tidbit about the history of teabags. According to the most popular legend, Thomas Sullivan, a tea and coffee importer in New York, started shipping loose tea leaves in silk tea bags in 1908. These were actually supposed to be removed by the customers and made traditionally. But people found it more convenient to brew the tea leaves in the porous bag itself and their demand increased. Hence, the discovery of tea bags was thought to be an accident. However, few people know that two women, Roberta C. Lawson and Mary Molaren of Milwaukee, Wisconsin filed a patent for “Tea Leaf Holder” in 1903 for an open mesh woven fabric to brew tea sufficient for a single serving to avoid wastage. The principle of the apparatus resembles what we use at present, with the added commercialization of course. Just important to remember the contributions of these women too!